Replacing exhaust manifold gaskets

[Bills money pit]

I have a exhaust manifold leak which can be heard when accelarating. I intend to replace the gaskets and upon trying to loosen the stud nuts, they are rusted to the bolts as one. Any ideas on how to loosen each one without breaking them off. Thanks for the help.
Bill...

 

[fine69]

Try saturating it with PB Blaster penetrating oil. I would spray the bolts several times within a 36 hours period... hopefully that will help unfreeze the nuts.

 

[BarryK]

stock exhaust manifolds don't have gaskets to replace........

 

[Bills money pit]

what type of sealer will stop the leak?

 

[BarryK]

are you sure the exhaust leak is coming from where the exhaust manifold mates to the head? More likely is that it may be coming from one of the A.I.R. pipe connections in the manifold or elsewhere as the stock manifold is pretty thick and not very prone to warping on the mounting surface. If you are positive that is the location of the leak a local machine shop should be able to mill the manifold true for you.
I've never looked so don't really know if anyone offers a gasket for a stock manifold. Using a gasket solely to help "seal" a leak where a gasket was never originally intended to be you are using a bandaid approach to solving the problem rather than doing it correctly.

 

[Vetsvette2002]

I have a exhaust manifold leak which can be heard when accelarating. I intend to replace the gaskets and upon trying to loosen the stud nuts, they are rusted to the bolts as one. Any ideas on how to loosen each one without breaking them off. Thanks for the help.
Bill...

Unless you are refering to the 2" dia. round gaskets, there were NO gaskets used between the exhaust manifold and the cylinder head.

To replace the 2" donut gaskets, apply either PB Blaster or Kroil and allow time to penetrate. Then try tightening first, another application of penetrant then loosen and remove the 3 front exhaust pipe to exhaust manifold retaining nuts.
Remove old gaskets and replace with new ones.
Re-install the retaining nuts and torque to spec (called out in the AIM).

Don

 

[Bills money pit]

Thanks for the replys. Now I am not sure where the leak is located. A mechanic friend told me it was the manifold gaskets. Apparently he did not know there we no gaskets between the manifold and head. The leak is minor as I only hear it when I give it the gas and then it is faint. Maybe I should just turn up the radio and leave it alone. I always want the car to be perfect. It is that kind of vette, as orginal as any I have seen around these parts.

 

[red70vette]

I would be wary of advice from your mechanic who thinks there is an exhaust manifold gasket leak when there is no manifold gasket. It tells me that he is like many other mechanics who are parts changers and have no diagnostic skills. They will continue to change parts until they get it fixed or you run out of money whichever comes first.

 

[bradfordsvettes]

there are gaskets out there you can use .From the factory no gaskets were used but over time and with exhaust leaks ,rust etc :ugha gasket may be a band-aid for an irregular surface I have used the aluminum and copper with good results they are one piece the paper and metal ones do not hold up . At best it is still a stop gap repair hnoes Steve

 

[Bob Chadwick]

there are gaskets out there you can use .From the factory no gaskets were used but over time and with exhaust leaks ,rust etc :ugha gasket may be a band-aid for an irregular surface I have used the aluminum and copper with good results they are one piece the paper and metal ones do not hold up . At best it is still a stop gap repair hnoes Steve

X2. There were no gaskets there to start with, though they are commonly used to repair a leak. I had a leak problem with my exhaust manifolds, before headers, and one was solved at the metal shop and the other still required a gasket.

 

[daveintexas]

There is also the possibilty that the manifold could have a small crack, and THAT is where you hear the leak coming from. They are made of cast iron, however they DO crack! Check on the bottom side or even on the inside next to the engine and see if maybe it has a very small crack in it.

 

[bill81vette]

I too had an exhaust leak but only when I started the vette,after a few minutes it would go away.Last winter I found the leak to be where the exhaust pipe meet the manifold on the right side.there is a valve there for the emissions.I could take the flange and wiggle it when the engine was cold.:eek
so under the vette I go with a socket and a ratchet and proceeded to break all three studs,even though I had used PB for a few days prior,off comes the manifold,drilled tapped and replaced all three with new studs and nuts.
put it back together and found the other side had a slight leak as well!!!:ugh:ugh
prepared to break those three but got lucky and the tightened right up without breaking
I did put new manifold gaskets on the right side.
and no more leaks!!

 

[dirtypants]

exhaust manifolds 1981 gaskets or not...and to all who have an 81

bill81vette;
\Hi..saw this ol thread..so first off..I have exhaust leaks..either small cracks in manifold or at mating surface to head so will take em off an see whats up..this on my 81 4 speed..by the way Bill also metallic dark blue. so..hoping the manifolds come off ok..and I will check em out but also have a used spare set that I will check..see which are the better..suppose I will have the mating surface milled flat. Help..confused...in 1981 with the stock orig tube type manifold..not the cast as was used prior to 81...still no gaskets??
and hey..we need an 81 forum or such..as the 81 has its own set of "stuff"...such as the one year computer, one year distributor, these basically one year manifolds and things like this and related parts not listed/carried at the major C3 suppliers. Glad there is ebay.
thanks
Nick

 

[Antz81]

and hey..we need an 81 forum or such..as the 81 has its own set of "stuff"...such as the one year computer, one year distributor, these basically one year manifolds and things like this and related parts not listed/carried at the major C3 suppliers. Glad there is ebay.
thanks
Nick

If you look in c3 general discussion you'll see a sub forum for the L81 vettes like ours. The distributor continued for a while after the 81 though.

