Leaky Donut Exhaust Gaskets*#*##*

[Joseph K.]

Has one have trouble with leaky donut gaskets at the exhaust manifolds. I have tried lock washers, double nutting and brass nuts that seem to go on hard. After one or two rides out on the road the connection loosens and I have leaks. It happens on both sides. I have a small block and manual trans. What am I doing wrong or why is this happing. It is frustrating because the wires are located next to this connection and I can see exhaust marks in the area.
Joe

[Anthony P.]

Re: Leaky Donut Exhaust Gaskets*#*##*

When you installed the pipes to the manifold, most of the repro systems have a separate flange pipe/donut sleve that slips in side the end of the pipe and the donut slides over that. Do you have that pipe installed? I am thinking if it is not there, the donut is starting to get blown out and is making things loose.

see the attached pic.

my thoughts,
Tony

[Paul O.]

Re: Leaky Donut Exhaust Gaskets*#*##*

Joe

From what I see in your profile are you talking about your 69? If so do you have the internal extensions that are at the manifold and pipe connections? The ones that the donuts slide onto or the inner support?

Paul 18046

[Patrick H.]

Re: Leaky Donut Exhaust Gaskets*#*##*

In addition, be sure to use the "sintered metallic" donut gaskets. I had a fiber one blow apart within 50 miles last year.

Patrick

[Mike M.]

Re: Leaky Donut Exhaust Gaskets*#*##*

i use stainless steel donuts that i purchase at the local speed shop. they never blow out. i also use external tooth lockwashers next to the steel self-locking nuts i get from corvette central(which aren't configured identically to the original GM nuts) which the judges usually don't notice..mike

[Joe L.]

Re: Leaky Donut Exhaust Gaskets*#*##*

In addition, be sure to use the "sintered metallic" donut gaskets. I had a fiber one blow apart within 50 miles last year.

Patrick

Patrick------


Yup!

2" = GM #3731062

2-1/2"= GM #3768711

[Joseph K.]

Re: Leaky Donut Exhaust Gaskets*#*##*

When you installed the pipes to the manifold, most of the repro systems have a separate flange pipe/donut sleve that slips in side the end of the pipe and the donut slides over that. Do you have that pipe installed? I am thinking if it is not there, the donut is starting to get blown out and is making things loose.

see the attached pic.

my thoughts,
Tony

Anthony,
I did get a separate flange but didn't think that I needed it. I will look in the closet and check it out.

Paul,
Paul your right it is a 69 I forgot to put it in the re: line. I think your describing the same the same thing that Anthony is I will give it a try.

Patrick and Mike I will also give the Metallic donuts a try. The ones I have been using are the fiber ones. I am not sure what the self locking nuts are but I look on corvette Central. They aren't the nuts with the rubber insert are they?

Joe,

Is the metallic donut an original installation? 2" = GM #3731062

Thanks all Joe

[Patrick H.]

Re: Leaky Donut Exhaust Gaskets*#*##*

rubber inserts or nylon inserts won't last.

Paragon (and maybe CC) sell "acorn shaped" exhaust nuts that are mostly correct. They're supposed to not be easy to remove (or vibrate loose), but the orange 72 had them loosen when the owner drove it home to Chicago on Sunday. That's probably why member #14 uses lockwashers too.

I used the fiber inserts as they came with the Corvette Central exhaust system, i.e. no extra cost. Owner drove it 50 miles last summer and one of them had a hole. I replaced both (had the part numbers Joe mentions from previous, else even AutoZone has them) with metallic and no problems since.

Patrick

[Joe L.]

Re: Leaky Donut Exhaust Gaskets*#*##*

Anthony,
I did get a separate flange but didn't think that I needed it. I will look in the closet and check it out.

Paul,
Paul your right it is a 69 I forgot to put it in the re: line. I think your describing the same the same thing that Anthony is I will give it a try.

Patrick and Mike I will also give the Metallic donuts a try. The ones I have been using are the fiber ones. I am not sure what the self locking nuts are but I look on corvette Central. They aren't the nuts with the rubber insert are they?

Joe,

Is the metallic donut an original installation? 2" = GM #3731062

Thanks all Joe

Joe------


The sintered metal donut packings were not originally used on Corvettes. They were primarily used for truck applications. While not original for Corvettes, they are functionally the best thing to use.

[Joseph K.]

Re: Leaky Donut Exhaust Gaskets*#*##*

Joe------


The sintered metal donut packings were not originally used on Corvettes. They were primarily used for truck applications. While not original for Corvettes, they are functionally the best thing to use.

thanks Joe that is interesting about the truck usage

[Gene M.]

Re: Leaky Donut Exhaust Gaskets*#*##*

GM sold millions and millions of vehicles with the asbestos donut ring set up. It was used on just about everything that had wheels.

Seems to me it was never an issue back in the day ..........?

[Joe L.]

Re: Leaky Donut Exhaust Gaskets*#*##*

GM sold millions and millions of vehicles with the asbestos donut ring set up. It was used on just about everything that had wheels.

Seems to me it was never an issue back in the day ..........?

Gene------


I've always had problems with the composition-type packings loosening and leaking. It's virtually inevitable with this type packing. However, it usually results in only a chronic problem, rather than an acute problem so it does not receive attention.

After I switched to the sintered iron rings years ago my problems ended.

[Tom R.]

Re: Leaky Donut Exhaust Gaskets*#*##*

Last month I installed a complete CC N-11 2 1/2" exhaust system in my 1963 (I like the sound, I know it's not OEM) and to my surprise it had brass flanges at the donut. I used the fibre donuts supplied with the system and brass nuts with a jam brass nut and have had no problems with fit, leaks or the overall install itself. Can't say enough good things about that system and I learned most of it on this forum before I made the purchase.

[Joe L.]

Re: Leaky Donut Exhaust Gaskets*#*##*

Last month I installed a complete CC N-11 2 1/2" exhaust system in my 1963 (I like the sound, I know it's not OEM) and to my surprise it had brass flanges at the donut. I used the fibre donuts supplied with the system and brass nuts with a jam brass nut and have had no problems with fit, leaks or the overall install itself. Can't say enough good things about that system and I learned most of it on this forum before I made the purchase.

Tom-----


It takes a while for the composition packing ("donut gaskets") to "loosen", but they will. The jam nuts will not prevent this because they only prevent the nuts from backing off. That's not what usually causes the loosening. What causes it is deterioration and "shrinkage" of the packing over time and repeated heating and cooling cycles.

[Gene M.]

Re: Leaky Donut Exhaust Gaskets*#*##*

Gene------


I've always had problems with the composition-type packings loosening and leaking. It's virtually inevitable with this type packing. However, it usually results in only a chronic problem, rather than an acute problem so it does not receive attention.

After I switched to the sintered iron rings years ago my problems ended.

Joe,
I can honestly say I've had many, many GM cars with this type exhaust ring and thru thousands of miles this was not an issue.

With the limited mileage our Corvettes see today compared to the normal everyday use of the 50's, and 60's back then I can't see how this could be a problem. Perhaps restorers are not assembling correctly and using quality parts and hardware.

True the metal ring will last forever but that is not original. As in previous posts restorers are concern to have the minute smallest details correct on the exhaust system. This metal ring substitution appears to be counter productive to that interest. No different to using stainless pipes so they will not rust out.