[GMCnet] Differences between motorhome and car engines?

[Darryl Meyers]

OK, I've pretty much made the decision to replace my engine with a "remanufactured" engine. I'll get on the phone Monday to S&J and maybe Motorworks (Thanks Karen and Jerry for your comments). If anyone has any other rebuilders they have had a good experience with I'd like to hear from you.

What is different about the 403/455 engines we use in the motorhome and the same engines in the Toronado and other automotive applications? I understand the cam is different; what is the difference? Anything else? What do I need to ask for to make sure the engine is set up properly for the motorhome?
--
Darryl Meyers

1978 Eleganza II

El Dorado Hills, CA
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[mike foster]

There is no substitute for cubic inch displacement. All other things being equal a 455 should make it torque peak approximately 12% lower in the rpm than the 403. So, if the 403 toque peaks at 2600 the 455 should peak around 2300. How many rpm does the 455 turn at 60 mph with the stock differential ratio? Low rpm stump pulling torque is what the GMC needs.

Whatever you do, pop for the Crane Roller cam/lifter kit and forget about flat tappet cam problems with 'modern' oil. Roller rockers wouldn't hurt either. Erson forged units have a rounded edge on the push rod side (they did for a SBF) and this allows you to dimple the splash guard where the rocker hits so it will then clear and can fit under a stock height SBF rocker box, never tried it on the Olds, but I took enough money from guys who didn't think you could put full roller rockers under the cover without spacing it or going to tall covers to more than pay for them.

I would also check into a gear drive for the cam. They make them for Fords and Chevys with helical cut gears that don't scream at you. Not sure about Olds at this time.

[Chris Tyler]

Agree 455 or more CI - torque is where its at.

Roller cam is better if you can afford it. Not cheap.

Cam should have peak torque close to your cruising RPM. Crane likes wider LSA ~114, Comp likes narrower ~110

Roller rockers may not hold up all that well depending on the brand. If you do run them, you will likely need to space the cover up [2 extra gaskets coated and glued worked on my buddys olds jet boat] cut and reweld your covers or expensive tall covers.

Gotta disagree with the gear drive. A quality double roller chain is fine.

All this is moot for production rebuilds as they usually run what they run. You'll have to ask if they will do custom mods and if it will effect their warrantee.


--
76 Glenbrook

[dwayne jacobson]

Worth to contact jim hupy on a rebuild

dwayne j

[KB]

I would have liked to switch to a 403 (for better mpg's) when we did our replacement, but it was going to be too hard to find all the other stuff (tinwork, manifold, brackets) so we stuck with a 455.

I'd also have loved to go to roller lifters and roller rockers, but the price difference was too much for us (almost doubled the cost). At that point, I'd seriously consider one of JimB's engines instead.

If you talk to S&J and tell them it's for a GMC Motorhome, it'll basically be their heavy truck engine build (Note: the warranty on their heavy vehicle engines is only 12 months, not 5 years like on their car engines).

At a minimum, add a double row roller timing chain; the cost is small (eg Cloyes tru roller or Melling 40409). One of the best GMC engine builders told me privately that oil restrictors are not needed on a hydraulic lifter engine, but strongly suggested a high volume oil pump and pickup (eg Melling EM22FHV and D22FSI). We also went with an RV cam (eg Melling MTO-1, Elgin E-976P, or equivalent), but that's not technically legal on a CA coach that must pass smog tests. I believe Jerry Work went with a standard cam but advanced it 4 degrees.

Sorry, these part numbers are for a 455; I don't know what the 403 equivalents would be.

Hope this helps.


Karen
1973 23'
1975 26'

[John R. Lebetski]

The Qjet part numbers are MH specific. So is the distributor curve. If Jim K is not doing engines as another thread mentioned, you could call Cinnabar for a price. That would give you a price you could try to be under for reference. They use an 'RV' type cam, oil restrictors and exhaust crossover restrictors so the choke still works. I think the warranty was 18 mos unlimited mileage. I have one as I needed the replacement while in Mi. No problems though I did advance the timing from where they set it it was a real dog and gas hog running too retarded.
--
John Lebetski
Chicago, IL
77 Eleganza II
Source America First

[John R. Lebetski]

I think the MH intake is lower rise too for clearance.

