[GMCnet] replacing driver's side head on a 455

[Robert J. Gogan via Gmclist]

Blew out a water pump last summer and overheated the engine trying to pull over. New water pump installed, but engine is running hot despite a tested
good thermostat and good radiator especially on long uphill grades. Pressurized coolant system and found a leak down without any external antifreeze
leaks.

Did cylinder compression tests:

All cylinders 150-160 psi on my rebuilt 455 engine with 55,000 miles on it EXCEPT cylinder #5 which is reading 55-60 psi.

Figure I've got one or more of the following:
1) overheated cracked head at cyl #5,
2) overheated warped head and blown head gasket at cyl #5
3) burned valves or seats at cyl #5 or
4) piston ring failure at cyl #5.
Don't think it's a cracked block. Had that before and oil and antifreeze leaking out was pretty evident.

Starting the disassembly process to replace the J head on the driver's side:

After removing the driver's side exhaust header (just installed two years ago) found that the nice thick gasket that Jim K sold me was broken up in
the web area between the exhaust ports. No external leaks yet.

Same thing happened on the passenger side last year, but the outside of the gasket broke down it that area and it leaked.

The original heads were designed for manifolds and it was not necessary for the dividing web in the central exhaust to press against the gasket web
onto the exhaust header. Talked to my head rebuilder about this and he was willing to put a bead of weld onto the head web to build it up to engage
the web portion of the gasket. However, he suggested that I just cut the web out of the gasket to prevent the exhaust pressure from tearing it up and
ripping out the more important peripheral gasket.

This is, for sure, the first of many questions that I will have during this rebuild process:

Should I build up the exhaust port web with a weld and machine it to engage the web portion of the gasket or should I just cut out the web part of the
gasket so it doesn't tear out the important peripheral sealing portion of the gasket?


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[Emery Stora via Gmclist]

I had an overheating problem about 2 years ago on a fairly recently rebuilt 455 engine.
It turned out when the engine overheated two of the center pistons swelled and rubbed on the cylinder walls generating a lot of heat which ruined the engine.

I haven’t made a trip with the latest engine yet due to Covid. Hopefully this summer or fall we’ll take a trip.

Emery Stora
77 Kingsley
Frederick CO

> On Mar 8, 2021, at 1:48 PM, Robert J. Gogan via Gmclist <gmc...@list.gmcnet.org> wrote:
>
> Blew out a water pump last summer and overheated the engine trying to pull over. New water pump installed, but engine is running hot despite a tested

[Matt Colie via Gmclist]

Robert,

I am sure Jim Hupy will agree, but after tearing down many engines, the thing I really want to tell you is (I'm not just sure here)

Don't kill your chickens before you find them??

There have more than a few instances in my life that I was sure something major was wrong and the only thing that was a big issue was "the nut behind
the wheel".

It is very possible that all you actually have is a bad intake gasket (real easy bet) and a bad head gasket.

But please, get it open and then tell us more.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

[John R. Lebetski via Gmclist]

If you throw out this “warped head” theory and go with just a bad head gasket you have a win. Now sell the headers (proven no gains) and bolt on
2 manifolds and done.
I had a similar “brain logic diagnosis” just a couple weeks ago. Follow me here. My XJ with 300K miles was weekly low on coolant in the overflow.
Kept adding 50/50. It would also start in the morning with 1 dead cylinder more and more often. Reving it would clear it and it would not miss all
day at any speed. Finally it started with the miss and would not clear. Cyl 2 missfire. Pulled plug expecting the worst. Head gasket. Hoped for
carbon in gap, but no, LOOKED fine. Got the METER and Ohmed center to side. Had some value not open circuit. Also metered center to tip and that was
100k too high. So the plug was arcing internally and not visibly bad. 6 new correct plugs and under $20.
Aa for coolant loss, removed cap (fairly new) and cleaned plastic neck with cloth and rinsed cap off. Put a light film of grease under the cap hold
down tabs. This earless type cap was now way easier to palm and turn. Turned back and forth several times to get a better seal on plastic neck. No
more high speed coolant loss past outer gasket.
Moto is everything pointed to head gasket and it was totally two other issues and an easy fix. Don’t throw out baby with bath water.
--
John Lebetski
Woodstock, IL
77 Eleganza II

