Exhaust Pipe Gasket

[Eugene V.]

I tried to replace the "donut" gasket on the right side (1970 454) between the pipe and the heat riser. I purchased a gasket from the local NAPA store and found that I could not start the nuts to the studs as there was insufficient thread available.

The height (or width) of the gasket is about 9/16". I called a number of the corvette specialty parts houses and they all said that the gaskets they sell are the same height. Is this gasket a specialty item? The studs on the manifold appear to be the correct length, does anyone know the correct length of the studs?

Thanks,

Gene

[Rich C.]

Re: Exhaust Pipe Gasket

Gene, 2 3/16" rings a bell, but as to the donut..it should be tapered on each end. By the time one side is inserted in the recess in heat riser valve-and the other in the flared section of exhaust pipe...it should only add about 1/2". How thick is the flange on exhaust pipe?

1973 LS-4 454 coupe owned 24 years
1996 LT-4 CE coupe owned 10 months
Victory Hop Devil Ale-currently on tap!

[Eugene V.]

Re: Exhaust Pipe Gasket

Rick,

2 3/16 is about what I measured, but I will check again tomorrow. The gasket height in the pipe is one measurement I did not get. If I can get the pipe to seat I will try to get that measurement tomorrow also. The flat portion of the gasket between the two bevels is about 3/8".

One more question. Do you know the thickness of the flange? Yep, I am getting desperate.

Thanks for your reply,

Gene

[Rich C.]

Re: Exhaust Pipe Gasket

Not off hand, but not very thick, some after market may be thicker. I've replaced the donut a couple of
times, I wouldn't say there was a LOT of the stud sticking through, but as I remember, I definitely had to put some effort into pushing that flange up to seat the donut squarely! No offense...but the heat riser is not upside down right? Because if it was, there wouldn't be the recess to receive the donut. Keep us posted on what you find!!!




1973 LS-4 454 coupe owned 24 years
1996 LT-4 CE coupe owned 10 months
Victory Hop Devil Ale-currently on tap!

[Eugene V.]

Re: Exhaust Pipe Gasket

Rick,

No, the heat riser is installed properly, I have made that mistake a few times in the past. The flange I have is about 3/8" thick.

Thanks again,

Gene

[Rich C.]

Re: Exhaust Pipe Gasket

Sorry...had to ask! Anyway 3/8" seems thick to me, but maybe, but I'll try to crawl underneath tomorrow night and take a peek! regards, Rich




1973 LS-4 454 coupe owned 24 years
1996 LT-4 CE coupe owned 10 months
Victory Hop Devil Ale-currently on tap!

[Eugene V.]

Re: Exhaust Pipe Gasket

Rick,

Thanks for your help,

Gene

[Eugene V.]

Re: Exhaust Pipe Gasket

Rick,

As Meatloaf used to sing, "two outta three ain't bad". I will drive it a bit tonight and let it get hot and then attempt to retighten the two nuts and hope t.hat the donut compresses with the heat. After that I got nuttin'.

Thanks again,

Gene

[Richard M.]

Re: Exhaust Pipe Gasket

I've found similar issues on the C1 exhausts I've done lately. I've remedied it by backing out the studs several threads to allow the nuts to start easier. This of course is on refinished manifolds with new studs, which I always add some anti-seize compound to keep them from rusting together.

Then after the donuts gets compressed and comfortable and the nuts are up there some more, I loosen the nuts, then bring the studs up/in more, then retighten the nuts.

Then it appears normal and is a good joint.

Rich

[Paul O.]

Re: Exhaust Pipe Gasket

Here are a few photos of an Bowtie big block left and right.

[Eugene V.]

Re: Exhaust Pipe Gasket

Paul,

Thanks for the photo, they are very helpful. After viewing the photos I can see that the right side of my car has aftermarket studs installed.

When I find a replacement manifold for the right side, I will address the studs at that time.

Thanks for your help,

Gene

[Joe R.]

Re: Exhaust Pipe Gasket

Hi Paul,

Great photos! What year is the car?

Thanks,
Joe

[Bill C.]

Re: Exhaust Pipe Gasket

FWIW ---

If you get the steel/metal version of the gasket it will never blow out and you can get a good tight fit.

Also --
be REAL sure the centering insert is in the head pipe. the gasket will slide over it and a small piece will extend past the edge and fit into the heat riser.
The NOS pipes had this piece spot welded to the pipe.
Aftermarket ones do not.

[Paul O.]

Re: Exhaust Pipe Gasket

Hi Paul,

Great photos! What year is the car?

Thanks,
Joe

1972 big block automatic.