--
John Lebetski
Chicago, IL
77 Eleganza II
Source America First

[Gerald Work]

Hi Darryl,

Based on my experience with them I think all you need to do is tell them it is for a motorhome. They say they do different things internally for motorhome and marine engines plus a different cam for the motorhome application. While there seems to be some differences of opinion on this forum, I found advancing the cam timing four degrees did a good job of lowering the RPMs at which peak torque occurs. Our Royale with the new S&J 455 engine and our Clasco with the stock 455 engine are both geared exactly the same but the Royale seems less labored and more responsive on all kinds of terrane. When asked, S&J supplied a double roller cam gear and chain that could be set at four degrees advanced, zero or four degrees retarded at no additional cost. Most sources I have consulted agree that most traditional engines made after 1971 will benefit from four degrees advance on the cam timing at lower RPMs such as we run in our GMCs because of the need to retard cam timing to meet the
constantly changing emission standards in that era. The racer guys sometimes say retarding the cam timing four degrees will move the peak torque RPM up to the range where they normally run. Some on this forum say it doesn't matter but my experience with the original engine in the Royale (a strong 455 that had been dyno tuned), the stock engine in the Clasco, and this new engine in the Royale suggest it does make a real difference in our application.

Similarly, there seems to be a difference of opinion on this forum about the benefits from the Mondello oil restrictors and/or the Mondello high volume normal pressure oil pump. I asked them to install the oil restrictors (which they did for $125) and I purchased the Mondello oil pump and bolt on pick up tube/screen. They were willing to do a roller cam for $1800 additional as I recall but did not push doing so on these engines. I elected to stay with the flat tappet cam and use GM EOS to make up for any lack of ZDDP in many of the current oils. After lots of research I also elected to stay with a Dick Patterson carb and HEI distributor instead of EFI.

So far, all of these things seem to be working harmoniously together but we won't really know how well for another, oh, say 75,000 to 100,000 miles (grin). Hope this helps.

Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glw...@mac.com
http://jerrywork.com
------------------------------

Message: 13
Date: Sat, 22 Feb 2014 12:40:32 -0600
From: Darryl Meyers <hosp...@att.net>
Subject: [GMCnet] Differences between motorhome and car engines?
To: gmc...@temp.gmcnet.org
Message-ID: <3acdc.5...@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"

OK, I've pretty much made the decision to replace my engine with a "remanufactured" engine. I'll get on the phone Monday to S&J and maybe Motorworks (Thanks Karen and Jerry for your comments). If anyone has any other rebuilders they have had a good experience with I'd like to hear from you.

What is different about the 403/455 engines we use in the motorhome and the same engines in the Toronado and other automotive applications? I understand the cam is different; what is the difference? Anything else? What do I need to ask for to make sure the engine is set up properly for the motorhome?
--
Darryl Meyers

1978 Eleganza II

El Dorado Hills, CA

[Darryl Meyers]

Jerry

That just the kind of information I was looking for.

Thanks

[Darryl Meyers]

KB wrote on Sat, 22 February 2014 12:25

> I would have liked to switch to a 403 (for better mpg's) when we did our replacement, but it was going to be too hard to find all the other stuff (tinwork, manifold, brackets) so we stuck with a 455.
>
> I'd also have loved to go to roller lifters and roller rockers, but the price difference was too much for us (almost doubled the cost). At that point, I'd seriously consider one of JimB's engines instead.
>
> If you talk to S&J and tell them it's for a GMC Motorhome, it'll basically be their heavy truck engine build (Note: the warranty on their heavy vehicle engines is only 12 months, not 5 years like on their car engines).
>
> At a minimum, add a double row roller timing chain; the cost is small (eg Cloyes tru roller or Melling 40409). One of the best GMC engine builders told me privately that oil restrictors are not needed on a hydraulic lifter engine, but strongly suggested a high volume oil pump and pickup (eg Melling EM22FHV and D22FSI). We also went with an RV cam (eg Melling MTO-1, Elgin E-976P, or equivalent), but that's not technically legal on a CA coach that must pass smog tests. I believe Jerry Work went with a standard cam but advanced it 4 degrees.
>
> Sorry, these part numbers are for a 455; I don't know what the 403 equivalents would be.
>
> Hope this helps.
>
>
> Karen
> 1973 23'
> 1975 26'

Karen

Great information, thank you.

