Help. I keep blowing exhaust flange gaskets

[Headrope]

Hello, Performance People. I generally post questions on the Engine board but since getting my engine running again after freshening it up - well, it's definitely more performance oriented now.

Here's my problem: I keep blowing out exhaust flange gaskets. My car is a '66. The engine is a mildly built '68 383 (.40 over 10.1 flat top pistons, Street Hemi grind Purple Shaft cam, Edelbrock Performer intake, stock heads, stock exhaust, 625 CFM Carter Competition Series carb) with a 727 automatic and 323 rear.

It seems like I'm creating too much pressure inside the pipe and the paper gasket is weaker than a cast iron manifold so - pfffft goes the gasket. But the engine isn't really all that "built" yet.

Is there such a thing as reaching a point where something other than an off-the-shelf gasket is necessary? What should I be using if so? Has anyone else run into this?

[RallyeMike]

Try the "dead soft" aluminum gaskets that are out there. The seal very well and take a beating. The exhaust on my car gets abused more than probabaly any other type of street driving or racing and sees some very high temps (I melted my shoes last year). They have held up great.

[Headrope]

I'll look for those then. Thanks.

[firefighter3931]

Percy's dead soft aluminum is what Mike is talking about. Great sealing gaskets and they're re-usable as well. Summit Racing carries them.

Ron

[CFMopar]

I use the percey's as well best gasket ever...

[Headrope]

Ha! I just returned from the parts store; they never heard of "dead soft" gaskets.
Now I know where to find them.
Thanks.

[Chryco Psycho]

copper works great too

[Headrope]

The search continues. I've yet to find any (aluminum or copper) that fits factory manifolds.

[Just 6T9 CHGR]

Now, you are saying exhaust flange correct?   The part where the pipe connects to the manifold correct?

If you are running HP manifolds make sure you are getting the correct gasket!

The HP gasket has a metal fire ring built into the gasket that should prevent the blowing out.

Also some times the mating surface isnt perfect causing a bad seal.   I have had good luck doubling up the gasket as well.

I use Fel-Pro gaskets on mine.   The part # is 60025

[charger Downunder]

My exhaust was leaking in the same spot, what i found out was my exhaust was not bolting up quare it was tight on one side and not on the other i went to an exhasut shop and got the exhaust pipe heated up and bent so it would bolt up without having a wider gap on one side.

[Headrope]

Yep - exhaust flange: the part that connects the exhaust manifold and pipe.

I do not have HP manifolds - hence the problem finding gaskets that won't blow out. I would love to run HP manifolds but haven't found any yet that will fit a first gen and are reasonably priced. High performance manifolds these days seem priced like Direct Connection posters were a few years ago: way too high.

[69fuchs]

Now, you are saying exhaust flange correct?   The part where the pipe connects to the manifold correct?

If you are running HP manifolds make sure you are getting the correct gasket!

The HP gasket has a metal fire ring built into the gasket that should prevent the blowing out.

Also some times the mating surface isnt perfect causing a bad seal.   I have had good luck doubling up the gasket as well.

I use Fel-Pro gaskets on mine.   The part # is 60025

Double them up-they will seal even if the flange on the head pipe is not perfect.

[Chryco Psycho]

Ultra Copper high heat silicone can help too

[Headrope]

So double up regular gaskets and silicon the crap out of them - got it.
I'll give it a try.

[resq302]

Prior to installing my new exhaust kit from Acurate Exhaust Ltd. I had the same problem.  Of course someone took an H pipe and modified it for my car which could have been the cause also.  Like was mentioned earlier, I doubled up on the gaskets and used some Ultra Copper silicone gasket on them it seemed to solve the problem.  Now that I have a new and correct exhaust, no problems anymore and I am using a single gasket.  What your problem could be is that your flange on your exhaust is not mating up perfectly even causing an area that is "weak" and blowing it out.