Exhaust manifold

[Willis76]

I noticed that I have a small exhaust manifold leak at the block. It seems that all it may need is to be snugged up a bit.

Is it better to snug this up it when the engine is warm or cold? Any precautions one way or the other?

Getting very tired of this long winter - thanks

 

[Bob Chadwick]

I can't answer your question specifically but found that when I had a small exhaust leak that they took the manifold off, planed it and then put it back in place with a gasket. No more exhaust leak.

Bob

 

[78SilvAnniv]

exhaust leak

Here is my thought on the matter.
If you have an exhaust leak and can hear it, it has already deteriorated the gasket where the leak is coming from and I don't think tightening it will be a cure.
It could possibly be a temporary fix if you have caught it before it has become too large...but I think that if you can hear it, it is already too large.
I also think the best course of action would be to replace the gasket as bobchad stated.
Heidi

 

[pmwild]

The small block chevy is infamous for warping manifolds due to shrinkage. I would remove the manifold and inspect it. Pay particular attension when removing the exhaust bolts from manifold to head. If they are tight and dragging when trying to remove them I would strongly recommend replacing the manifold. What happens is the manifold mounting bolts won't all want to go in. They make a tool that spreads the manifold to install it but when the tool is removed pressure goes back onto the bolts and sooner or later they tend to snap.

 

[Willis76]

Thanks

Thank you all - seems with more snow on the way, I should have more time to make the reapir.

Thanks again

 

[JohnZ]

Chevy exhaust manifolds don't use gaskets - they bolt up solid to the heads. If the plane of the attaching surface on the manifolds is flat, they won't leak. Pull them off and have them checked for flatness, and planed if necessary. Remove the bolts carefully, and when you re-install them, use anti-seize on the threads so you get accurate torque results and they'll be easier to remove next time. I've been building small-block Chevys for 40+ years, and never heard of "spreading" the manifolds; if the manifold holes don't line up with the holes in the heads, trash them and buy another set.

 

[78SilvAnniv]

Oops!

Chevy exhaust manifolds don't use gaskets - they bolt up solid to the heads.

I must have been thinking about the headers I had a looong time ago...
Heidi

 

[Dave L.]

Speaking of warped exhaust manifolds... A customer I sold an engine to several years ago called me and said "you sold me the wrong engine,my exhaust manifolds don't fit the new engine". I tried to explain to him he had warped manifolds and would have to replace them,he was hard to convince since he said they fit his 'old' engine. Actually,I have run into this problem many times. Like John said,trash'em and buy new ones.

Dave

 

[Mike Carter]

I'm a little mixed on this one. I agree tightening won't necessarily cure your problem not with stock manifolds, I agree you need to plane and ensure flat. But there are applications of SBC that use gaskets, and I can't remember buying a gasket set that didn't have exhaust manifold gaskets in it. I think you can put gaskets in it and alleviate some problems, however if manifolds are warped or craked gaskets won't fix. My 2c.

 

[Willis76]

thank you all - this is certainly a great place for all types of information. I can't imagine what I'd do if the internet just suddenly went away - like Baghdad TV.

thaks again -

 

[JohnZ]

SBC's with cast iron exhaust manifolds (including all Corvettes through 1979) didn't use any gaskets, although every gasket set on earth includes them, apparently to make people feel better The manifolds were fabricated tubular stainless from 1980-on, don't know about those - never worked on one that "new"