Den14

I have a leak where the exhaust manifold and cat come together on the passenger side. Is there a gasket that goes in between the two? It is a stock LT-1, 1992. If there is a gasket, where can I find one? Thanks Forum!

JMelton

Are you sure it's leaking there? My 96 LT1 was leaking and the muffler shop I took it to said the same thing.. It was a CRACKED exhaust manifold that was causing it, which is why mine has Pacesetter Shorty Headers on it now.

Den14

I am fairly sure that it is leaking from that joint. Is there a gasket that can be replaced?

WVZR-1

There is NOT a gasket/seal in that location. It's a ball/socket metal to metal seal. You can remove them and clean both of the sealing surfaces and use new studs/nuts to correct the seal. The studs can be tough!

They need soaked for a couple or more days before you attempt the repair

Good luck - it could get nasty!

Den14

Thanks for the info and advice! Hope for the best, prepare for the worst!

JMelton

The Muffler Shop I took mine to was pretty sure it was that flange too.

Both Donuts were there and intact when I took everything apart to put the headers on. Once we cut the heat shields off of the right side, we saw what was making all the racket. Cracked almost 360 degrees, and a chunk floating in and out of a crack hole.

Den14

Yikes! I may be going with headers in the future anyway, but I hope it is just the joint at this point!

mcm95403

Sorry, but there IS a donut gasket on the LT-1's. The L-98's have the donut shaped into the header. I used donuts for an LS-1 Corvette on mine (found out they fit since I had a spare) that I HAD to get from GM. The aftermarket versions don't have the "teeth" required for retention in the bottom of the manifold, so they keep falling out when you do the install. The GM ones have the teeth and stay put while you bolt up the pipes. About $22 from GM per each donut which was $1 more than the big box stores.

WVZR-1

OP mentions having a '92 and the sealing system you had in your image was first used in '96 BUT the later manifolds were used to service all year LT1's and THEN the donut you show HAD TO BE USED! I don't believe you'll see it used on a '95 or earlier unless the manifolds have been replaced.

I believe the "cross section" views in the FSM indicate this arrangement in the '92 car. The OP can post back with what he finds and maybe a manifold casting number. Do you have what you feel are LT1 manifolds hanging around with some casting information?

toptechx6

I just looked at the manifolds that came off my 93, there is no gasket used, it is the cast in place ball and socket arrangement.
I could not find any casting numbers, but they may be under the tin heat shields that are riveted to the manifolds.

WVZR-1

How have you been?

That's what I would have expected to find and it's good to have it confirmed. That's the way I believe it should be through '95 production. The heat-shields are pretty good sized best I recall so the casting is likely well hidden.

tilac999

Just to clarify, does the L98 use a gasket or is it just metal to metal ball and socket? I've got a leak. Thanks.

WVZR-1

Your L98 should be ball/socket with no seal!

Den14

So...If there is a leak at the joint, can a donut be used to help the seal? Would a GM dealer have the part then?

WVZR-1

If your manifolds are original there is NO SERVICE PART - if it is a service manifold then yes a dealer will have them. A service number for them used to be 15713154 but I expect that will change. That is for sure the least expensive part number. Start with that one if you need a seal and have a manifold that has been replaced. You might buy the GM studs and nuts also. They're generally of a better quality than the after-market but might be expensive. The material used is different and meant for exhaust applications.

mcm95403

I stand corrected!

prostreeter

is there a donut here on 92 lt1 or not.

prostreeter

after reading all treads zip corvette sells a donut for lt1 fel pro #61258 so should i need or is it just matched metal to metal, thanks if you can tell me. 92 vette

WVZR-1

If your manifolds are "original" there will be NO seal. If they've been replaced then it's possible that there's a seal present. If there's a seal you won't need ZIP, a GM dealer in your area OR the "local" auto parts jobber in the area should be able to help.