[GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

[MICHAEL FOSTER]

A reputable shop here wants to charge $195 to rebuild my QUADRAJET when I bring it in to them. This includes new shaft & bushings, setting up carb/ fuel level, accelerator pump etc.,

Looks like a Dick Patterson rebuilt carb costs about $390 plus shipping charges from our GMC suppliers.

TBI (throttle body injection) Howell can be purchased (but not installed) for about $1100.00

Any differing opinions about the value of each? Where best to spend money.

Michael
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[Jim White]

Michael-
I had a Paterson Rebuilt Carb (and distributor) installed exactly one
year ago and my engine runs like new since then.
No way I would let any local rebuild my carb and this from a guy who has
rebuilt dozens of British carbs dating back to 1931 SU's.
I wouldn't screw around with TBI unless I live at 8,000 feet and had an
FI expert living next door.
You can spend a fortune just analyzing problems with a TBI.
JMHO-
Jim "Doc" White
Wintergreen, VA
75 GMC Stretch (with Paterson Carb & HEI)
**************************

[scott cowden]

Mike;

Listen to the Doctor. Carbs aren't perfect, but they're simple and with basic maintenance will pretty much always get you where you want to go.

I too, have a Paterson carb and distributor. The coach idles more smoothly than my mid-90's pickup with full ECM control. not a miss, not a burp, not a fart. the damn thing even sounds more evil than my old corvette! [love that series 70 muffler]

Think of the ROI on a $1500 EFI system over the 3k miles per year the average RV travels. And if the 'net is any indicator, the EFI converted guys aren't having any fewer problems than anyone else, just different and more complex ones.

just my northern red-neck two cents worth.

Scott '74 ex-Glacier Orillia, ON, Canada

> Date: Thu, 24 Sep 2009 18:43:30 -0400
> From: james...@cyberwind.net
> To: gmc...@temp.gmcnet.org
> Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

_________________________________________________________________
New! Open Messenger faster on the MSN homepage
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[Gary Berry]

When I checked on the Dick Patterson carb, it was like $390 for the
rebuild, and that was if you had a good core carb. There was another
$300 for the core. So I figured for mine, it was going to cost almost
over $700 with shipping. I got the Howell for $1100. I just figured I
would go with the new stuff. Just be careful of the core charge is
all.

--
Gary and Diana Berry
73 CL Stretch in Wa.

[Jim White]

Gary-
Dick told me that my core was good before I spent a penny. In fact you
can determine that yourself if you know what to look for.
Doc

Gary Berry wrote:
> When I checked on the Dick Patterson carb, it was like $390 for the
> rebuild, and that was if you had a good core carb. There was another
> $300 for the core. So I figured for mine, it was going to cost almost
> over $700 with shipping. I got the Howell for $1100. I just figured I
> would go with the new stuff. Just be careful of the core charge is
> all.
>
>

[Jim Galbavy]

I'll second Doc and Scott for all of the same reasons. I have my GMC to travel in, not to trouble shoot in the driveway or on the side of the road. I live in Virginia (well below 8,000 ft.). My GMC gets me there and back without issues. ... having said that Mr. Murphy will now be on the lookout for me.

jim glabavy
'73 X-CL (ANNIE)
Chesterfield, Va

[Ken Henderson]

Michael,

I'm not carb expert by any stretch of the imagination. But before letting
anyone rebuild a GMC carb, I'd ask what size main jets and what metering rod
numbers it should have. And what power valve spring it should have. I'd
probably also ask whether they'd set up a Toronado carb to go on the GMC.
If they don't know the answers to the first two Q's, or agree to do the 3rd,
no deal because they don't know the GMC.

Ken Henderson
Americus, GA
GMCWipersEtc.com
'76 X-Birchaven

[Ken Henderson]

What's this "... fewer problems than anyone else, just different and more
complex ones" foolishness? We ain't havin' no steeekin' PROBLEMS! Just
"fun" & "opportunities to excell"! :-(

Ken H.

-----Original Message-----
...

Think of the ROI on a $1500 EFI system over the 3k miles per year the
average RV travels. And if the 'net is any indicator, the EFI converted
guys aren't having any fewer problems than anyone else, just different and
more complex ones.

just my northern red-neck two cents worth.

Scott '74 ex-Glacier Orillia, ON, Canada

_______________________________________________

[Gary Berry]

See, the problem with mine is that I have an Edelbrock carb on the
Stretch, and Dick wasn't going to take that as a core, so checking and
knowing what to look for wasn't going to make a difference. The
Edelbrock runs good, gets good mileage, starts everytime on the
electric choke, and doesn't vaporlock. But, my brother has a bad stock
carb on his Palm Beach, and since the Edelbrock is still working, I
think we're going to put the Howell on his coach. All I was trying to
point out is that there is a hidden core charge if the carb you send
doesn't meet Dick's expectations. With that and the cost of the
rebuild and shipping, you're just getting close to a system yoiu can
get through JR Wheeler. I'm done with this.

On Thu, Sep 24, 2009 at 4:39 PM, Jim White <james...@cyberwind.net> wrote:
> Gary-
> Dick told me that my core was good before I spent a penny.  In fact you
> can determine that yourself if you know what to look for.
> Doc

--

Gary and Diana Berry
73 CL Stretch in Wa.

[Shan Rose]

if you have the money go with the EFI will be pretty much self tuning, and generally is a bit more effecient then a carb.

im not afraid of EFI, its pretty easy to figure out once you get the hang of it, hell I even made my mustang run off of E-85 with some larger injectors and a little programing of the factory tune and altering the fuel slope then burning the chip. sounds complicated but really wasnt...

[Dennis Sexton]

Michael,
The GMC original carbs don't always need the staft work because the carb doesn't get the workout a car carb does. Sometimes you just need a few new gaskets to stop any leak issues.
If you plan to have someone do the work for you Dick Paterson is no doubt the best. If you deal directly with him, he can determine what use you have and make sure you get a carb appropriate for your needs. He is probably attending Pueblo at this time (and usually has a few carbs for sale). Check Gene's site here..

http://gmcmotorhome.info/engine.html#quadrajet

to see if you have an original carb which will serve as an acceptable core.

Good luck,
Dennis
--
Dennis Sexton
73 Painted Desert 230
Germantown, TN

[Mr.erf ERFisher]

here were my reasons for upgrade to a TBI

*MY REASONS FOR UPGRADE*

20 Year upgrade in technology
No more dieseling at shut down or slapping the gas 10 times to start
No more sticking choke and other linkage
Get rid of the Carb input filter connection
No more leaking / varnished linkage, floats, jets, set screws, etc
Closed loop control of combustion for altitude, gas, engine
condition, etc
Module swap repair of system, i.e. , injectors, computers, sensors,
etc
Electronic diagnostics
No new Quadrajet carburetors available, no upgrade possible with old
system
Technology proven in all modern engines since about 1986

must say, I was very embarrassed when ever I came to a stop in a campground
and the GMC would diesel on for several minutes then backfire with a big
black cloud of smoke out the back (also ruined 2 muffler sets).

