Intake manifold vacuum leak

[steve from staten island]

My brake issues when i converted to front discs were a to large a piston in master, thanks to Cass at Dr Diff i went with a dual diaphragm booster and a 15/16 bore master. This improved braking. However it could have been better and we felt low engine vacuum 12" was affecting the booster.
The car ran a little rough at idle, the Vac gauge showed 12 and sung back and forth a few degrees. The problem was a valley gasket and no gasket that i used no silicone on. With gaskets and pan the intake manifold will not mate up. So i used a new pan and a good silicone gasket maker. I let it sit for a day or so before starting
What i didn't understand was my high temps at the tailpipe. When i put the rubber hose over the pipe to vent gasses outside , the hose would get to hot to touch.
That should have been a tip off. Now with a over lean condition that hose gets warm at the most. Combustion temps are clearly lower, so we know there was a good vacuum leak.
I now have a almost steady needle on vac gauge and 15-16 inches of vacuum.
What bothers me is the fit of manifold to head and the fact i cant use any gaskets other than the valley pan. Could the heads have been resurfaced to many times over the years. Do i need to resurface the intake manifold mating surfaces. I certainly had a vac leak and certainly have improved that condition. Any thoughts?

 

[65wgn440]

You didn't say if your pedal feel improved after gasket replacement, but sounds like you have it sealed now, so why worry ? You could always check the intake ports externally with propane and tachometer, and keep an eye on plugs for signs of oil consumption if you still suspect sealing issues. I remember somebody used to sell pans with very thin paper gaskets integral, or could be hy-tacked on, if needed, to help seal ports.

 

[Fran Blacker]

If you take manifold off again clean both surfaces, heads and intake. Put something like dry or wet marker or dykem blue on head manifold surface. Place manifold on and rub a little back and forth, remove manifold to see how its mating.