Exhaust Manifold Gasket Leak / Burn through

[firenguitar303]

Hi All,

I've replaced the stock exhaust manifold with the 4-2-1 manifold from IAP on my 1977 Fiat Spider. I definitely had problems when I first did it with the bolts loosening up, which burned out the manifold gasket in different locations across 3 of the cylinders. I disassembled it, cleaned everything up and reassembled with a new gasket. Everything was fine and snug, i re-tightened a few times over the first couple days. It lasted about 2 weeks and now it's burned through on 2 cylinders again. The bolts still seem all nice an snug. I've got one more exhaust manifold gasket (I got two the last order), is there something I'm overlooking? Should I try a product like Permatex 1372 in addition to the new gasket? Or is there something else?

Again, I thank everyone for their input.

Curt

[So Cal Mark]

I'd check the flange for flatness. Constant loosening is an indication the flange may be too thin and warps when hot, or you may have worn threads on the studs

[firenguitar303]

They don't seem to have loosened again. I checked them and they're all tight, so I don't think there's anything wrong there. I checked when i had it apart and all seemed smooth and burr-free. I was wondering if there was a "flatness" issue, could I use the Permatex product to fill the gaps?

[So Cal Mark]

there shouldn't be gaps at the flange

[Kevin1]

could I use the Permatex product to fill the gaps?

Sounds like you found the problem. If the face isn't flat it won't clamp down evenly on the gasket. Check it with a straightedge. If the flange is heavy enough it can be ground flat, but if it is too thin it could warp again when they get hot.