[Robert J. Gogan via Gmclist]

I have replaced so many cracked exhaust manifolds that I don't even remember the count. Finally switched to headers and increased the carburetor jet
sizes by 2. I'll never go back to manifolds with the shock cooling and cracking they were susceptible to with a lean carb.

[James Hupy via Gmclist]

There are only two types of cast iron exhaust manifolds. Cracked ones, and
ones that haven't cracked yet. The real key to prevention is, rich mixture
combined with a soft cushion type gasket PROPERLY torqued, and a non rigid
connection to the exhaust pipes. If they have a white appearance near the
ports, you are too lean on the w.o.t. mixture.
Jim Hupy
Salem, Oregon

[Robert J. Gogan]

More info obtained an how to manage the head exhaust center port webs:
The knowledgeable person who privately responded to me highly recommended building the divider out flush on the Olds center exhaust port. It is done
by putting a weld bead down then machining it flush. Here is the rationale:
With the use of headers, the value in exhaust breathing improvement and cooling comes from having one pipe per cylinder. The merging effect at the
collector will aid the pull from each pipe. If the web is not built up, the value of having headers is not fully realized. Simply removing the divider
in the header gasket might prevent the gasket from blowing out, but it will just allow exhaust gases to bump into the divider in the header and not
provide the separate pipe for each exhaust port.

I have purchased the aluminum intake manifold designed after our original GMC motorhome low profile cast iron design with modifications for clearance
of our carbs. It eliminates the original intake manifold exhaust cross over.
Next question:
What is the best gasket to achieve a leak free seal in mounting that aluminum manifold? Applied GMC seems to have a gasket without the crossover port
in it which seems idea. However, is it better to install the gasket with the stainless steel crossover port plates to keep the gasket from
deteriorating from the hot exhaust gases or is this not necessary?

[Ken Burton]

I would install the stainless blocking plates to keep the hot exhaust from getting to the gasket. The Dick Paterson blocking plate kit has the
correct thickness plate and matching gasket thickness to provide a correct seal. Many intake gaskets sold are too thick. Call Dick at Springfield
Ignition.

http://www.springfield-ignition.com/
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[John R. Lebetski]

Yep the common 3-5 and 4-6 ports don’t create a clear pulse drive in those header tubes, which then causes poor scavenging in 1, 7, 2, and 8.

--
John Lebetski
Woodstock, IL
77 Eleganza II

[James Hupy]

Yep, you would probably notice a loss in torque and horsepower around 5500
- 6000 rpm or so. 1800 to 3600? Bet you not much difference.
Jim Hupy
Salem, Oregon

On Tue, Mar 16, 2021, 6:57 AM John R. Lebetski <gransp...@gmail.com>
wrote:

[Ken Henderson]

Sorta like my answer to the frequent question, "Did you notice any power
loss when you went back to OEM from the Edelbrock Performer intake
manifold": "Not below 4000 rpm."

Ken H.

[Robert J. Gogan]

Next issue is my aluminum intake manifold that is an exact copy of the original GMC motorhome cast iron manifold. I bought it when it was first
manufactured 10 years ago and now because of this bad head issue I am finally getting ready to install it. It came without any paint and despite it
being aluminum, I suspect it should be painted. Any advice on painting an aluminum intake manifold? Several vendors are selling the 500 degree
Fahrenheit original 455 blue metallic paint but I don't know if that will adhere to the aluminum. Is there a special prep needed and do gasket
surfaces get painted also?

