cylinder heads for 1976 Palmbeach

[patrick flowers]

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Patrick Flowers
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The GMC Motorhome Page
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From: "Thomas G. Warner"
To: "'gmcmotorhome'"
Subject: cylinder heads for 1976 Palmbeach
Date: Sun, 22 Mar 1998 09:12:28 -0500

I am renovating a just purchased 1976 palmbeach and have found a broken =
bolt boss on the right cylinder head that is used to attach the exhaust =
manifold to the cylinder head. The previous mechanic(?) used a 1 1/2" =
bolt in the hole which of course is to long and broke the boss.

Can I use any cyllinder heads from 1968-1976 on the engine? Will =
different ones change the compression ratio
?
Tom Warner

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[scott woodworth]

Tom,

Oldsmobile engine are one of my specialties, so I can tell you the
following with confidence:

Look on the side of the driver's side head next to the front spark
plug. There will be a letter there like "J" or something. Just go to
the junkyard and get another Olds head with the same letter. Yes, each
different letter head has slight differences. As long as you use the
same letter, you will be assured the head you buy is identical to the
head you already have.

- -Scott Woodworth

 

[rich and dottie major]

Scott,

I read your message below and would like to question your Olds knowledge a
bit. I have a '78 Kingsley with a 403. The heads exhaust manifolds seem
to be leaking a bit. I also noticed that there are gaskets on these
manifolds. I was under the impression that Oldsmoble did not use gaskets
for the manifolds. Did this procedure change in '78???? Thanks for any
assistance you may offer.

Rich Major
'78 Kingsley
Sugar Land, Texas

> Tom,
>
> Oldsmobile engine are one of my specialties, so I can tell you the
> following with confidence:
>
> Look on the side of the driver's side head next to the front spark
> plug. There will be a letter there like "J" or something. Just go to
> the junkyard and get another Olds head with the same letter. Yes, each
> different letter head has slight differences. As long as you use the
> same letter, you will be assured the head you buy is identical to the
> head you already have.
>
> -Scott Woodworth

 

[scott woodworth]

Rich,

The GMC motorhome shop manual does not show the use of exhaust
manifold gaskets. There's a good reason not to use them in this
application.

Motorhome service causes a great amount of heat. The engine is
under a moderate to heavy load most of the time. I'd be willing to bet
that the exhaust manifolds can get dull cherry red during long hill
climbs. Using gaskets will insulate the exhaust manifolds from the
heads. That leads to overheating and cracked manifolds.

The best solution is to take them down to a good machine shop and
have the checked for cracks then have them surfaced. Make sure that
they take off only as much metal as necessary.

Reinstall the manifolds without gaskets and torque the center bolts
to 25 foot pounds. Then torque the outside bolts to 15 foot pounds.
That allows the manifolds to expand lengthwise when they get really hot.
That way, they won't crack. Leaving the gaskets out will allow the
water cooled heads to sink more heat from the manifolds. This tip comes
from the book Trailer Life's Rx for Rv Performance and Mileage by John
and Estes, Bill Geraghty. (Out of print)

Note: Do not use galvanized bolts on your manifolds if you ever plan to
remove them. Please use grade 5 or grade 8 bolt and put anti seize on
them or dip them in plain unflavored Milk of Magnesia.

- -Scott Woodworth

P.S. The 403 heads are 4C.

 

[thomas g. warner]

Scott I understand the head designations. I have an extra set of E heads form a 1969 toro. Will they fit. I understand that all 1968-1976 455 heads will fit. Is this true?

- -----Original Message-----
From: Scott Woodworth [SMTP:myvair]
Sent: Sunday, March 22, 1998 9:23 PM
To: gmcmotorhome
Subject: Re: GMC: [Fwd: cylinder heads for 1976 Palmbeach]

Tom,

Oldsmobile engine are one of my specialties, so I can tell you the
following with confidence:

Look on the side of the driver's side head next to the front spark
plug. There will be a letter there like "J" or something. Just go to
the junkyard and get another Olds head with the same letter. Yes, each
different letter head has slight differences. As long as you use the
same letter, you will be assured the head you buy is identical to the
head you already have.

- -Scott Woodworth

 

[thomas g. warner]

Rich excellent idea but I would not put them on without a gasket. The original GMC engines did not use gaskets as you indicate but they did use a substance similar to pyro putty to ensure a good seal. I believe Clarence Buskrk uses solid copper gaskets to both seal the manifold to cylinder head, and provide better heat conduction to the water jacketed cylinder heads.

- -----Original Message-----
From: Scott Woodworth [SMTP:myvair]
Sent: Sunday, March 22, 1998 11:17 PM
To: gmcmotorhome
Subject: Re: GMC: [Fwd: cylinder heads for 1976 Palmbeach]

Rich,

The GMC motorhome shop manual does not show the use of exhaust
manifold gaskets. There's a good reason not to use them in this
application.