JWID

gene

> Any differing opinions about the value of each? Where best to spend money.
>
> Michael
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Jim White]

Gary-
It's true that you need an appropriate core to replace any auxiliary
these days. In your situation, you can always find a Rochester Q Jet at
the Men's Mall. I have had EFI on two Caddys and on my Envoy and they
are great until they require maintenence. There's no way I would put an
aftermarket EFI on my GMC since I can't work on it. Seems like even
JimK has dificulty keeping his running.
JMHO-
Jim "Doc" White

Gary Berry wrote:
> See, the problem with mine is that I have an Edelbrock carb on the
> Stretch, and Dick wasn't going to take that as a core, so checking and
> knowing what to look for wasn't going to make a difference. The
> Edelbrock runs good, gets good mileage, starts everytime on the
> electric choke, and doesn't vaporlock. But, my brother has a bad stock
> carb on his Palm Beach, and since the Edelbrock is still working, I
> think we're going to put the Howell on his coach. All I was trying to
> point out is that there is a hidden core charge if the carb you send
> doesn't meet Dick's expectations. With that and the cost of the
> rebuild and shipping, you're just getting close to a system yoiu can
> get through JR Wheeler. I'm done with this.
>
> On Thu, Sep 24, 2009 at 4:39 PM, Jim White <james...@cyberwind.net> wrote:
>
>> Gary-
>> Dick told me that my core was good before I spent a penny. In fact you
>> can determine that yourself if you know what to look for.
>> Doc
>>
>
>

[Ken Henderson]

Jim,

After a LOT of trying, Dick Paterson has given up on making other than GMC
Quadrajets work. Even Toronado QJ's are sufficiently different that they're
not satisfactory even with the correct jets, needles, and power valve
spring. He reports <50% success with Toronado carbs. Seems lots of
passages are different and even with his flow bench he couldn't get good
results. 'Least that's what he's told me during several converations.

Ken H.

-----Original Message-----
... In your situation, you can always find a Rochester Q Jet at the Men's
Mall...
Jim "Doc" White

[Terry Taylor]

The VAST majority of Jim K's fuel injection issues were related to a
different issue that was
causing his (very old, impossible to repair) computers to fail. His new
Holley EFI computer
is fine, just needs some tuning. His current problems are not fuel
related, but engine issues.

Jim White wrote:
> Gary-
> It's true that you need an appropriate core to replace any auxiliary
> these days. In your situation, you can always find a Rochester Q Jet at
> the Men's Mall. I have had EFI on two Caddys and on my Envoy and they
> are great until they require maintenence. There's no way I would put an
> aftermarket EFI on my GMC since I can't work on it. Seems like even
> JimK has dificulty keeping his running.
> JMHO-
>
>

--
Terry Taylor

Web Site: http://store.n6mon.org
Store Site: http://www.n6mon.org/zen-cart
Blog: http://www.n6mon.org/blog

[Chris Choffat]

This one gets me too. I like the simplicity of TBI, The best chevy truck I ever had was a 90 silverado with a 350TBI. Went like Stink.

I hate the pumping of the carb. I hate the leaking, but then there is the simple fact it is a simple carb that anyone including Myself, can work on.

I got a chance to drive the "Green Thing Party Bus" GMC that I posted in the photo site a while back. Drove it yesterday. It has been sitting for 6 weeks without moving, two dead batteries, but it fired up with as soon as I turned the key with a car dealership jump start thingie. It has TBI.

It starts easy. Idles well. but in the acceleration department, my 115000 mile tired 455 with the leaking Qjet that the accelerator pump no longer works will out accelerate that green thing anytime. I can do burnouts with it just after it bogs from the secondaries opening and no squirt of gas initially.

I'm now more confused than before... :roll:
--
-Chr$
77 Kingsley 455 Under painstakingly long Rennovation
Scottsdale, AZ

[MICHAEL FOSTER]

I should have noted that my 78 Birchaven has a 455 motor and GMC Motorhome 455 carburator. So a local rebuild would be utilizing all the correct GMC stuff.

[Jim White]

Ken-
I'm no authority on GMC MH carbs, but was under the impressions that
there were two different carbs used on the TZEs.
One was a Rochester and I'm not sure what the other was. I've heard i
referred to as a GMC carb. I know that Dick took one look at my carb as
said, "that's a good one."
Please excuse me if I mislead anyone.

Jim "Doc" White
Wintergreen, VA

75 GMC Stretch (with Dick Paterson carb of some origin)

[dennis...@aol.com]

Jim,

The GMC MH carbs were rochester quadrajets -- go here to see the numbers on the specific carbs by year...

http://gmcmotorhome.info/engine.html#REBUILD

Dennis

Dennis Sexton
73 GMC
Germantown, TN
USA

-----Original Message-----
From: Jim White <james...@cyberwind.net>
To: gmc...@temp.gmcnet.org
Sent: Fri, Sep 25, 2009 7:51 am
Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

[Gary Casey]

I'd forgotten all about dieseling until I brought my "new" '73 home.  Here are some of the tricks the experts at GM used to recommend:

1.  Make sure the idle speed is as low as possible.  Idea is to get the engine to stop turning before it has a chance to diesel
2.  Shut the engine off under load.  I always shut mine off in gear.  Same idea - the extra load lowers the idle speed and slows the engine faster.  If you could get the AC compressor to engage that would help, too.
3.  Rev the engine up and the turn off the key.  This is the opposite approach - get enough cool air to flow through and cool off the hot spots before the engine slows down to "dieseling speed.".
4.  Go to full throttle after turning off the key.  Idea here is to lean out the mixture so it can't fire.  Problem is that the pump shot puts in more fuel and until the engine slows down to idle speed or lower the mixture is still rich.
5.  Pump the throttle after turning off the ignition.  Idea here is to richen the mixture so much the fire can't propogate.
5.  Add an anti-dieseling solenoid.  This added air below the throttle to lean out the mixture.
6.  Add a (different) anti-dieseling solenoid.  This version closed the throttle further, reducing air flow.
7.  Pull the heads and clean off all the carbon build-up.  This works for a little while.
8.  Replace the heads with aluminum ones.  This reduces the surface temperature.

The old big-bore engines with cast iron heads seemed to be especially prone to the problem.  As you can see, some of the suggestions contradict others.  The problem was never totally solved until EFI was introduced, which shut the fuel off to stop the engine.
gary

[David L Greenberg]

On Fri, 25 Sep 2009 08:51:12 -0400 Jim White <james...@cyberwind.net>
writes:

> Ken-
> I'm no authority on GMC MH carbs, but was under the impressions that
>
> there were two different carbs used on the TZEs.
> One was a Rochester and I'm not sure what the other was. I've
> heard i
> referred to as a GMC carb. I know that Dick took one look at my
> carb as
> said, "that's a good one."
> Please excuse me if I mislead anyone.
> Jim "Doc" White
> Wintergreen, VA
> 75 GMC Stretch (with Dick Paterson carb of some origin)
>

Check the GMC MI Parts Interchange list. There were many carbs, all I'D'd
by number.

