I'm going to get more specific. Most header gaskets will work if the surfaces are completely flat and the bolts don't back out. If the flange is warped and/or a bolt backs out, anything other than solid metal will burn through. The result is that you will be replacing the gasket. I currently run a felpro 1406 on the driver's side and a percy's on the passenger side. The reason obvoiusly is that a bolt backed out and toasted the 1406. Of couse it toasted the dreaded passenger side. So there is a rolling test bed where they both work. I'm still eventually going to replace the 1406 on the driver's side, but for now as long as it doesn't leak it can stay for a season. It's your call as to what to use. I should have used Percy's the first time and I ended up regretting saving a few dollars.

 

Which percys gasket are you running?
Copper, Aluminum other?

 

Percy's Seal-4-Good "dead soft" aluminum. Part #66031 For D-port LT-1's.

 

Me too

 

Yup, you can pick up Mr. Gasket header gaskets at Autozone for right at $20.00.

 

I have those. Headers are going on tomorrow, I'll let you know how it goes.

 

I do not use exhaust/header gaskets.

High-temp RTV has worked for me over 25+ years with no leaks.

 

The Mr.Gasket Ultra-Seals should be fine. Don't spend money on hype. Actually, the stock GM gaskets are excellent. The "copper" and "aluminum" guys... I dunno.. I think it's a scam.

I'm running Exotic Muscle headers with Mr.Gasket Ultra-Seals and Breslin header bolts. A "one time" install and zero problems.

 

How is it a scam? I would rather spend $40 one time on header gaskets and be able to reuse them. That and i used them once before and they worked great. I don't have any problem using other gaskets because they all do there job, and certain ones require more maintenance..like the paper gaskets, if they start to leak they usually burn the gaskets up....this is difficult because you have to scrape the surface when you replace them. The copper and aluminum ones pull right out, I like them for that reason as well. I also don't use breslin or stage 8 locking hardware because i don't deam them necessary....I keep my header bolts tight as regular maintenance.

 

Don't get the Percy's if you are running stock exhaust manifolds, they won't line up right so there is no way they'll seal. They may work great for headers though, I suspect thats what those who recommend Percy's are using.
Felpro's should be fine. They're easy to get and inexpensive. For stock setup no need to get fancy and spend any extra $.
Also, don't use any RTV on the gaskets. RTV is only rated to around 650deg. Those manifolds can get much hotter than that and turn the RTV to powder. I tried it once, it does not have a longterm benefit as it doesn't last.