I'm very happy with the 403. Even, apparently, on only seven cylinders it ran great and pulled some serious hills without problems on our 2500 mile trip through the Southwest last fall. Gas mileage was down but at the time I figured I was just pushing it a little harder. Thankfully, it didn't self-destruct somewhere in the middle of Utah or Arizona.

Darryl

--
Darryl Meyers

1978 Eleganza II

El Dorado Hills, CA

[Espen Heitmann]

FOI

http://www.gmccoop.com/koba_built_motors.htm
--
1973 26' Parrot green Seqouia in Norway
"Loffen" translates to white bread, it is also a nick name for your.. well you know..down there.. and it was my dog's name, but hey you can also call me Espen ;)

[James Hupy]

I do not have a dog in this hunt, but what the heck, it has never stopped
me before. If you were happy with the 403 even on 7 cylinders, you will be
happy with it running on all 8. With stock final drive gearing, the 403
falls on it's face below 50 mph. The 455 will pull quite well at that rpm.
But, at 62 mph, it is a different story. The 403 will run with the 455 at
that rpm and any faster than 65. If you regear the final drive to 3:70 on
the 403, it will hold it's own with the 455 at any speed.
They are two differently performing engines. Both are good. Add headers and
3" exhaust along with a properly timed cam chain and RV cam and EBL EFI to
the 403 and, my oh my. No contest. But they are both durable, high torque
at fairly low rpm engines, both well suited to the task of moving a 12,000
pound motorhome. Your experience may vary, but check with Migel in LA.
Jim Hupy
Salem, OR
78 GMC Royale 403

[Johnny Bridges]

People seem to have good luxk with the Drew Koba builds Jim Bounds supplies.  You'd have a couple hundred to ship though.  Likewise Mondello.  I'm watching all of you - mine runs fine at 100K... but when it dies, I'll go get another from whomever seems to have the inside track on building them.  Warren Johnsdon is just across the lake, I wonder what he'd get to build one... :) :)
 
--johnny
'76 23' transmode norris
Braselton, GA.


________________________________
From: Darryl Meyers <hosp...@att.net>
To: gmc...@temp.gmcnet.org
Sent: Saturday, February 22, 2014 1:40 PM

Subject: [GMCnet] Differences between motorhome and car engines?

[Dan Borlase]

Jim, I am defiantly having a Caddy 500 built for the stretch. (as we speak) Do you have any suggestions re the build? I have told the builder to maker it stock, and yes, he knows it's for the coach.
PS...the 403 will go to you...assuming you still want it.
I'll have to work with you on getting the gantry system for the swap.

[Johnny Bridges]

Well, the original build has hauled my lump 100K without problems other than a water pump.  If the paperwork is to be believed, the PO had Sirum apply a rebuilt carb.  I see no great need to go beyond what GM did to begin with.  I'd rather spend the money on an engine builder  who is willing to take the time to set everything in it to the same spec GM did to begin with.  Another 100K will probably outlast me.  My toad has all the fancies stuffed in, and takes advantage of them.  I doubt the GMC really needs them.
 
--johnny


________________________________
From: Chris Tyler <dtyl...@tampabay.rr.com>
To: gmc...@temp.gmcnet.org
Sent: Saturday, February 22, 2014 2:57 PM
Subject: Re: [GMCnet] Differences between motorhome and car engines?

[James Hupy]

Dan, I hope that you have located all the engine mounts and accessory
brackets that work in the Motorhome with the Cadillac engine. You will need
them. The a/c compressor is located where the thermostat housing is on the
403, hoses for the radiator are in a different place, the alternator is on
the passenger side, the distributor is in the front of the engine instead
of the rear, power steering hoses and brackets are different than olds,
Carb is different, exhaust manifolds and exhaust pipes will need some
changing as well. But the swap can and has been done before. Larry Wiedner
and Ken Henderson as well as Jim K. all have them and are good sources of
tech info that you can trust. No B.S. from any of them. The gantry is still
at Jerry Work's place. He is in Mexico right now. When he returns, I will
retrieve it. I have to come to Boston Bar after the route 66 rally to help
Kim Davison install a 1 ton front end. If that is not soon enough we will
make a trip with the gantry.
Jim Hupy
Salem, Or
78 GMC Royale 403

[Darryl Meyers]

If you regear the final drive to 3:70 on
the 403, it will hold it's own with the 455 at any speed.
They are two differently performing engines. Both are good. Add headers and
3" exhaust along with a properly timed cam chain and RV cam and EBL EFI to
the 403 and, my oh my. No contest.

