How to seal exhaust leak between manifold and head?

[CharlesElliott]

My manifold on my race car has always leaked a little on the cylinders at each end where it joins the head - this is obvious from the soot marks on the gasket where it blows by the gasket sealing rings. I used to use OEM gaskets, and switched to aftermarket ones to see if it made any difference but it doesn't.

Looking at the manifold, there is a chamfer that is probably a little too agressive and therefore failing to make a good seal.

Apart from a new manifold, is there anything else I could do? Could I smear a little exhaust putty on the manifold to help seal it? Or is that a really bad idea?

[Paul Richards]

Silicon sealant will do the job. 

[CharlesElliott]

Thanks Paul - I assumed it wouldn't be up to the temperatures involved?

[Nigel Riches]

First thing check if the manifold face is true, they do distort, if it's out of true there may be enough material to machine it back, check also at the cylinder head face, not so likely here as there is more metal heat and cool. 

Make sure the two faces are free from any foreign object debris which would preclude a flush fit, ie, old gasket material or sealant. 

Don't be over exuberant on the fasteners, and torque progressively to the figure for your engine. 

Regards, Nigel. 

[Roger Ford]

Surely you have a spare manifold to try a different one? If not, I've got two of them.

[CharlesElliott]

I do have a spare one, but that might risk losing a few bhp 

[Roger Ford]

Good point - it wouldn't have the fittings for the turbo.

Maybe the leakage is what's giving you that ginormous horsepower.

[Mankee]

Sod the tuned exhaust; just introduce an air-leak!

I'd get the manifold faced to start with.