Motorhome service causes a great amount of heat. The engine is
under a moderate to heavy load most of the time. I'd be willing to bet
that the exhaust manifolds can get dull cherry red during long hill
climbs. Using gaskets will insulate the exhaust manifolds from the
heads. That leads to overheating and cracked manifolds.

The best solution is to take them down to a good machine shop and
have the checked for cracks then have them surfaced. Make sure that
they take off only as much metal as necessary.

Reinstall the manifolds without gaskets and torque the center bolts
to 25 foot pounds. Then torque the outside bolts to 15 foot pounds.
That allows the manifolds to expand lengthwise when they get really hot.
That way, they won't crack. Leaving the gaskets out will allow the
water cooled heads to sink more heat from the manifolds. This tip comes
from the book Trailer Life's Rx for Rv Performance and Mileage by John
and Estes, Bill Geraghty. (Out of print)

Note: Do not use galvanized bolts on your manifolds if you ever plan to
remove them. Please use grade 5 or grade 8 bolt and put anti seize on
them or dip them in plain unflavored Milk of Magnesia.

- -Scott Woodworth

P.S. The 403 heads are 4C.

 

[scott woodworth]

Tom,

Yes your Toronado "E" heads will fit, however they do not have the
induction hardened exhaust valve seats like the "G" ,"J" and "K" heads
do. You should have your machinist install aftermarket hard seats.

One problem with Olds heads is that they have huge heat riser
passages. I believe that Olds engineers did this on purpose to improve
cold start driveability. The problem is that on the motorhome
application with it's attendant heavy engine loading and heat, the
intake gets overheated. This will cause power loss, fuel percolation
and detonation.

As a further detriment, the exhaust gas reversion back and forth
through the intake heat riser passages causes a 5-10 HP power loss
because of cross cylinder exhaust contamination. The center 4 cylinders
are the ones affected. #3 will contaminate #4's intake charge due to
#4's exhaust valve still being open on the beginning of the intake
stroke. Same with #5 contaminating #6.

A very good upgrade, which I have done to my Olds 403 heads is
install Mondello heat riser plugs. Then drill a 1/4 inch hole through
each one to give just enough heat to warm the intake. My machinist
installed mine with JB weld and resurfaced the intake port surface.
It's hard to tell that they aren't part of the original casting now.
This modification will slow down the choke opening action, so it's best
to use an electric choke.

Do your "E" heads have provisions for smog tubes in the exhaust
ports? If so, remove them and screw pipe plugs in the holes. Then have
your machinist die grind those bumps down level with the rest of the
port. You will pick up another 5 HP. See? Cheap horsepower and your
heads were already at the machine shop for new seats anyway. ;- )

Here's where I get my Olds parts at:

MONDELLO PERFORMANCE PRODUCTS, INC.
1103 Paso Robles Street, Paso Robles, California 93446
(805) 237-8808 - Fax (805) 237-8814
http://www.tcsn.net/mondello/

- -Scott Woodworth

 

[bartz paul]

Scott:

Here is what Joe Mondello's says to your below exhaust gas reversion
comments:

From: Mondello Tech School [SMTP:mondello]
Sent: Wednesday, April 01, 1998 1:20 PM
To: Bartz, Paul
Subject: Re: Olds Heads

Paul, I do not believe in gas reversion on low lift low RPM Olds
engines.

Joe Mondello

Do you still feel that what you stated is valid?

Paul Bartz
> -----Original Message-----
> From: Scott Woodworth [SMTP:myvair]
> Sent: Wednesday, March 25, 1998 2:08 AM
> To: gmcmotorhome
> Subject: Re: GMC: [Fwd: cylinder heads for 1976 Palmbeach]
>
> Tom,
>
>
> One problem with Olds heads is that they have huge heat riser
> passages. I believe that Olds engineers did this on purpose to
> improve cold start driveability. The problem is that on the motorhome
> application with it's attendant heavy engine loading and heat, the
> intake gets overheated. This will cause power loss, fuel percolation
> and detonation.
>
> As a further detriment, the exhaust gas reversion back and forth
> through the intake heat riser passages causes a 5-10 HP power loss
> because of cross cylinder exhaust contamination. The center 4
> cylinders are the ones affected. #3 will contaminate #4's intake
> charge due to #4's exhaust valve still being open on the beginning of
> the intake stroke. Same with #5 contaminating #6.
>
>
>

 

[scott woodworth]

Paul,

I get my info from Joe directly and articles he's written for
various publications. If he says he doesn't believe that exhaust gas
reversion doesn't have adverse effects on engines with low lift/overlap
cams, I have no reason to disbelieve him.