David Lee Greenberg
Port St Lucie, FL
Dedicated to the Preservation of the Classic GMC Motorhome
http://GMCmhRegistry.com
48 Packard Super Eight
____________________________________________________________
Cheap Diet Help Tips. Click here.
http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTMerrX4LISyf7qTeKAhBlJF90IAy27W9DhybWGn3aOtmfnsgorq0Y/

[Emery Stora]

On Sep 25, 2009, at 6:51 AM, Jim White wrote:

> Ken-
> I'm no authority on GMC MH carbs, but was under the impressions that
> there were two different carbs used on the TZEs.
> One was a Rochester and I'm not sure what the other was. I've
> heard i
> referred to as a GMC carb. I know that Dick took one look at my
> carb as
> said, "that's a good one."
> Please excuse me if I mislead anyone.
> Jim "Doc" White
> Wintergreen, VA
> 75 GMC Stretch (with Dick Paterson carb of some origin)

Jim - I am pretty sure that they were all Rochester Quadrajets.
GM used seven different carbs for the GMC motorhome. 73 and 74 years
had a carb #7043254
75 and 76 and early 77 had 7045254 except for California emision carbs
which were 7045554
77 coaches with the 403 engine had 17057254 and California 17057559
78 had 17058254 and California 1758559

These carb numbers can be found on the left side of the carb, stamped
on the flat surface close to the secondary throttle shaft.

There is also a date code (4 digits) stamped in the same area. 73 to
76 coachs had a number starting with 70
77 & 78 carbs start with 170.
Some parts for these carbs are quite different on the 170 from the
70. DO NOT INTERCHANGE parts between these two series.

One example is the primary metering rods. They are .080" shorter in
the 170 series, they had a different taper to the rods and these carbs
used different sizes of primary jets.
The rods for the 70 series carbs will be stamped D-50. (7046338) I am
told that this was used ONLY in the GMC motorhome carbs. The 170
series are different. All GMC carbs used the same secondary metering
rods. These will be stamped with a CJ. The primary jets for the GMC
at your elevation should be .070". (7031970)

The proper power spring for the GMC is #7036019 which has an operating
range from 4" to 8" of vacuum.

One problem that some people have had is the use of gaskets from an
unknown kit. There are changes in the air passages in the carbs and
it is easy to install a gasket that covers an air passage hole and
that will make the carb perform improperly.

The Delco overhaul kit for the 73-74 is 7046812. For the 75-76 (non
Calif) it is 17051886

Emery Stora
77 Kingsley
Santa Fe, NM

[Wayne Barratt]

I had Quadrajet carbs on alot of my GM cars for the past 30 years and became rather adept at tuning them with good results.
However, even despite regular maintenance they would malfunction once in a while, dirt would stick the inlet needle open and cause flooding,the plastic cam that raises the secondary needles broke,and the float hung up on the plastic splash sheild (more flooding and a no start).

When I bought my 350 TBI Buick wagon, I was a bit worried about reliability , but in the 15 years I have owned it (over 300,000 kms) I have never had a single problem with the TBI or any of the sensors and computer that operates it.I have replaced the O2 sensor and fuel pump (routine maintenance) but the rest is as GM made it.

My motorhome has the Howell TBI setup and I am pleased with the way it performs, as others have said she starts instantly and it has never flooded,backfired, (or vapour locked to the point it wouldnt run).

I know others have experienced problems with the Howell TBI, but so far mine is fine.

A good quadrajet will get the job done (as they have for over 30 years), but If you are able to afford it, I would recomend the Howell TBI.
--
1976 23' GMCII By Explorer

[Gordon]

Gary;
I find some of those recommendations are very scary. Having seen people
implementing #4 & #5 and the destruction of mufflers, air cleaners and
resultant fires, I wouldn't reprint this information.
Gordon

Gary Casey wrote:
>
> I'd forgotten all about dieseling until I brought my "new" '73 home. Here are some of the tricks the experts at GM used to recommend:
>
> 1. Make sure the idle speed is as low as possible. Idea is to get the engine to stop turning before it has a chance to diesel
> 2. Shut the engine off under load. I always shut mine off in gear. Same idea - the extra load lowers the idle speed and slows the engine faster. If you could get the AC compressor to engage that would help, too.
> 3. Rev the engine up and the turn off the key. This is the opposite approach - get enough cool air to flow through and cool off the hot spots before the engine slows down to "dieseling speed.".

> 5. Add an anti-dieseling solenoid. This added air below the throttle to lean out the mixture.

[Shan Rose]

if you have dieseling, you need to adjust the timing some to get it to stop, or use at least 87 octane (piss gas) I know some parts of the country they even sell less hen 87 though its hard to imagine for me putting fuel in with this insanely low octane...

Gary Casey wrote on Fri, 25 September 2009 08&#58;35

[Ken Henderson]

Jim,

There are at least 8 different carburetors according to the GMC parts book
(7047354, 7047554, 7047555, 7045554, 17055154, 17055155, 17058254,
17058559). Those include versions for 455 ci & 403 ci, CA & non-CA for
each, and others that I have no idea why. All are Rochester Quadrajets,
AFAIK.

Ken H.

-----Original Message-----
Ken-
I'm no authority on GMC MH carbs, but was under the impressions that there
were two different carbs used on the TZEs.
One was a Rochester and I'm not sure what the other was. I've heard i
referred to as a GMC carb. I know that Dick took one look at my carb as
said, "that's a good one."
Please excuse me if I mislead anyone.
Jim "Doc" White

_______________________________________________

[fred veenschoten]

[quote

There is also a date code (4 digits) stamped in the same area. 73 to
76 coachs had a number starting with 70
77 & 78 carbs start with 170.
Some parts for these carbs are quite different on the 170 from the
70. DO NOT INTERCHANGE parts between these two series.

One example is the primary metering rods. They are .080" shorter in
the 170 series, they had a different taper to the rods and these carbs
used different sizes of primary jets.
The rods for the 70 series carbs will be stamped D-50. (7046338) I am
told that this was used ONLY in the GMC motorhome carbs. The 170
series are different. All GMC carbs used the same secondary metering
rods. These will be stamped with a CJ. The primary jets for the GMC
at your elevation should be .070". (7031970)

The proper power spring for the GMC is #7036019 which has an operating
range from 4" to 8" of vacuum.

One problem that some people have had is the use of gaskets from an
unknown kit. There are changes in the air passages in the carbs and
it is easy to install a gasket that covers an air passage hole and
that will make the carb perform improperly.

The Delco overhaul kit for the 73-74 is 7046812. For the 75-76 (non
Calif) it is 17051886

Emery Stora
77 Kingsley
Santa Fe, NM

[/quote]
thanks Emery. i have not seen this info before. i have a Cal. carb and it didn't have the rod and jet numbers i had seen. i bought the ones recommended but may have made a mistake in doing that. i'll check the numbers again. i' getting poor gas millage.

--
Fred V
'77 Royale RB 455
P'cola, Fl

[dennis...@aol.com]

Fred,

Here is a link to Frank Condos presentation on the quadrajet on the GMCWS site. Towards the end he explains the rod/jet combinations for the various carbs.

May be of help.

http://www.gmcws.org/Tech/quadrajet/index_files/frame.htm

Dennis Sexton
73 GMC
Germantown, TN
USA

-----Original Message-----
From: fred veenschoten <fred...@cox.net>
To: gmc...@temp.gmcnet.org
Sent: Fri, Sep 25, 2009 11:59 am
Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

[Ray Erspamer]

Not sure what format this link is in, but I can't get it to open worth a darn, parts of pictures scattered all over the page, makes no sense.

