Colin,
Anything you can do to align the manifold mating surfaces will help in
installation and prevent leaks and blown gaskets. These weren't much of a
precision fit from the factory, there is lots of room for improvement. The
exhaust manifold particularly will distort with age. I posted an article on
this subject in the "tech" section of http://www.Chevytrucks.org a while
back. The Clifford one-piece gasket is a big help, as are new pilot rings.
You can make your own out of exhaust tubing.
You have my eternal envy for having a Bridgeport at your disposal!
Jack Halton
51 GMC 1/2 ton
Winter Park FL
----- Original Message -----
From: "Julie or Colin" <juliecolin@earthlink.net>
To: <oletrucks-digest@autox.team.net>
Sent: Sunday, July 30, 2000 6:03 PM
Subject: [oletrucks] GMC 248 Intake/Exhaust Question
> Maybe you guys can answer this for me. I am cleaning up my exhaust and
> intake manifolds prior to reassembling after blowing out the exhaust
> gasket. It's been a long process--nearly every bolt either chiseled off
> or drilled out. I mounted the intake on top of the exhaust and found
> that the flange faces are not in the same plane. The manual calls for a
> max of .010" warpage between faces of the same manifold, but no spec is
> given when they are assembled. The cylinder head flanges are in the
> same plane. I can take this to work and mill the manifolds while they
> are assembled, but I wanted to ask if anyone knows if there might be a
> reason if they are made this way intentionally (thermal expansion,
> maybe?) before I cut them. Also, should I spotface the back side of
> the flanges to equal thickness after milling, or does this matter--I am
> thinking of equal clamping pressures. Any ideas before I fire up the
> Bridgeport? BTW, the intake flange faces extend past the exhaust flange
> faces by approx. 1/32". This makes sense to me if the exhaust manifold
> has been surfaced by itself to correct prior warpage. Doesn't seem to
> me that this can possibly seal correctly the way it is. Any ideas?
>
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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