I'm just beginning the final assembly of a 327 for a Z conversion. I have a set of 461 double-hump heads that have been nicely ported and polished. Looking closely (I guess for the first time!), I noticed that the walls that divide the intake ports (both front and rear) have been worked to the point that they're quite a bit thinner than a standard manifold gasket. As a matter of fact, they're about 1/16th of an inch! A standard Fel-Pro gasket I had lying around measures a little less than 1/4", though the raised center section of the gasket is about the same width as the wall. Until now, I hadn't thought about it, but with the standard gasket I'm going to have big old barn doors in the intake stream. I guess I could trim a standard gasket down with a Dremel tool or something, matching them to the runners, but that seems like a recipe for vacuum leaks. I'd hate to trash the heads - somebody obviously put a great deal of work into them, they're beautiful. Any suggestions? Are gaskets with super-narrow rails available, or could I modify a conventional gasket? Perhaps metallic ones that could be matched more easily?

 

Hey now you have an excuse to throw those stock crap heads away and pick up some Darts which, by the way, will outflow those modified double humpers right out of the box. Better yet keep em as tokens of bad machining...

Port or Gasket Matching means just that...

Machining 101:
The ports are opened up to the inside dimension on the gasket set being used. Traditionally the surface of the object being ported is sprayed with machinist dye and the gaskets are taped on in their respective location(s). The outlines of the areas to be ported are then scribed onto the object based on the inside dimensions of the gasket.

From what you describe, it sounds like this didn't happen here. the heads will never seal right without enough gasket material. Unless you can find the set of gaskets that were used for the templates to set up the porting work, you can thank whoever for making you a set of garbage... Someone got carried away with the Dremel...

btw flow bench testing has shown that there is not much gain from port matching heads. Yeah it looks cool but unless your a bracket/pro racer trying to extract every cfm out of the heads its a big waste of time/money Your money is better spent in pocket porting/bowl blending and good 5 angle valve job.