Ray & Lisa Erspamer
78 Royale Center Kitchen
The Malosco Cruiser (TZE368V101144)
Wauwatosa, Wisconsin 53226
Email: 78GMC-...@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/

________________________________
From: "dennis...@aol.com" <dennis...@aol.com>
To: gmc...@temp.gmcnet.org
Sent: Friday, September 25, 2009 12:21:55 PM

[Mr.erf ERFisher]

you need to use Internet Explorer , firefox does not seem to work

gene

--

Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Mr.erf ERFisher]

nah, the big problem was the leaking plugs on the bottom of the carb, the
stuck choke , and just crappy carb problems

gene

--

Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Bob Stockholm]

[quote title=Ray Erspamer wrote on Fri, 25 September 2009 13:51]Not sure what format this link is in, but I can't get it to open worth a darn, parts of pictures scattered all over the page, makes no sense.
<SNIP>

Works great for me but I am using Internet Explorer.

--
Bob & Terry Stockholm
Xenia, OH
1976 PB

[mills]

I tried FireFox and SeaMonkey. the page did not display correctly on
either, although slightly better with SeaMonkey. Since IE will not run
on my computers I guess I won't be able to look at the presentation.
Must be a MicroSoft thing.
--
Jim Mills
Greeley, CO
1973 CanyonLands 260 TZE-063V100731(under renovation)
1973 Glacier 230 TZE-033V101993

[Ray Erspamer]

Weird, works perfect in Explorer and goes bonkers in Firefox.....

Ray & Lisa Erspamer
78 Royale Center Kitchen
The Malosco Cruiser (TZE368V101144)
Wauwatosa, Wisconsin 53226
Email: 78GMC-...@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/

________________________________
From: Bob Stockholm <rstoc...@woh.rr.com>
To: gmc...@temp.gmcnet.org
Sent: Friday, September 25, 2009 1:07:11 PM

Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

[quote title=Ray Erspamer wrote on Fri, 25 September 2009 13:51]Not sure what format this link is in, but I can't get it to open worth a darn, parts of pictures scattered all over the page, makes no sense.

[Gary Casey]

Gordon,
You're probably right - it could happen.  Some of the cylinders would pass enough unburned fuel to fill the exhaust system and then the culprit cylinder lights it off.  The only foolproof way was to have a manual transmission.  With those I just killed the engine dead.  Then shut it off.  Using higher octane fuel will inhibit the autoignition that causes it, but that costs money (:-(.  I don't see how changing the ignition timing would help, since the ignition is off during dieseling.  A more advanced timing does make the surface run slightly hotter, so I suppose that could lead to dieseling (we called it "afterrunning").
Gary

________________________________
From: Gordon <wiz...@telus.net>
To: gmc...@temp.gmcnet.org
Sent: Friday, September 25, 2009 8:35:03 AM
Subject: Re: [GMCnet] dieseling

[mills]

Probably written with a MicroSoft composer. MS has a history of trying
to lock in the market rather than adhere to industry standards.

--
Jim Mills
Greeley, CO
1973 CanyonLands 260 TZE-063V100731(under renovation)
1973 Glacier 230 TZE-033V101993

On Fri, 2009-09-25 at 11:45 -0700, Ray Erspamer wrote:
> Weird, works perfect in Explorer and goes bonkers in Firefox.....
>
> Ray & Lisa Erspamer
> 78 Royale Center Kitchen
> The Malosco Cruiser (TZE368V101144)
> Wauwatosa, Wisconsin 53226
> Email: 78GMC-...@att.net
> 414-745-3188
> Web Site: http://ray-lisa.page.tl/
>
>
>
>
> ________________________________
> From: Bob Stockholm <rstoc...@woh.rr.com>
> To: gmc...@temp.gmcnet.org
> Sent: Friday, September 25, 2009 1:07:11 PM
> Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI
>
>
>
> [quote title=Ray Erspamer wrote on Fri, 25 September 2009 13:51]Not sure what format this link is in, but I can't get it to open worth a darn, parts of pictures scattered all over the page, makes no sense.
> <SNIP>
>
> Works great for me but I am using Internet Explorer.
>
>

_______________________________________________

[fred veenschoten]

Dennis Sexton wrote on Fri, 25 September 2009 12&#58;21

> Fred,
>
> Here is a link to Frank Condos presentation on the quadrajet on the GMCWS site. Towards the end he explains the rod/jet combinations for the various carbs.
>
> May be of help.
>
> http://www.gmcws.org/Tech/quadrajet/index_files/frame.htm
>
> Dennis Sexton
> 73 GMC
> Germantown, TN
> USA

thanks Dennis. i finally got it working with IE.

i believe this is what i used to select the 50D rods and #70 jets when i rebuilt my carb. i need to check the date # Emery suggested. i may have messed up by changing the rods. i still have the old ones.

[Chris Choffat]

The EM-50 Dieseled in Stripes at the Czech Check point. :d

--
-Chr$
77 Kingsley 455 Under painstakingly long Rennovation
Scottsdale, AZ

[Jim Kanomata]

Patterson understands what our motor home requires.
He will not throw in some parts to finish the job.
Our results have always been great.
We can earn more margin by having the local shop do the carbs. We
rather have our customers get the results that they hear from their
fellow GMC.

On Thu, Sep 24, 2009 at 3:31 PM, MICHAEL FOSTER <mfost...@yahoo.com> wrote:
>
>
> A reputable shop here wants to charge $195 to rebuild my QUADRAJET when I bring it in to them.  This includes new shaft & bushings, setting up carb/ fuel level, accelerator pump etc.,
>
> Looks like a Dick Patterson rebuilt carb costs about $390 plus shipping charges from our GMC suppliers.
>
> TBI (throttle body injection) Howell can be purchased (but not installed) for about $1100.00
>
> Any differing opinions about the value of each?  Where best to spend money.
>
> Michael

> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Rob Allen]

Mr ERFisher wrote on Fri, 25 September 2009 10&#58;59

> you need to use Internet Explorer , firefox does not seem to work
>
> gene
>
>
> On Fri, Sep 25, 2009 at 10:51 AM, Ray Erspamer <78gmc-...@att.net> wrote:
>
> > Not sure what format this link is in, but I can't get it to open worth a
> > darn, parts of pictures scattered all over the page, makes no sense.
> >
> > Ray & Lisa Erspamer
> > 78 Royale Center Kitchen
> > The Malosco Cruiser (TZE368V101144)
> > Wauwatosa, Wisconsin 53226

For what it is worth, it opens just fine with Apple's Safari browser, so I can't blame it on Microsoft for a change...LOL.

--
Rob Allen
'76 x-PB

[Rick Denney]

Chris Choffat writes...

> The EM-50 Dieseled in Stripes at the Czech Check point. :d

I guarantee that the sound of that engine being shut down was not
recorded on location that day. Nearly everything we hear in a movie is
added after the shoot. I'm sure something dieseled, and maybe it was
the GMC, but lots of movies used similar recorded sounds because that
was the way cars ran in those days when they were not properly
maintained.

The Rochester has maintenance requirements, probably much greater than
TBI, but still not onerous since we have such a good expert in our
midst. My coach does not and has never dieseled.

