I've got big problems. I have aluminum PTL heads w/ straight plugs. A while back I went through a crisis of finding headers to fit them, I have no idea why they're different from any other head but anyway... After 3 sets I have one Hooker Super Comp 1-3/4($350ish) on the passengers side and a Hedman Husler 1-3/4($500ish) on the drivers side. It cost me as much as a set of custom Kooks in the end but they do fit well. After installing the gaskets that came w/ the Hedmans they promptly blew out giving me many exhaust leaks and nice black heads under the ports. So now I switched to some copper gaskets and fire it up and it's worse than before. I think the problem is that my heads are square port and both headers are more round. I think it's only leaking on the drivers side now but it's hard to tell. Any ideas on what in God's name I could do to make it shut up? Can I stack gaskets and use regular on under the copper? Obviously there aren't any other headers I've found to fit so finding some w/ more square ports would be impossible. Not to mention the expense. Any help would be greatly appreciated. Thanks.

 

Get yourself a brand new set of header gaskets, even the old fashioned "paper" kind. (Actually a composite, but I don't want to nitpick.)

Now, let me tell you what your problem is:

You install these gaskets on a cold engine, then you fire it up and you have assorted metals expanding at different rates and sideways pressure trying to blow out the gasket material.

Here's what you do:

Install the new gaskets, tighten them down so they are nice and snug, but not "cranked", start and run the engine for 5 minutes and once it's cool, do it over again.
Now, every time you go out to the car and start it over the next few days, leave 5 minutes to tighten all your header bolts. They won't all be loose, and they won't need equal tightening. Again, just snug them down so they feel tight, but aren't "cranked" down.

You'll do this MAYBE a half-dozen times. Probably half that. Then one day you'll stop finding loose bolts. At that point, you're done.
Keep the wrench around and double check every few days for a couple of weeks, but chances are you won't find any loose ones.

That's it.

 

As long as the flanges are perfectly level, you shouldn't need gaskets. Just run the red Permatex gasket maker silicone glue looking stuff. It's very high temp and I've never had any leaks. When I was using copper gaskets also, I applied it on the gaskets and never had any leaks.

Put a straight edge on the flange surface and see if it's level.

 

Try using the stock 3-pc manifold gaskets. I had a problem with constantly blowing out gaskets and tried using them..no problems since then. They only like $3 so give them a try.

 

I bought a set and put one along w/ the copper and it seals fine so far. We'll see how it does after some nitrous passes.

 

That's what I did, had the same problem, went to stock gaskets and no more blow outs..

 

O2 sensors hate silicone. Even supposed sensor safe silicone is not.