Jim

Speaking of the 3:70 I thinking now may be the time to upgrade. Would there be any substantial labor savings in swapping out the drive with the engine R&R now rather than later on its own? If I'm going to spend what I'm going to on the engine I'm not anxious to spend a bunch more on a new FD but if it saves money in the long run I might do it.

[Bill Dolinsky]

How much extra work for a BBC?
--
Bill Dolinsky
Edmonton, Alberta, Canada
1977 Kingsley TZE167V102169

[James Hupy]

Darryl, If you have the entire power unit out, and you had been wanting to
re gear the final drive, this would be an excellent time to make the swap.
Also look carefully at your transmission pans and seals for fluid leaks. If
you have not changed it already, replace the transmission vent with an
angled fitting with a hose barb and run an overflow line so that it does
not discharge onto the headers or mufflers. Good prevention. Also inspect
your motor mounts. Replace them when the engine is out is a no brainer.
Jim Hupy
Salem, Or
78 GMC Royale 403

[James Hupy]

I have never done a Big Block Chevrolet into a GMC, but it has been done.
Takes a modified engine oil pan. The pictures that I have seen bored two
holes on opposite sides of the pan, inserted a tube that was bigger than
the final drive shaft, and welded it into the holes. There used to be some
guys in Sequim, Wa. that sold a kit for the GMC but I believe they are not
in the GMC engine swap business at present. They raced at Bonneville with a
modified GMC quite a few years ago with Chevrolet Big Block for power.
Chev's are a lot cheaper to rebuild than Olds or Cads.

Jim Hupy
Salem, Or
78 GMC Royale 403

[Robert Mueller]

Daryl,

Below you will find links to a number of dyno runs on the 455 engine; I have yet to find any on a 403. If anyone has a dyno run on a
455, 403 or Caddy 500 I'd like to have it IF it was built for a GMC. I DO NOT want dyno runs for hot rods that are setup to run high
rpms. THEY ARE IRRELEVANT!

http://www.gmcmhphotos.com/photos/g6535-dyno-runs-neil-martin-s-455.html

http://www.gmcmhphotos.com/photos/random-photos/p40002-manifolds-vs-headers-4.html

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

-----Original Message-----
From: Darryl Meyers

OK, I've pretty much made the decision to replace my engine with a "remanufactured" engine. I'll get on the phone Monday to S&J and
maybe Motorworks (Thanks Karen and Jerry for your comments). If anyone has any other rebuilders they have had a good experience
with I'd like to hear from you.

What is different about the 403/455 engines we use in the motorhome and the same engines in the Toronado and other automotive
applications? I understand the cam is different; what is the difference? Anything else? What do I need to ask for to make sure
the engine is set up properly for the motorhome?
--
Darryl

[Robert Mueller]

Jim,

Hal Kading installed a new BBC in his Buskirk Stretch, maybe he'll spot this email and reply.

Jim Rosenberg and Dyno Sources up in Sequim are long gone. Along with BBC's they did 8.1 Vortec installations but unlike Dave Lenzi
they had problems. As I understand it on one customer's engine they couldn't get the OEM EFI to work so they put a carb on the
engine.

MOE was the name of the GMC they raced; it had a BBC with a supercharger on it. It was a gutted motorhome that JimB found for them
down in Florida. http://www.gmccoop.com/land_speed_record.htm If you read this article basically JimR screwed JimB! He never even
gave JimB any credit for helping him!