Rick "whose 1970 Cutlass had a two-barrel carb with an anti-dieseling
solenoid on it" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

[Rick Denney]

Mr.erf ERFisher writes...

> here were my reasons for upgrade to a TBI

You just had to know that this would generate a response. Here's my
late hit.

> *MY REASONS FOR UPGRADE*

> 20 Year upgrade in technology

Yes, but it's not a complete upgrade. The engine wasn't designed for
it and everything is a compromise in the way the sensors are arranged,
the lack of spark control, and so on.

> No more dieseling at shut down or slapping the gas 10 times to start

Huh? Mine NEVER diesels. Ever. And I turn the key on, press the gas
pedal twice like the owner's manual says (which allows the automatic
choke to set itself properly), and start the engine. (I do have an
electric fuel pump).

> No more sticking choke and other linkage

Mine doesn't stick. That does require a squirt of Kroil once in a
while, which I do the once or twice a season when I remove the air
cleaner to vacuum up the mouse nests.

> Get rid of the Carb input filter connection

I got rid of that without getting rid of the carb.

> No more leaking / varnished linkage, floats, jets, set screws, etc

Sending the carb to Dick for renewal every few years will maintin
excellent operation without any of these issues, and will still be one
of the cheapest long-term maintenance operations on a GMC.

> Closed loop control of combustion for altitude, gas, engine
> condition, etc

The altitude thing is the compelling argument. But the ECM will run
open-loop much of the time, and the oxygen sensor's position is
variable across installations and therefore requires some fine-tuning
of the look-up tables. Plus it's still one oxygen sensor (which
measures only one bank) and one injector site, so any variability in
the mixture quality caused by the intake runners, etc., will not be
compensated. TBI can run one or two cylinders lean because of that, if
the tuning isn't adjusted for that possibility. It has happened.

> Module swap repair of system, i.e. , injectors, computers, sensors,
> etc

Bet it's easier to make a carb work on the side of the road than an
injection system.

> Electronic diagnostics

Sort-of--and then only for real techies.

> No new Quadrajet carburetors available, no upgrade possible with old
> system

Yes, this is a compelling argument, eventually.

> Technology proven in all modern engines since about 1986

No on the "since 1986" part. The throttle-body injection system was
used for a fairly brief period in the 80's and early 90's, and was
replaced pretty quickly by port injection systems and much more
extensive computer control and remote sensing.

> must say, I was very embarrassed when ever I came to a stop in a campground
> and the GMC would diesel on for several minutes then backfire with a big
> black cloud of smoke out the back (also ruined 2 muffler sets).

Any approach can deliver poor results if not properly executed. As I
said, my coach does not diesel and has never backfired when the timing
was correctly set (which is, by the way, also required for the TBI
system). And I get the same 8-10 mpg that you do, and can drive away
as soon as my suspension system is aired up.

What about the surge issue that many have reported with the Howell
system, where there is a hesitation on startup from a stop? What about
people who may have silicone gasket sealants on their engine and not
know it (the silicone will ruin the oxygen sensor)? I sure do hear a
lot of talk about trading this and that ECM programming chips, and
talk of finding old PROM burners, etc., so people can roll their own
lookup tables for open-loop operation. I hear about people driving
around with a laptop on the passenger seat, and so on.

Sounds like a fun hobby, and that's a good enough reason for the
switch. But for those unwilling to dig into it at that level, a
properly and routinely rebuilt original carb results in excellent
general operation. A time will come when all the cores are ruined, or
Dick gets tired of it and is no longer available to us, and at that
time we may all have to switch to TBI to keep the coaches going. But
for those who have an original carb, keeping it maintained is still a
completely viable option.

Rick "who occasionally likes to twist Gene's tail" Denney

[Mr.erf ERFisher]

Cool that you live in Nirvana, not like the real world

JWID
gene

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Rick Denney]

Gary Casey writes...

> I'd forgotten all about dieseling until I brought my "new" '73
> home.  Here are some of the tricks the experts at GM used to recommend:

Proper shut-down requires a well-maintained carb, correct timing,
correct idle speed, and the recommended fuel.

Rick "whose coach does not diesel on shut-down" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

_______________________________________________

[CYNTHIA R LOGUE FOR TOM LOGUE]

Rick,
I ditto that.

Tom Logue
73 Glaicer
Grand Junction, CO 81504

[Gordon]

Rick;
Did you read of Bruce's success as soon as he switched to an intelligent
ECM? Dynamic EBL. HOWELL is still 1980's technology and the
frustration of many says it all. He drove his coach to Howell and they
gave him some more useless bandaid solutions.
I think what Bruce has done is the most important step forward with EFI
that anyone has taken so far. Certainly the most PUBLIC step I have read.

Bruce wrote:

> I finally got it running good enough that I was confident in driving
the 2 plus hours to Howell so that Troy could look at it. I went to
Howell this morning and Troy made some major changes to the fuel tables.
It now works much better than before, not perfect, but hey, alot better
than the Carb did, very drivable.
>
The Dynammic EBL system has 8 banks so I programmed bank zero with the
BPC number it should use for a 455 engine and 80pph injectors. I also
did a second Bin with the same 154 BPC (BPW) number that Howell uses.
>
> I started the engine on the 134BPC and it started right up, but the
idle was not smooth so I clicked the 154Bin and wow! it started to idle
as smooth as a kitten! I read up on the VE learn function and started
that feature and went for a drive. It ran better and smoother on the
default values than the old ECM ever did. I stopped a couple of times
and updated the system with the new learned values and each time it ran
even better. Then I ran out of time :(
>
> The engine runs much smoother and quieter and ever before with lots
of torque! I am going to use this as my main ECM and keep the Howell as
a backup.
>
> It runs now the way I had expected it should run when I changed over
to EFI (touch wood). Troy at Howell has been great, but he is working
with the limitations of 1980's technology. The EBL system is much faster
and the VE table is much finer in RPM and MAP pressure splits.

[Rick Denney]

Gordon writes...

> I think what Bruce has done is the most important step forward with EFI
> that anyone has taken so far. Certainly the most PUBLIC step I have read.

No argument from me. There are always those who push the boundaries,
making things possible for the rest of us. They do it because it
interests them, and no other justification is required.

But that doesn't mean it's the right path for everyone. Everything
described about the process to achieve that success highlights how
different it is from putting the original carb in a box, shipping it
to Dick, waiting a week, getting it back, and bolting it to the top of
the engine with little further work required.

Rick "who already has enough hobbies" Denney

[Ken Henderson]

My EBL Flash came today. It will be a few days before I finish the HVAC and
get to trying the EFI.

Ken H.

-----Original Message-----
Rick;
Did you read of Bruce's success as soon as he switched to an intelligent

ECM? Dynamic EBL...

[Ken Henderson]

My EBL Flash came today. It will be a few days before I finish the HVAC and
get to trying the EFI.

Ken H.

-----Original Message-----
Rick;
Did you read of Bruce's success as soon as he switched to an intelligent

ECM? Dynamic EBL...

[Gordon]

Ken;
I look forward to your success. EFI was always on my long list, but too
many people have had too much trouble for me to jump on it before doing
my homework. I'm going to check back with my MegaSquirt guy and get his
latest advice. It seems that MegaSquirt has had great success if given
half a chance.

