Bad manifold gaskets

[dmaxweb]

Originally Posted by Bob Bidonde

Here's are some tips for installing the manifold gaskets:
> Take out the 2 bolts connecting the intake manifold to the exhaust manifold;
> Install the manifolds being sure to use gland rings in each exhaust port;
> Fit each ring beforehand, so it has a 0.06" end gap for expansion. The expansion gap prevents a ring from buckling, going into the exhaust pipe and winding-up in the muffler;
> Snug the manifold attachment nuts, but do not torque them to an amount that flattens the cup washers. The cup washers are actually springs that take-up thermal expansion which tends to loosen the manifold connections to the block;
> There is likely to be a gap between the intake & exhaust manifold surfaces where the bolts were removed:
o Shim the gap closed with metal sheet stock to retain the hot spot conduction heat transfer function for warmup of the intake manifold or,
o Leave the gap open and loosely install the 2 bolts connecting the manifolds so it looks correct or,
o Leave the 2 bolts out.

Running with a gap between the manifolds at the hot spot enhances performance because the fuel mixture will be cooler, thus denser. On the other hand, cold start warmup will be longer if there is a gap at the hot spot.

I have seen many cracked-out bolt tabs on intake manifolds where the 2 bolts go because of bending loads that occur when joined manifolds are clamped-up to a compressible exhaust gasket. Machining the manifolds as a set reduces the clamp-up loads, but not totally.

I've read posts of homemade gland rings made from seamless steel pipe. Do those need to be cut to provide end gap for thermal expansion?