Originally Posted by y2k600f4
I have been having some problems sealing up hedman elite headers on alum heads (SBC) after my engine rebuild. I have tried a standard paper/cardboard gasket and Mr. Gasket ultraseals (two times, two different gaskets) with no luck. They are not sealing and blowing/burning up making the gaskets unuseable. I tightened them several times with no luck (center to end). Anyway I know there is a ton of opinions on the best way including:
1. Using cheap paper/cardboard gaskets but soaking in water before installation.
2. Using double gaskests (above)
3. Putting high temp atv around the header side of the paper gasket or other types of gaskets
4. using OEM exhaust manifold gaskets
5. Felpro "blue" gaskets
6. Copper gaskets
7. Percy's dead soft aluminum
9. Metal/graphite type such as Mr. Gasket ultraseal
The header flanges don't seam warped...I just want to be seal this leak up ASAP and rather not spend a ton of $$. Is there one of these methods that is the best bet for 100% sealing ? Thanks.
Copper or aluminum gaskets are the only way to go. Doubling them is fine and sometimes useful where a little extra bed depth will help seal warped flanges. It is also important to look at the welds to insure that they don't keep the gasket from sealing. Headers move too much and too quickly as they heat and cool for ordinary gasket materials. Regardless of how straight they are when cold they want to do all sorts of Stupid Warping Tricks when hot. This is a bigger problem as the flange thickness gets under a quarter inch. The composite materials that work on cast manifolds just aren't up to the heat and movement of headers. Not to say that metal gaskets won't leak, but they usually don't blow apart when a leak develops and a simple addition to the torque of the fastener is usually enough to reseal 'em.
I had no luck with sealers being hi-temp RTV or anything else and no longer bother with them.
Also, when checking the flange and welds, do a trial fit to the engine to insure the bolt holes do not bind the bolt, having a small distance between the the fastener and the flange in all directions, allows the header to move around without getting bound up on a fastener thus forcing a warpage to take place. Something else I've found that helps, is to run a flex coupling between the collector and the head pipe. This divorces the header/engine movements from the exhaust/body movements and takes a lot of twisting moments off the header pipes that pry on the flange and its mountings. Not so much of a problem on race cars where the engine is rigidly attached to the frame but when the engine is rubber mounted it helps keep headers sealed up a lot, not bullet proof but it really reduces leaks and the time spent cinching up header bolts.
I use stainless fasteners exclusively for exhaust work. On headers I vary the head type based on the ability to get some sort of a wrench on it as it's installed. But I'm a very pragmatic builder, nothing is done because it's pretty, only stuff that's durable, reliable, and easy to get at in the pits gets used.