The one feature of EFI no one seems to stress is the life of the engine.
My friends in the auto wrecking business no longer count mileage for
much when guarantying an engine. They will guaranty any used EFI engine
that has oil pressure, for 24,000 miles. They tell me EFI engines will
always go 2-3X as far as a carburetted engine. Their experience tells
them that the very rich mixture, with a choke on, is very hard on
cylinder walls and pollutes/dilutes the oil. They find EFI engines that
have had reasonable oil and filter changes still have good compression
after 250-300,000 miles.
Were you the one who found the EBL to begin with?
Gordon

Ken Henderson wrote:
> My EBL Flash came today. It will be a few days before I finish the HVAC and
> get to trying the EFI.
>
> Ken H.

[Neil Martin]

So - do any of you fuel injection converts have a genuine rebuildable motorhome carb that a carb guy could buy? I need a Patterson rebuild but somewhere in the dark ages my coach got a different carb (model # 17054938) and I need a core.

Just wondering...

Thanks for your time.
--
Neil
76 Eleganza
Los Angeles

[Ken Henderson]

I've been aware of EBL for quite a while, but I wouldn't claim to be first
-- Bruce is the first I know to bite the bullet & buy one. I've been so
close to the decision that his first report prompted me to go ahead and
order. I'll probably install the kit in my spare ECM tomorrow.

Ken H.

-----Original Message-----
Ken;
I look forward to your success. EFI was always on my long list, but too
many people have had too much trouble for me to jump on it before doing my
homework. I'm going to check back with my MegaSquirt guy and get his latest
advice. It seems that MegaSquirt has had great success if given half a

chance...

[Ken Henderson]

Sorry, Neil, I can't help: I'm considering a Cad 500 swap, which will
receive the EFI, leaving the 455 needing the carb.

Mine wouldn't be a CA version anyway -- another problem imposed on you by
CA's EPAdiots.

Ken H.

-----Original Message-----
So - do any of you fuel injection converts have a genuine rebuildable
motorhome carb that a carb guy could buy? I need a Patterson rebuild but
somewhere in the dark ages my coach got a different carb (model # 17054938)
and I need a core.

Just wondering...

Thanks for your time.
--
Neil

_______________________________________________

[Neil Martin]

Thanks Ken.

I am totally unconcerned about it being a California Carb, so long as it is a motorhome carb. (I have never ever seen anyone check the carb number.)

Anybody out there...?

--
Neil
76 Eleganza
Los Angeles

[Don Tracy]

>
> Gordon writes...
>
>> I think what Bruce has done is the most important step forward with EFI
>> that anyone has taken so far. Certainly the most PUBLIC step I have
>> read.
>
> No argument from me. There are always those who push the boundaries,
> making things possible for the rest of us. They do it because it
> interests them, and no other justification is required.
>
> But that doesn't mean it's the right path for everyone. Everything
> described about the process to achieve that success highlights how
> different it is from putting the original carb in a box, shipping it
> to Dick, waiting a week, getting it back, and bolting it to the top of
> the engine with little further work required.
>
> Rick "who already has enough hobbies" Denney
>

To those who are on a rant about newest technology with ECM to control fuel
injection and spark (coil packs), should talk to either or both of the Jims
about my experience with the "latest technology" in engine control.

After spending over $5,000 in trying to make Leigh Harrison's system work
and then a greatly modified Harrison system, I'm now running Dick
Patterson's distributor and carburetor because my wife cut off my
experimental funds and Jim B recommended that I do it.

Bottom line, unless your GMC is a hobby and not a motorhome to travel cross
country, stay with proven technology. I can now leave home on a 5000 or 7500
mile trip without worrying where I will have problems that no one but a
highly skilled tech in Colonial Beach, VA can help me. With old and proven
technology, nearly any shade tree mechanic can get me back on the road.

I still think ECM controlled F/I and coil packs are intriguing ideas but not
for the 455.

Don
'76 Royale rebuilt by Jim B
Livingston, TX

[Larry Davick]

It comes down to

Carb + Distributor = 100 years of perfecting
EFI + coil packs = $5,000 of perfecting.

I think I get it now.

----- Original Message -----
From: "Don Tracy" <dtr...@livingston.net>
To: gmc...@temp.gmcnet.org
Sent: Monday, September 28, 2009 6:10:53 PM GMT -08:00 US/Canada Pacific
Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

>

[Larry Dilk]

________________________________
From: Gordon <wiz...@telus.net>
To: gmc...@temp.gmcnet.org
Sent: Monday, September 28, 2009 7:41:50 PM

Subject: Re: [GMCnet] Rebuilt carb, Dick Patterson carb OR TBI

Ken;

________________________________

To Any and All

Not anything but my experience, I have a previous owner installed Turbo City Fuel Injection and in the 3 years of ownership it performs like I bought it from GM in the 80s and it runs great with out tinkering.  I know the PO was not an EFI or computer guru by any stretch and he installed it himself. So not all of them are a problem.

Larry Dilk
76 Eleganza II, Patterson 461. TBI  Just Love It
 Indianapolis

[Gary Casey]

Okay, I'll bite - what is the difference between a "well-maintained" carb and a not-so well-maintained carb? Can I tell by looking? I assume not. I also assume that the things about the carb that affect after-running tendencies are idle air/fuel and speed adjustments, right? I suppose if the part-throttle mixture is too rich it might result in carbon build-up in the combustion chamber? Or?

The comment "correct timing" leads me to believe that timing either too advanced or too retarded will cause dieseling. I'm still learning here, but it looks like this engine comes equipped with a TVS that switches from full-vacuum spark to ported spark when warm. Some people disconnect this, giving much more advance at hot idle. Is the "correct" or "incorrect"? Who is it that decides what is "correct"? The shop manual? In that case the TVS would stay hooked up. Back in the olden days I recall that going to full vacuum reduced after-runnning because it caused one to close the throttle more at idle, reducing the fuel availability after the ignition was turned off. Same as the anti-dieseling solenoid. Since there is no (spark) ignition after it is turned off, ignition timing must have an indirect affect on after-running.

Same question about the "correct" idle speed and "recommended" fuel. Where is all this knowledge that we with "dieseling" engines seem to not have?

Thanks for the patience,
Gary

________________________________
From: Rick Denney <ri...@rickdenney.com>
To: Gary Casey <gmc...@temp.gmcnet.org>
Sent: Monday, September 28, 2009 1:55:42 PM
Subject: Re: [GMCnet] dieseling

[Rick Denney]

Off list.

Do you think Alan still won't need the 455 you are removing when you
install the Cad engine? You hinted that it might be possible for me to
come down and get that engine from you, and if you are still willing,
I'm in. Depending on whether my engine finds someone who can rebuild
it, the carb may still end up as surplus.

Best Regards,

Rick

Ken Henderson writes...

> Sorry, Neil, I can't help: I'm considering a Cad 500 swap, which will
> receive the EFI, leaving the 455 needing the carb.

'73 230 Ex-Glacier "Jaws"
Northern Virginia

_______________________________________________

[Rick Denney]

Rick Denney writes...

> Off list.

Sorry to all. That was intended to be private.