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

-----Original Message-----

From: James Hupy

I have never done a Big Block Chevrolet into a GMC, but it has been done.
Takes a modified engine oil pan. The pictures that I have seen bored two
holes on opposite sides of the pan, inserted a tube that was bigger than
the final drive shaft, and welded it into the holes. There used to be some
guys in Sequim, Wa. that sold a kit for the GMC but I believe they are not
in the GMC engine swap business at present. They raced at Bonneville with a
modified GMC quite a few years ago with Chevrolet Big Block for power.
Chev's are a lot cheaper to rebuild than Olds or Cads.
Jim

[Bill Dolinsky]

Yeah 496 rotating assembly's are inexpensive. Flat top short rod would run nice with peanut ports. I have a set of vortec heads on my 454 ski boat and they work fantastic but they only cc at about 100 cc instead of 118 cc so you would be a little over 10/1 cr with the 496. To much for a towing application, have to run premium in the boat.

--
Bill Dolinsky
Edmonton, Alberta, Canada
1977 Kingsley TZE167V102169

[Robert Mueller]

Mike,

A few comments / observations on your email not meant to attack or criticize; its just how I see it.

I run a 3.21 to 1 (66 Toronado Planetary Gear FD) in Double Trouble. I don't know what the rpm's are at 60 but I do know that at 70
the engine is turning around 2400 rpm. The engine absolutely LOVES that rpm and will do it all day long. The engine was rebuilt by
Ken Frey about 80,000 miles ago and he told me it has a RV cam in it. It has a Paterson Q-Jet and HEI distributor. Oh yeah, I have
watched the cam when I went to pass and the transmission downshifted into 2nd, I noticed the rpm's would go to around 3500 or so.

I am sorry but I am going to disagree with you (and JimB) regarding roller lifters.

Let's look at the pro's first:

1) roller lifters remove the requirement for 1200-1400 ppm of ZDDP in the engine oil (I believe this is JimB's main reason for
incorporating them; he got bit by engine customers putting oil with low levels of ZDDP in engines he had rebuilt and they failed)

2) roller lifters will allow a better cam profile and better engine performance

If anyone can think of more PLEASE feel free to add them!

Now for the con's:

1) roller lifters were available when the 455 was designed, however, the engineers did not see the need for them probably because
engine oil had high enough ZDDP levels and possibly the accountants wouldn't let them spend the money! ;-)

2) if you break in a flat lifter cam properly with high ZDDP engine break in oil and subsequently add ZDDP to bring the level to
1200 - 1400 ppm flat lifters will be just fine

3) installing roller lifters in a 455 with the "squashed" OEM Toronado manifold requires the lifters be machined; click on the link
below and scroll down to Oil supply, look at the lifters in the photo and you'll see the "scalloped" out area on the lifter

http://www.gmccoop.com/koba_built_motors.htm

4) the cost of the roller lifters and cam is a about $500 more than a flat lifters and cam NOT counting what it will cost you to
have them machined

5) the roller lifters have a link to keep them from rotating in their bores and needle bearings between the roller and the shaft
they run on = more parts to fail (the needle bearings in a lifter in my Harley EVO failed on our trip out to Uluru (Ayers Rock) in
2005).

6) I have never seen any hard data (dyno runs) to see if that will justify the added expense and extra parts

I agree roller rockers wouldn't hurt but once again they're not necessary. I won't bother detailing why I believe that as the
reasons are quite similar to what I've noted above.

I agree with the drive gear; in fact I stumbled on to a setup on eBay for an Olds 455 and posted it here. At the time I was told
that they were noisy. I did another search and couldn't find any photos of helical cut gears for an Olds 455. I did find this
website:

http://www.catpep.com/searchengine/searchengine.asp?enginetype=100&parttype=16

And have asked them how quiet their GD-455M gear set was in comparison to a chain drive which I couldn't hear.

Simply put we're NOT building hi-performance screamers for the GMC we're building for reliability and the KISS principle rules! ;-)

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426



-----Original Message-----

[Matt Colie]

glwgmc wrote on Sat, 22 February 2014 16:29

> Hi Darryl,
>
> Based on my experience with them I think all you need to do is tell them it is for a motorhome. They say they do different things internally for motorhome and marine engines plus a different cam for the motorhome application. While there seems to be some differences of opinion on this forum, I found advancing the cam timing four degrees did a good job of lowering the RPMs at which peak torque occurs. Our Royale with the new S&J 455 engine and our Clasco with the stock 455 engine are both geared exactly the same but the Royale seems less labored and more responsive on all kinds of terrane. When asked, S&J supplied a double roller cam gear and chain that could be set at four degrees advanced, zero or four degrees retarded at no additional cost. Most sources I have consulted agree that most traditional engines made after 1971 will benefit from four degrees advance on the cam timing at lower RPMs such as we run in our GMCs because of the need to retard cam timing to meet the
> constantly changing emission standards in that era. The racer guys sometimes say retarding the cam timing four degrees will move the peak torque RPM up to the range where they normally run. Some on this forum say it doesn't matter but my experience with the original engine in the Royale (a strong 455 that had been dyno tuned), the stock engine in the Clasco, and this new engine in the Royale suggest it does make a real difference in our application.