 

[SVO]

As noted, there is no gasket between the head and the exhaust manifold. But Fel Pro and Victor Reinz both offer a gasket for that location. Fel Pro part number is MS9275B. Victor Reinz part number is 95090SG or 95094SG.

My favorite rusty nut soak is Kroil. I would recommend that before attempting to loosen the stud nuts that you wire brush the studs to remove as much rust as possible. Use a thread chaser to clean the threads below the nuts and then soak with your favorite penetrating oil. Even with all of that, you still run the risk of breaking a stud. If you end up replacing the studs, I recommend using a standard steel stud with brass nuts and not a stainless steel stud. If in the future, you twist off a stainless stud, then it will probably be a momma dog to replace. Use of brass nuts will ease future removal.

Good luck with your exhaust leak repair.

 

[Tom Bryant]

We have been trying for years to get members to post their 1981 specific posts in the L81 Forum but it's been an uphill battle. We used to have a very active group of '81 members but some have passed on and other '81 owners either just don't use it or prefer to use the regular C3 forums. There is so much different on these cars that many times accurate answers don't get posted to questions in the regular forums. We really need to start using it more before it goes away.

On topic. As I said in your other post iron manifolds don't use a gasket to the head. Beginning in 1981 when the tubular manifolds arrived they did use a gasket. The surface is too irregular to ever seal without one. You don't need to get the surface milled. The gaskets will do the job. I replaced the AIR check valves about 10 years ago or more and had to remove the manifolds to get heat on them. The valves weren't going to budge without it. I got the Victor Reinz gaskets listed for 1981 from NAPA and I haven't had a leak since. I never had a leak with the GM gaskets before either but you must use the proper gasket with the tube manifolds.

I agree with the standard steel studs and the brass nuts. It's the best way to go. GM Parts has been selling the brass nuts for years as the service parts for these. If soaking them doesn't get them to loosen heat them cherry red then spray them with penetrating oil to quench them. This will usually break the rust bond. Also try to turn the nut both ways to break it loose. When removing it, If it stops turning spray more penetrant above it and re-tighten it a few turns to clear the debris out of the threads. Then spray below the nut and loosen it again.

Of course, if you are not going to re-use these manifolds you could just make quick work out of it by twisting off the studs.

Tom

 

[dirtypants]

Bills 2007 post about 81 exhaust manifold and gasket

so..for a 1981..exhaust manifold gasket or not?
There are conflicting posts. For sure the manifold part changed in 1981 to the tubular type, GM # 14022625-W and 14022626-W, having emission tubes and A.I.R vertical pipe. Please fact check me on those #s, and also if 2 inch outlet. Some say that in 81 a factory gasket was used, so true or false and if used what type, and part #..one piece or individual port.? From observation and various posts, it seems that a gasket could be used, no harm done (but still a milled flat manifold is the no leak key) , and that in any consideration of an aftermarket header, clearance for spark plugs and clearance to std trans cross shaft, and bracket for A/C condenser must be considered. It does seem a good idea to have the manifold mating surface milled to perfect flat..whether prior year no gasket..or not. In 81 the heat riser changed as well. Some like brass nuts on the flange, some recommend Stover lock nuts. Manifold torque is 35 ft lb.
OK,,now a bit of a rant: There is a lot to getting any power or torque gains from exhaust..headers alone won't do it until the rest of the exhaust also is improved. Modern exhaust theory and equipment is a lot different than it used to be..with free flow mufflers, X cross over for improved pulse scavenging, mandrel bent tubing. Then there is getting more and colder air going in..and then tuning for that. For motorcycles it is quite important..a few HP or change in torque coming on ..IMHO for your car, unless a modified engine or racing..it is more looks, psychological.and of course the sound. I kinda agree with the old hotly debated thread about headers, that if HP and torque were that easy to get by adding a slick looking header then why would not all car manufacturers do it. If you are making hundreds of thousands of em cost would not be the issue. That said there are plenty of dyno tests showing a complete, header to tail pipe, improved tuned exhaust will get you 10 or so HP..and it looks cool..which brings up..again..get cool air into the engine. Thanks for hangin in
Nick

 

[Tom Bryant]

We must have been posting at the same time. Here are the gaskets you need for stock tubular manifolds. You do not need to mill the manifolds.

Gaskets

1981 manifolds have a 2 inch outlet. They went to 2 1/2 inch in 1982. Use brass nuts if you want to be able to easily remove them in the future, period. This and the information in the posts before your post above is not opinion, it is fact.

Tom

 

[dirtypants]

got it..thanks..re gaskets for 81. Since 81 exh manifolds seem a bit rare I will keep my take offs which may be good enough to repair and would be a good model for someone building up headers from scratch.
and..my comment on conflicting..not you..but there are posts on threads..from well meaning ..that say no gaskets ..not realizing the change in 81.
Things live on on forums and the web..so I try hard not to post something I have not fact checked, often listing the source for the "fact". no reason for anyone to believe me..just another ol codger..unless I can verify my info. I am new with 81 vettes..and don't even have the resources to check myself yet..so thanks again. Yes I will use the 81 sub forum..and just have.
Nick
near Spokane WA
81 dark blue met, 4 spd