Rick "who does sometimes hate email" Denney

[Ken Henderson]

& just for spite, I'm not gonna tell y'all what I answered. Eat your hearts
out. :-)

Ken H.

-----Original Message-----
Rick Denney writes...

> Off list.

Sorry to all. That was intended to be private.

Rick "who does sometimes hate email" Denney

_______________________________________________

[Ken Henderson]

& just for spite, I'm not gonna tell y'all what I answered. Eat your hearts
out. :-)

Ken H.

-----Original Message-----
Rick Denney writes...

> Off list.

Sorry to all. That was intended to be private.

Rick "who does sometimes hate email" Denney

_______________________________________________

[Rick Denney]

Larry Dilk writes...

> Not anything but my experience, I have a previous owner installed
> Turbo City Fuel Injection and in the 3 years of ownership it
> performs like I bought it from GM in the 80s and it runs great with
> out tinkering.  I know the PO was not an EFI or computer guru by any
> stretch and he installed it himself. So not all of them are a problem.

Larry, you are right. Sometimes--probably most of the time--everything
works and just keeps working. Sometimes, things go wrong. With
fuel-injection kits, when they go wrong, they sometimes go
park-by-the-side-of-the-road wrong.

And there is EFI and EFI. The Howell kit and many of the roll-your-own
kits using standard GM parts are throttle-body injection, not port
injection. Port injection is MUCH more difficult to tune properly by
any measure. The throttle-body injection uses a relatively simple ECM,
and the chip on it uses relatively simple programming. There are
cadres of TBI-equipped Camaro (etc.) hot-rodders who have kept that
technology alive and who provide an extensive knowledge base for the
information going into the chip, and for the equipment needed to burn
those chips.

Many have installed the Howell kit and receive good service from it.
It's probably true that most who have done so were on the end of the
spectrum of GMC owners that enjoys delving into experimental
approaches and making them work. For those willing to follow in those
footsteps, a good first place to start is Richard Waters's slide show
on the Howell kit, and then Ray Swartzendruber's article on the
Gengeral Motors throttle-body injection using factory parts. Both of
these articles are at: http://www.gmceast.com/technical/

I am in no way opposed to installing fuel injection, and have
considered doing so myself based on the success some others have had.
But then I see where such experts as Ken Henderson are still devoting
life-minutes to getting his to work the way he really wants it to work
(which may go far beyond what would make the rest of us happy), and
that gives me pause. That, and the $1100-plus, and the continued good
service I get from a Paterson-rebuilt carb.

Making the modification such that all the parts are used within their
application envelope, replaceable and repairable in the field, and not
so obscure as to prevent proper diagnostics when things go wrong is
the big challenge.

And we should remember that these engines were never run with fuel
injection. The carbs were designed to run a bit rich to account for
two things: 1.) Rochester's production tolerances, and 2.) variations
in flow and mixture control through the intake runners, cylinder-head
intake ports, and intake valves. According to GM engineers in our
midst, Rochester's tolerance for producing a given mixture was 6%, so
they made them run 6% rich. Running a little rich was far better than
running a little lean, which causes high combustion-chamber
temperatures and resulting damage.

Fuel injection eliminates the variation in mixtures control by the
carb, but it does not eliminate the variation in mixture control in
the intake passages. So, we still need to run it a bit rich.

Many of the fuel injection systems are programmed to provide the
stoichometric 14:1 air/fuel ratio. This is not what GM intended with
their systems. They intended the injection system to run a little rich
during demand for high power, and a little lean when the throttle is
mostly closed. The reason is that during power demand, their intent is
to provide an abundance of fuel so that all the air gets used up. This
maximizes power. And during part-throttle cruise, their intent is to
provide an abundance of air so that all the fuel gets used up. This
maximizes economy. The limits of these are when combustion fails
because the mixture is to extreme, or when the engine no longer meets
emissions standards. The carb does this using the power valve and the
power entrichment circuit, and fuel injection does it, too, based on
the throttle-position sensor.

All these kits use a single oxygen sensor, mounted on one bank of the
exhaust system. Thus, it measure fuel mixture for half the engine, and
then an average of all the cylinders on that bank. For closed-loop
operation (where the injection system is adjusting the mixture based
on what it sees in the exhaust), it is still possible for one cylinder
or two to be lean while the others are a little rich. So, it still has
to be adjusted slightly rich to prevent running a cylinder too lean.
Port injection minimizes this problem by controlling mixture
separately for each cylinder.

The problem with carbs is that too many of them are not running
properly, mostly because of low-grade rebuilds and replacements, or
lack of maintenance. Tuning a carb is more than just getting the
engine to run well in the driveway, of course. GM tested carbs in a
wide range of situations to provide acceptable operation, and getting
that versatility requires being faithful to GM's carb tuning design,
with maybe a few careful responses to changing fuel formulations. The
big advantage to fuel injection is that it does not degrade over time
the way carbs do, so those who elect to use carbs should be committed
to good and proper maintenance to achieve what Gene calls "nirvana".
Or, we can put that energy into the system up front when installing
and tuning a fuel injection system. Making an old engine run well
requires that care at some point in the process.

Rick "wary of fuel system evangelists" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

_______________________________________________

[Rick Denney]

Gary Casey writes...

> Okay, I'll bite - what is the difference between a
> "well-maintained" carb and a not-so well-maintained carb?

I didn't know the history of my carb when I bought my coach, and I had
problems such as a dirty float valve and some driveability issues, so
I assumed (correctly) that it was not properly maintainied. After
installing a Paterson-rebuilt carb, the driveability, economy, and
power of my coach improved remarkably. Now, the challenge is keeping
it there. I figure once every five or eight years, or if I notice any
symptoms, I'll box it up and send it back to Dick for a fresh rebuild.

The best check, it seems to me, is the appearance of the spark plugs
during routine maintenance. For every tune-up, the plugs should be
removed and inspected. A clean plug with a tan grounding electrode
represents a good mixture in use. A plug with black fluffy-looking
deposits represents excessive richness, and a plug that is white
represents excessive leanness. Black wet deposits indicate oil
fouling. Extended idling can affect plug appearance, so I check mine
after a run (and after the engine cools).

> I also assume that the things about
> the carb that affect after-running tendencies are idle air/fuel and
> speed adjustments, right?

I would suspect that too lean an operation will cause excessive
combustion chamber heat which can cause dieseling (as the edges are
hot enough to ignite fuel without help from the ignition system), or
even that too rich an operation can create more carbon buildup that
can also glow hot enough to ignite fuel without benefit of ignition.

> The comment "correct timing" leads me to believe that timing either
> too advanced or too retarded will cause dieseling. I'm still
> learning here, but it looks like this engine comes equipped with a
> TVS that switches from full-vacuum spark to ported spark when warm.

The TVS advances the engine at idle when it is very hot to increase
the idle speed and to make the engine run cooler, and retards the
timing when it's not too hot to reduce emissions. It does this by
switching the vacuum advance source from ported to manifold vacuum
when the engine is hot. That is all it does.

My issue with timing is that if the timing is off, the combustion
chambers can run hotter than they should, and I think that can
contribute to dieseling. (New thought: Plugged mufflers might also
contribute to the problem.)

> Some people disconnect this, giving much more advance at hot idle.