> <snip>
> Jerry Work

Jerry et al,

It was my experience that the peak torque, which always occurs at the crankshaft speed for peak volumetric efficiency, does not change or move with the change of camshaft timing. This is all the same mapped engine and cam we are talking about. The real difference here is I am talking about real numbers and you are thinking about perceived driveability. The two are related but not identical. On the V10, we ran some what we called "thick data". A typical dyno power curve is done at 400 RPM steps. We did the development stuff at 100 and around the torque peak at steps of 50. Only automated controls can do that in a day because it also included spark and fuel loops.

My advice is to talk to the people that ground the cam. They will tell you where to set it. If you have to get keys ground, then do that. (Ground keys are offset to allow more precise cam timing.)

Matt - I still am not used to this keyboard, but we are better.
--
Matt & Mary Colie - Members GMCMI, GMCES Going to MontgomeryThe majestic, once snow covered glacier Chaumière is in for the winter.
'73 Glacier 23 With 4 Rear Brakes that pull as they should
SE Michigan - Twixt A2 and Detroit

[A.]

Can somebody clear this up for me?

Why can't Jim K's mechanics yank Darryl's 403 out, move the applicable parts over to one of these

http://www.appliedgmc.com/prod.itml/icOid/588


and put the new one back in?

Does the Applied GMC website need to be updated to reflect that they don't sell 403 long blocks anymore?

Where is Darryl going to get one shipped from that makes it worthwhile to bypass what Jim K has in stock?
--
'73 23' Sequoia For Sale
'73 23' CanyonLands For Sale
UA (Upper Alabama)
CanyonLands most likely for a parts coach. Sequoia being restored to service.

[Kosier]

Rob,

I do have copies of dyno tests done by Cadillac on the 500, but they are
totally unrealistic as they ran the intake air and the exhaust
through tiny restrictions to simulate the configuration in the car.
However, if you check the July 2000 issue of Hot Rod Magazine,
the article entitled "Torque Pig" gives a good evaluation of the
capabilities. They started with a stock, used Caddy, merely shaved
the heads .020" and replaced the valve springs for caution. (The stock
springs will float the valves at 4200 RPM.) The motor then
responded with 303 HP and 468 ft.lbs. of torque. No RPM given, but since
the stock engine gave max torque at 2000 RPM, you
can assume it was the same. When they started changing parts, things got
even better. I built what I consider to be a much better
package and I find it to be very strong. I would never consider anything
else for a GMC. JMHO

Gary Kosier
77 PB w/500 Cad
Newark, Oh

-----Original Message-----
From: Robert Mueller
Sent: Saturday, February 22, 2014 6:41 PM
To: gmc...@temp.gmcnet.org
Subject: Re: [GMCnet] Differences between motorhome and car engines?

[Robert Mueller]

A,

As far as I know JimK's business is a sole proprietorship; it is not a publically held corporation and therefore the only person
that can answer your questions is Jim.

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

PS - I may be incorrect as Grace may be a co-owner.

-----Original Message-----
From: A.

Can somebody clear this up for me?

Why can't Jim K's mechanics yank Darryl's 403 out, move the applicable parts over to one of these

http://www.appliedgmc.com/prod.itml/icOid/588

and put the new one back in?

Does the Applied GMC website need to be updated to reflect that they don't sell 403 long blocks anymore?

Where is Darryl going to get one shipped from that makes it worthwhile to bypass what Jim K has in stock?

[Matt Colie]

WildBill wrote on Sat, 22 February 2014 18:25

> How much extra work for a BBC?

Bill,

I am curious why you might seek to do this?

