The bolts holding the exhaust to the intake manifolds should be the last
ones you tighten. Assemble with them loose and assure there is enough play
for the faces to be in the same plane against the head. If so tighten the
bolts holding against the head the then tighten the four bolts holding the
intake and exhaust together last.
If this doesn't work there is a possibility that someone mixed and
matched manifolds together that don't fit. Sometimes on Chevy manifolds
there are differences between years, maybe so on GMC's too.
I wouldn't worry to much about the back faces if they are reasonably
close.
Grant
50 Chevy 3100
52 GMC 150
Julie or Colin wrote:
> 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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