Inliners International Forums General Discussion Hi Performance Offy intake manifold question

I plan on putting an Offy 4 barrel intake on my 250 and just wondering about the expansion difference since it is aluminum. Is there an issue with the sealing of the gasket or torque specs to manage the aluminum expanding and contracting?

YES.
I saw it a lot while swapping intakes with used gaskets for testing. The best idle ironically would be cold (even with choke off). After the engine warmed up, the constraints of the block, iron exhaust, and alum intake often led to small leaks and a rough idle when warmed up.

I think U need a new gasket and a perfectly flat seal then it's ok.
And, replace the locator pins on each end with real studs or bolts, that helps too.

OK great, thanks I will see about getting the manifolds surfaced flat. thanks for the feedback.

Flat obviously is correct, but I moved away from using gaskets at all for most things, instead using Permatex "Right Stuff". Very strange stuff, it's not a silicone, exactly, it grips metal and is much tougher. I've assembled two engines with it, the last one my Rambler six, the only gaskets in the engine are headgasket and the reusable valve cover "O-ring", everything else Right Stuff. ZERO leaks. ZERO.

Specifically analogous to your app, I used Right Stuff on a 1970 AMC 232 six with a 1981 aluminum intake. Worked and lasted years (sold the car).

In fact the earlier cast iron intakes warped and leaked regularly. You'd think the aluminums would be worse, but I think the inherent flexibility of the aluminum meant that it could stretch and shrink without permanent deformation. in any case there's been no systematic problems with the very common iron head/aluminum intake on AMC sixes. (The factory aluminum manifolds are quite good.)

How well does it clean up after its been baked on?