Jmccreary

I have a 80 C3 that has an exhaust leak at the manifolds. I decided that since repairing the manifold leak I would detail the engine compartment at the same time. I finished removing everything last night and found there was not gaskets on the exhaust manifold to block seal. It was metal to metal. Is that normal? Also, there is no gasket between the manifold and the heat riser valve. Should I install a gasket in this location? I just want to make sure that everything is sealed since it is such a job getting the exhaust manifolds off the engine.

Also, at the back of the block there are two brackets for the spark plug wires. I have been trying to find the rubber grommet that goes in the bracket to hold the spark plug wire, but cannot find a supply that has them. Anyone know who would have these.

Thanks
John

Crash80

Been there with my '80 C# as well. I kept having an exhaust leak around #6 and #8. You should have gaskets, I have read some people saying there aren't suppose to be any but I think that is wrong. I have never heard of an old Chevy 350 that did not leak with out ewxhaust gaskets. I would get the Felpro one piece gasket instead of the little donut type. They are easier to install and last longer. I aslo had the heat riser issue. There should be a gasket there as well. I just has mine fixed last week at Midas as I didn't have time to deal with it myself. The gasket was not even there according to the guy who fixed it.

As for your spark plug retainers, I see Ecklers has some in their catalog for a 68-74 Vette on page 304 of the catalog. Give them a call, I am sure they have them for an 80, heck it may be the same part.

Best of luck

CVT4ME :cheers:

mvftw

Gasket were NOT used from the factory. I've been told to use Permatex Copper Only (high heat) and Not to put on gaskets. I'm having my exhuast redone and I'm taking off the heat riser and going right to the manifold (true dual, no cat). I'm also looking for the spark plug grommet.

Jmccreary

I suspected that there were no gaskets from the factory because it looked as thought the manifolds had never been removed. So should I use the high heat copper on the heat riser seal also, or just the manifolds?

mvftw

I would put it on both. It's just to make up for wear on the surface.

Crash80

I am not sure that you would be able to tell if your manifolds have ever been off just by looking. Mine are totally stock and I can't tell mine have been off, though I know they have. I am not trying to be argumentative here, but I don't see what would make a Corvette 350 of this era exempt from gaskets. It is not as if the heads were of any great caliber from the factory. I am not sure that a stock Chevy 350 out of a Vette would have been much different from a stock Chevy 350 out of, say a Camaro, which I think had exhaust manifold gaskets. I know my '79 Z-28 did. Anyway.....I digress. I don't know if they make a gasket out of copper for the heat riser or not so I can't help you much there. If they do, I would consider getting it. I know if I pop one more exhaust leak at the heat riser, I am going to have it removed as well. That is the one thing I have been battling on this car continually. As of now, I am winning that battle but the war rages on. Oh the joys of owning an old Corvette!

CVT4ME

BSeery

The factory did not put gaskets on the stock exhaust manifolds. I have the Assembly Instruction Manual, which lists in detail EVERY part put on the car. It even lists where to put things like sealant or glue and how much to use.
My father worked for Chevy as a mechanic when the C3's were out and he also confirmed that they did not use gaskets on the cast iron manifolds or the stainless steel tube manifolds they used from 1981 and on. I am pretty sure that none of the current GM cars use gaskets now either.

As far as a leak, yeah, try some high heat RTV. Also check that it's not leaking around the A.I.R pipes or the exhaust "donut" gasket at the connection to the pipe.

BSeery

I could not find any rubber gaskets so I took them off and found the plastic / rubber dip that is sold for tool handles. It comes in a can, can be found in different colors. Clean the part really well, and even scuff it up a little. Dip it in the plastic coat and let it dry. Works fine but is not factory correct. For thicker coatings, dip repeatedly

Jmccreary

Here is why I feel the manifolds had never been removed. All the stock french locks were on securly in place, even thought they had degraded significantly. Now who would take the time to install french locks, which are stock and generally no reusable, but not install manifold gaskets.

Where is the heat riser leaking from? The top? That is what I am concerned about. There is not much surface area between the manifold and the heat riser. I have seen the early 70's heat riser gaskets, but I am not sure they would fit the 80.

Crash80

I see your point. You are probably correct then. Alright, I admit I was wrong, I am just having a hard time wrapping my head around the gasketless exhaust, sounds like a recipe for a leak to me.

Seems that my leak was on the top side of the heat riser, but I can't be sure. The way the guy listened for it was using a cut up piece of garden hose, about five feet long, that he would move around the suspect areas. He listened through the hose to isolate where the leak was. He let me listen as well and it seemed to work pretty well. I did not look up to see where he was holding his end unfortunately but it seems that I remember him saying that the gasket where the heat riser met the manifold was gone. Maybe you could see if Midas would let you see what that gasket looks like, or maybe sell you one if you are doing all your own work.

Sorry if I ruffled anyones feathers with the manifold gasket talk, it was not my intention, I was more or less just typing out loud.

Best of luck.

CVT4ME

mvftw

No offense taken...live & learn...that's what this forum is for.

Fevre

Get a good set of gaskets, easier to remove than having to scrape off the hi temp stuff when you need to work on them. I used the metal Felpro ones that come in sets where there is 3 small gaskets per side where the middle two ports where one gasket. They are nice because they are hooked shape so you can start your bolts then just drop the gaskets in. If you burn one up you just undo the bolts far enough to get the gasket out and drop a new one in with having to pull all the bolts fully out of the head.

Kevin_73

I kept having weekly exhaust leaks from the both of the head to manifold joints. After going through several different types of sealer and different gaskets I finally replaced the manifold bolts and it has stayed sealed for the last 3 years :hurray:

I also had repeated problems with the doughnut seal at the heat riser. I finally found out that there was a solid metal doughnut available to replace the composite one. No problems since I put that in either. :auto:

Jmccreary

Thanks for all the help. My feathers didn't get ruffled...I don't even have feathers. I think I am going to go with the fel-pro gaskets just to simplfy installation. The metal size goes towards the block...right?

One point on the wire looms. Ecklers stock them. I ordered a set and when they came they were the standard GM looms that slip on the top of a valve cover bolt. Not even close to the part I'm looking for. I guess I might check the local corvette salvage yard.

J

Crash80

In Ecklers catalog No. 203, page 304 there is a drawing of the spark plug bracketing for a 68-74, which looks like similar to my '80. Is #5 the part you are looking for? there is a drawing in the left colum in the middle of the trhee figures on that page. Maybe I am not understanding what you are looking for.

I am like you, I am going with the Felpro next time as well. It was recommended by some other Vette guys here in the area. I believe the copper side goes in toward the block.

CVT4ME