The main reason for installing the plugs is to keep the intake
cooler to increase VE (volumetric efficiency) and cut down on that
infernal pinging the these engines suffer from.

The info pertaining to the heat riser plugs is from a phone
conversation I had with Joe and was based on a 403 with their lowest
level cam in a street stock driven application.

I run a 403 in my 1980 Seville. It's got all kinds of power. It's
a weird feeling to feel the front wheels break traction so easily.

- -Scott Woodworth

 

[bartz paul]

Scott:

No offense intended, but hope you would agree that perhaps it would be
better off if everything attritributed to Jo M would be evaluated first
for application to the GMC Motorhome rather than subsequently found to
be taken out of context?

Paul

> -----Original Message-----
> From: Scott Woodworth [SMTP:myvair]
> Sent: Friday, April 17, 1998 2:40 PM
> To: gmcmotorhome
> Subject: Re: GMC: [Fwd: cylinder heads for 1976 Palmbeach]
>
> Paul,
>
> I get my info from Joe directly and articles he's written for various
> publications. If he says he doesn't believe that exhaust gas
> reversion doesn't have adverse effects on engines with low
> lift/overlap cams, I have no reason to disbelieve him.
>
> The main reason for installing the plugs is to keep the intake cooler
> to increase VE (volumetric efficiency) and cut down on that
> infernal pinging that these engines suffer from.
>
> The info pertaining to the heat riser plugs is from a phone
> conversation I had with Joe and was based on a 403 with their lowest
> level cam in a street stock driven application.
>
> I run a 403 in my 1980 Seville. It's got all kinds of power. It's a
> weird feeling to feel the front wheels break traction so easily.
>
> -Scott Woodworth

 

[scott woodworth]

>
> Scott:
>
> No offense intended, but hope you would agree that perhaps it would be
> better off if everything attritributed to Jo M would be evaluated first
> for application to the GMC Motorhome rather than subsequently found to
> be taken out of context?
>
> Paul

What can I say to that? You're worried about a non issue here. The
exhaust crossover contaimination thing is just a side issue. I would
still go with Joe's recommendation about the plugs.

I've had a 350, a 403 and a 455 and without the heat riser plugs,
they've been susceptible to overheating their intake manifolds. The
reason I know is because once the plugs are installed, they run so much
better without any pinging. Getting off the expressway is the worst
time for that. The manifold will be so hot, pinging is guaranteed.

- -Scott Woodworth

 

[bartz paul]

Scott:

What does the temperature of the intake manifold have to do with
pinging? Thought that was a timing issue of when each cylinder fires?

Paul Bartz

> -----Original Message-----
> From: Scott Woodworth [SMTP:myvair]
> Sent: Friday, April 17, 1998 5:05 PM
> To: gmcmotorhome
> Subject: Re: GMC: [Fwd: cylinder heads for 1976 Palmbeach]
>

>
> Scott:
>
> No offense intended, but hope you would agree that perhaps it would be
> better off if everything attritributed to Jo M would be evaluated
> first for application to the GMC Motorhome rather than subsequently
> found to be taken out of context?
>
> Paul
>
> What can I say to that? You're worried about a non issue here. The
> exhaust crossover contaimination thing is just a side issue. I would
> still go with Joe's recommendation about the plugs.
>
> I've had a 350, a 403 and a 455 and without the heat riser plugs,
> they've been susceptible to overheating their intake manifolds. The
> reason I know is because once the plugs are installed, they run so
> much better without any pinging. Getting off the expressway is the
> worst time for that. The manifold will be so hot, pinging is
> guaranteed.
>
> -Scott Woodworth

 

[scott woodworth]

>
> What does the temperature of the intake manifold have to do with
> pinging? Thought that was a timing issue of when each cylinder fires?

Pre ignition is a condition in which the fuel mixture burns
prematurely due to high combustion chamber temprature. High combustion
chamber temperature can be caused by any number of factors such as
timing, water temperature, INCOMING FUEL/AIR MIXTURE TEMPERATURE, engine
compartment temperature, etc. It doesn't matter where the source of
heat comes from.

In our beloved Oldsmobile engines, the greatest source of heat comes
from that oversized exhaust crossover. In the GMC motorhome
application, the poor thing is sitting in a cramped engine compartment
behind a huge very hot radiator above a very hot transaxle running at
high throttle openings most of the time pulling 14,000 pounds around.
To add to the heat load, the transmission and engine oil coolers add
their heat load to the engine coolant.

Notice were the greatest source of heat lies. It's easy enough to
fix. You only need enough heat to keep carburetor ice from forming.

- -Scott