Actually, it gives the same advance at hot idle, but more advance at
cool idle, when one uses manifold vacuum to power the vacuum advance.
This is a religious topic, and has caused as much argument on this
forum as anything except tires, despite that we had the clarity of GM
engineers who were responsible for these designs back in the day
illuminating the topic. I won't feed that, except to say that I don't
have a TVS and I use manifold vacuum for advance, and I don't have
dieseling. I don't know if one affects the other; I've never tested
it.

> Back in the olden days I recall that going to full vacuum
> reduced after-runnning because it caused one to close the throttle
> more at idle, reducing the fuel availability after the ignition was
> turned off. Same as the anti-dieseling solenoid. Since there is no
> (spark) ignition after it is turned off, ignition timing must have
> an indirect affect on after-running.

Sounds reasonable to me.

> Same question about the "correct" idle speed and "recommended"
> fuel. Where is all this knowledge that we with "dieseling" engines seem to not have?

My idle speed is about 600 or 650, and about 500 or a bit higher when
in gear, adjusted after setting the timing and idle mixture. I use
regular-grade fuel (87 octane as it is measured these days). My timing
is 10 degrees BTDC following the procedure in the maintenance manual
explicitly (including disconnecting and blocking the vacuum advance
and running the engine at 1100 RPMs). I adjust the idle mixture by
turning it in until the engine starts missing and then backing it out.
I meticulously maintain my vacuum hoses, which seem to require it.

It is possible, I suppose, that my use of an electric fuel pump in
lieu of a mechanical pump is helping to prevent the problem, though it
seems to me that if the carb bowl has fuel in it it wouldn't matter.
But I mention it just in case it sparks an idea.

Rick "not thinking this is all that mysterious" Denney

[Gary Casey]

I have to mostly agree with Rick, but partly disagree. I'm also "in no way opposed", but for now I'm not going to go to EFI, and I even have a V8 distributorless spark and sequential multipoint system that I previously ran on a 928 sitting but not sitting in a box (the system, not the car. Well, the car is, too - different story). I designed and built it myself, so the calibration is "no problem." Yeah, right.

True, the engines "were never run with EFI" but there is nothing about the engine that prevents it from running very well on EFI. The Seville 350 is basically the same engine with a narrowing intake manifold(lower deck height) and it ran very fine, thank you. I would like to disagree with Rick's 6% number, but that's probably about right, and it might be worse. When we were doing carburetors and single point systems (I was there then) and got within 1.5 air/fuel ratios from leanest to richest cylinders we thought we were doing well (that's 10% range, or +/- 5%). It was usually better than that, but not always. The Oldsmobile V8 with the Q-jet was one of the better engines at part throttle. The Small-block Chevy was certainly the worst. Olds pushed the middle intake ports outboard to give more room for the runners and that, along with the shallower valve angles, gave more room to get the fuel balanced - but made for a wider, heavier engine. The
Q-jet has very good fuel delivery at part throttle, probably the best in the business, but at full throttle it is pretty bad. Maybe really bad. All kinds of fixes were implemented, including premature WOT stops on the secondary throttles, various shaped baffles on the air valves, etc. To get good WOT distribution a Holley with equal-size bores was the way to go. Unfortunately, our vehicles spend more time at WOT than the Toro. I usually go WOT only when other methods of getting up the hill fail - like taking a run for it and then downshifting. I'm tempted to put a light on the dash to tell me when the secondary throttles open - that probably increases the BSFC by 10%.

True, multipoint EFI systems still live with the air variation in the manifold, but the standard Oldsmobile manifold is pretty good in that regard. And there is no reason to "run rich", as some cylinders can run acceptably a little lean of the target. Contrary to apparently common belief, the engine calibrators back then didn't set the engines to "run rich", but they set them at close to best economy at part throttle. True best economy operation would usually result in a little surge due to time-varying fuel delivery(you should put a glass top on an intake manifold - I did. You would be horrified at what you see). That is a little leaner than stoichiometric (stoic is about 14.7). And as far as I know ALL early EFI systems were stoic systems running with a narrow-range O2 sensor. They ran well within 1% of stoic, probably 0.1% most of the time. This is richer than best economy, but in a rare happy coincidence, if just less than 10% EGR is added,
stoic becomes the best economy mixture. Lots of people disconnected their EGR thinking they were doing a good thing, but it just made fuel economy worse. I digress - I don't think any of our engines have EGR anyway.

Yes, putting an O2 sensor on just one bank isn't the perfect answer, but since we're not running a 3-way catalyst I see no problem with it at all. Could put it at the "Y", but it would take a lot longer to warm up and the response would be slower.

One of the big advantages of EFI is that the system can have the smarts to stay lean at nearly full throttle. The Q-jet and most other carbs use a full throttle enrichment operated by vacuum. When manifold vacuum drops to maybe 5 inches, the valve opens by lifting the needles and it goes rich. Good for driveability, but bad if you want best economy as close to WOT as possible. EFI systems can be programmed to maintain a stoic mixture even at WOT, and many did - the mixture wasn't enriched until higher rpms were reached. To me, that's one of the biggest problems with the Q-jet in our applications - the engine is running at low rpm, but high load and keeping out of the power enrichment is not easy. On mine I'm tempted to tweak the shift points to get the transmission to keep the engine at higher rpm (oops, drifting into a torque converter discussion...). To a great extent, we "drive" the carburetor and torque converter - nothing else matters much.
The engine just connects the two.

Note that TBI doesn't address many of the issues with carburetion. It still suffers from the same fuel distribution problems of the carburetor. The only reason we went with TBI at the OEM's was that it provided a way to closed loop operation more effectively than a closed loop carburetor. It was never even proposed as a way to improve engine operation itself. I developed the first experimental closed loop Q-jet and we used a vacuum modulator on the power enrichment. Worked after a fashion; good enough to meet the emissions target.

Some time back, someone opined that EFI makes engines last longer - several times longer. Well, it certainly helped, partly because of the reduced time spent rich and partly because fuel distribution was better, but that ignores the thousands of other improvements that are mostly responsible for today's engines longevity.

Bottom line? I'm afraid the effort to change to TBI isn't worth it. I wouldn't go to EFI unless it was a multipoint system. Just my opinion, FWIW.

Gary "not an evangelist" Casey

....

I am in no way opposed to installing fuel injection, and have
considered doing so myself based on the success some others have had.

....

All these kits use a single oxygen sensor, mounted on one bank of the
exhaust system.

....

The problem with carbs is that too many of them are not running
properly, mostly because of low-grade rebuilds and replacements, or
lack of maintenance. Tuning a carb is more than just getting the
engine to run well in the driveway, of course.

....

Or, we can put that energy into the system up front when installing
and tuning a fuel injection system. Making an old engine run well
requires that care at some point in the process.

Rick "wary of fuel system evangelists" Denney

[Chuck Kellogg]

This is just another comment on Dick Patterson's products. I got his carb,dist & wires at the BerrinSprings rally. Colorado
springs to Michigan I ran a little over 8 MPG after Dicks works returned to Colorado at n adv. of 12 MPG, I whish I done this eariler. Just another two cents added. Chuck Kellogg 76 exPalmBeach
--
Chuck Kellogg
1976 Ex Palm Beach
Colorado Springs, CO