The faces that mate with the head need to be true (flat ,square, etc ) with
the head. THis sometimes requires machining. No need to worry about the back
side where the fasteners go.
Dave Handley
51 GMC 5 window
-----Original Message-----
From: Julie or Colin <juliecolin@earthlink.net>
To: oletrucks-digest@autox.team.net <oletrucks-digest@autox.team.net>
Date: Sunday, July 30, 2000 5:13 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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