Going to the more modern 8.1 makes a limited amount of sense, but that is only if Dave Linze does the build.

Matt

--
Matt & Mary Colie - Members GMCMI, GMCES Going to MontgomeryThe majestic, once snow covered glacier Chaumière is in for the winter.
'73 Glacier 23 With 4 Rear Brakes that pull as they should
SE Michigan - Twixt A2 and Detroit

[Chris Tyler]

I have to disagree with you on that if you are speaking of cam LSA or duration, which most certainly DOES effect peak torque RPM points.

However if you mean advancing/retarding the cam [IE the intake lobe center angle]I agree to a point. Sometimes it does make a big difference in drivability. Advancing usually boosts the responsiveness particularly in low compression smog engines or engines that are a little over cammed. The torque peak may not change all that much but it does seem to move the shape around. Advancing the cam usually raises cranking compression

One thing to check is what LCA the cam is specced at. Some manufacturers build in a certain amount of advance
--
76 Glenbrook

[Robert Mueller]

Gary,

I am suffering from intermittent cases of CRS!

I have a dyno run I got from Jerry Potter: http://www.gmcmhphotos.com/photos/g6551-dyno-run-cadillac-500.html

I also have the Torque Pig article; I think you sent it to me!

[mike foster]

Do the same things to the 455 and it's no contest. I can build a 455/550 lbft for a lot less than changing the ring/pinion and adding EFI!!! And none of these things are winning any MPG contests.

A friend of mine who is a SBC guru (12,500 rpm 287) bought a 1968 cross/ram, dual quad, chambered exhaust Z/28 back in 1968 to street race down in Charleston, SC. He did everything he could to that engine but on Saturday night on Bee's Ferry Rd. or Sunday afternoon out on Wadmalaw Island at Jimmy Smalls station (THE best drag racing in SC at that time) Bill Newtons, 494 Tunnel Port 56 T-bird or Randy Nashes 427 open chambered Nova put his little 302 in the trailer. He finally turned it into a modified eliminator track only car.

CID makes creating torque EASY and INEXPENSIVE.


James Hupy wrote on Sat, 22 February 2014 16:17

[Bob de Kruyff]

Darryl wrote on Sat, 22 February 2014 11:40

> OK, I've pretty much made the decision to replace my engine with a "remanufactured" engine. I'll get on the phone Monday to S&J and maybe Motorworks (Thanks Karen and Jerry for your comments). If anyone has any other rebuilders they have had a good experience with I'd like to hear from you.
>
> What is different about the 403/455 engines we use in the motorhome and the same engines in the Toronado and other automotive applications? I understand the cam is different; what is the difference? Anything else? What do I need to ask for to make sure the engine is set up properly for the motorhome?

As usual, you got a lot of opinions (and no facts) and no one answered your question. There are indications that the 455 may have had a specific cam but it's not totally proven in the various installations people have disected. The 403 does not appear to have a specific cam from the passenger car versions.
--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Robert Mueller]

G'day,

I just stumbled on to this: http://www.gmcmhphotos.com/photos/random-photos/p52910-dyno-run-405-vs-455.html

Regards,
Rob M.

[Bob de Kruyff]

USAussie wrote on Sun, 23 February 2014 19:48

The 2 engines have different characters, however I have driven 455's that were faster than the 403 and the converse. The 403 is a bit higher revving which is nice at higher speeds and you want to pass. It also seems to have less reciprocating mass and is a bit livelier. however, most people would fail any blind test.

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Neil Martin]

Bob

Rob posted my dyno tune progression above.

The cam is a Camp Cam roller,

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1182&sb=0

But note how much power and torque came from tuning after the build.

Still running strong.

Just my opinion. :)
--
Neil
76 Eleganza
Los Angeles

[Robert Mueller]

Neil,

Thanks for that information! I am going to contact Comp Cams and get them to compare your cam to the flat tappet cam that I have in
my GMC.

Your dyno runs clearly show what can be gained through dyno tuning of an engine.

That's NOT an opinion that's a FACT!

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

-----Original Message-----

From: Neil Martin

Bob

Rob posted my dyno tune progression above.

The cam is a Camp Cam roller,

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1182&sb=0

But note how much power and torque came from tuning after the build.

Still running strong.

Just my opinion. :)
--
Neil