87kevroc

Recently I had the engine in my 87 IROC 350 rebuilt. The mechanic that installed the engine installed exhaust manifold gaskets. I am now working with another mechanic.

A leak developed between the manifold and exhaust ports, making the engine sound bad, especially when accellerating. So I took it to my new mechanic; he removed the exhaust manifold gasket on the passenger side and put the manifold back on without a gasket, which fixed the problem. The engine sounds fine now.

I was under the impression an exhaust manifold gasket was necessary to provide a good seal, the mechanic says it's not. Is he right? Don't they have gaskets from the factory?

Kevin91Z

iTrader: (1)

No they dont have gaskets from the factory. I know you need gaskets for headers, but I've never put gaskets on factory manifolds.

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ViciousZ

iTrader: (1)

I had the opposite problem with mine. After the engine was worked on, I had an exhaust leak because the mechanic didn't put a gasket in. So I took it to another mechanic who put a gasket in and the problem was solved. Much later when I installed my headers, I discovered that on the side that hadn't leaked the bolts were only in finger tight. In fact, I took the exhaust bolts out with my fingers! The first mechanic obviously didn't tighten/retighten the bolts. So it's possible that it wouldn't have leaked even without a gasket if the bolts had been tight. Anyway, it was my understanding that engines didn't come with exhaust gaskets from the factory, but that you might need them later if either surface on the head or manifold was warped at all. My advice is do whatever works to keep it from leaking.

Engineboy

On Chevy and *(cough)*Ford..*(cough)* small and big blocks you don't need a gasket unless there are surface imperfections you want to seal.

This is my rule of thumb when doing ex. (not that its right )

I surface every manifold that comes off the car. Period. Alot of manifolds will warp when you take them off the engine and then the surface isn't flat anymore. Putting a gasket in there will cure the leaks but will eventually, through heat expansion,wear out. Then you need to put another one in there.

On most engines I install (the V8s and V6s) I surface and use no gasket. I don't have any problem with ex. leaks.
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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
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GO #3

[This message has been edited by Engineboy (edited December 07, 2000).]

[This message has been edited by Engineboy (edited December 07, 2000).]

Pat Hall

iTrader: (31)

My suggestion would be if you're not going to use gaskets, I usually put a thin layer of permatex "right stuff" sealer on the flange before I install it so it will seal any minor surface imperfections. I do the same thing where the collector bolts up the bottom of the exhaust manifold. This method has worked great for me so far(knock on wood).



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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

87kevroc

Thanks for the response. It's good to know my mechanic was correct.