[Johnny Bridges via Gmclist]

If you choose to follow JohnLs suggestion and revert to exhaust manifolds, Make sure you have both manifolds in hand, with smooth surfaces and no
cracks. One side is made of unobtainium, common only to the GMC motorhome fitted with a 455 engine.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Matt Colie]

jhbridges wrote on Mon, 22 March 2021 12:03

> If you choose to follow JohnLs suggestion and revert to exhaust manifolds, Make sure you have both manifolds in hand, with smooth surfaces and no
> cracks. One side is made of unobtainium, common only to the GMC motorhome fitted with a 455 engine.
>
> --johnny

I have told, but I have not confirmed that Cinnabar can supply new exhaust manifolds.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

[Matt Colie]

Matt Colie wrote on Mon, 08 March 2021 17:26

> Robert,
>
> I am sure Jim Hupy will agree, but after tearing down many engines, the thing I really want to tell you is (I'm not just sure here)
> Don't kill your chickens before you find them??
> There have more than a few instances in my life that I was sure something major was wrong and the only thing that was a big issue was "the nut
> behind the wheel".
> It is very possible that all you actually have is a bad intake gasket (real easy bet) and a bad head gasket.
> But please, get it open and then tell us more.
>
> Matt

Robert,

It sounds like you are getting ready to close the engine back up.

What was the cause of the compression loss?

[Robert J. Gogan]

Still waiting to paint the aluminum intake manifold before I take the cast iron one off. Advance auto had to order the Duplicolor high temp engine
paint that should be for an Olds 455. Have to keep things authentic. I get stopped so often at gas stations with inquisitive people wanting to see
my vintage coach, I'd be embarrassed if I didn't have the authentic Olds blue paint on the engine.

BTY, Head is still on. Will announce the cause of the low compression as soon as it is discovered. The replacement head is at the Head rebuilder for
the second time. This time the head is getting the divider (web) between the inside exhaust ports welded up to the gasket surface. Hopefully, this
will help the header pipes produce even exhaust back pressure and cooling and keep my Remflex gasket from blowing out a third time.

[Emery Stora via Gmclist]

Do you really lift the engine cover and invite people in for people at a gas station?

That’s a lot more than I do.

Emery Stora

> On Mar 22, 2021, at 5:30 PM, Robert J. Gogan <rgo...@ameritech.net> wrote:
>
> Still waiting to paint the aluminum intake manifold before I take the cast iron one off. Advance auto had to order the Duplicolor high temp engine

[Emery Stora via Gmclist]

I put a thin bead of Permatex Ultra Copper sealant on both sides of my Remflex gasket and it has never blown out. You might try it. Your manifold might have a slight distortion or pitting that could cause the gasket to fail. Two failures and anticipating a third one isn’t normal.

Emery Stora
77 Kingsley

> On Mar 22, 2021, at 8:16 PM, Emery Stora <emery...@icloud.com> wrote:
>
> Do you really lift the engine cover and invite people in for people at a gas station?

[Robert J. Gogan]

Compression loss was from head gasket web failure between cylinders #5 and #7. I believe this was from inadequate torque on the head bolt at that
location. Found that all the head bolt bores in the block were the same depth but on chasing the threads found that the threads did not extend deep
enough on the bore in the block on the outboard side between #5 and #7. Confirmed this by looking down the bore. Dealt with it by putting a Grade #8
thick washer under that head bolt. I could have cut the bolt shorter or tapped the hole deeper with an end tap, but this was the simplest solution.
All the bolts torqued down as expected.
Now I am dealing with the aluminum intake manifold which is turning out to be less than perfect. New post to follow.

[Jim Kanomata]

Robert,
Most of us that know engines see no advantage to coat the Al. intake.
Yes Al. Oxidizes more than steel, but you should be more concerned about
sealing the intake to the head as that is where lot of problems develop.

On Thu, Jun 24, 2021 at 8:05 AM Robert J. Gogan <rgo...@ameritech.net>
wrote:

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