Exhaust Manifold Progress and ?

[john wright]

Rick,
I would not install that type of exhaust manifold gasket. If it is a FelPro
#90021 or similar it has a poor fit and you will be replacing it much
quicker. Cinnabar in newsletter #14 stated to avoid that type of gasket
and use the FelPro 1439 gasket. That is the one that I uses along with
Permatex Ultra Copper high temp silicone gasket maker. I lightly apply
a coat of the silicone and then torque the bolts to 25 Let set for 24
hrs before starting engine. This will allow the sealant time to cure.
But sure that you use something like never-seize on the bolts to prevent
them from seizing in the heads. Another alternative is to go to the
solid copper gasket. It is a Mr. Gasket brand that is available from
Jeg's under part # 720-7170 $31.99. The FelPro 1439 is $28 bucks, so
the choice is yours

J.R. Wright
GMC GreatLaker
77 Eleganza II
Michigan

>
> The two first noticible problems when we got our coach were the lack of a
> dipstick (or tube) and a major exhaust leak. Those two are going to be
> corrected this weekend.
>
> I opted to order the "Toronado" short dipstick, still available from Olds
> ,about $17.00 for both stick and tube. I'll have to raise the floor to check,
> but thats OK.
>
> I had the manifold magnafluxed, and finding no cracks had it machined as it
> had warped some. Painted it with header paint (olds blue)...new bolts and
> studs.
>
> Question??? The new gasket has a "graphite" side and a shiny metal
> side...does it matter what side goes to the block and what side goes to the
> manifold?
>
> "Rick"

 

[loren \(skip\) newhouse]

> ...........Question??? The new gasket has a "graphite" side and a shiny metal
> side...does it matter what side goes to the block and what side goes to the
> manifold?
>
> "Rick"

Hi Rick,

You should consider not using a gasket on the manifold. It can impede the
transfer of heat from the manifold to the block which can cause further warping.
After I had mine machined I installed without a gasket. I used a "Permatex"
copper sealant. No problems so far. Also make sure you use anti-seize on the
bolts. That's what I did.

Skip Newhouse
'75 Avion
Western MD

 

[richard waters]

Rick,
What do you think about the claims that Cinnabar makes about
recalibrating carburetors as a way to reduce the excessive heat
generated from too lean mixtures? That supposedly contributes
to the failure of exhaust manifolds and gaskets.
I had my manifolds redone recently by Cinnabar (new manifold on
driver side and passenger side machined flat) and they used Fel-Pro
gaskets. Plus they recalibrated the carburetor.
I hope I get more then 6,000 miles out of the job they did!
Richard Waters '76 PB, Troy, MI

> So in the real world, most of us need some kind of gasket. I first tried
> the heavy-duty (Fel-Pro?) gasket Cinnabar sells. Sealed nicely, but ~6,000
> miles later one side was leaking again. Then I read about the Mr. Gasket
> solid copper gaskets.
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
>
>

 

[russ bethel]

They will leak in about 10 to 15 thousand miles. If you check the torque
every 2 to 3 thousand miles they may last a little longer. That is how they
worked for me.

Russ Bethel
rbethel
- -----Original Message-----
From: RickStapls
To: gmcmotorhome
Date: Friday, May 14, 1999 22:32
Subject: Re: GMC: Exhaust Manifold Progress and ?

>
>> Is copper less likely to "blow out" or is it one of those "state of the
>art"
>> items which you need digital instrumentation to prove their superiority?
>
>Rick,
> By now you've seen the posts from other members telling you not to
bother
>with composite exhaust gaskets, so you have an idea of what you're up
against.
> Originally (from the factory), our GMCs came with no exhaust gasket
>whatsoever. This is ideal, as it allows the manifold to expand and
contract
>at will without damaging (chewing up) a gasket. (The manifold can slide
more
>or less freely across the face of the cylinder head.) Also, the manifold
can
>dissipate some of its heat back into the water-cooled head. Unfortunately,
>this ideal system only works if the mating surfaces of head and manifold
are
>perfectly straight and flat. If you have the heads off and can resurface
>everything, try it.
> So in the real world, most of us need some kind of gasket. I first
tried
>the heavy-duty (Fel-Pro?) gasket Cinnabar sells. Sealed nicely, but ~6,000
>miles later one side was leaking again. Then I read about the Mr. Gasket
>solid copper gaskets. These seem like an ideal compromise. The smooth
>surface allows the manifold to expand and contract, the solid copper
>transfers heat as well as possible from manifold to head, and yet it
provides
>enough sealing ability to qualify as a "gasket". I've only had mine in
there
>about 2,000 miles. So far, so good.
> HTH.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
>