Cometic MLS Exhaust Manifold Gasket C4151-030 - B-Series

Cometic MLS Exhaust Manifold Gasket for B-Series - Part #C4151-030

A ticking exhaust leak at the header flange on a B-series is annoying at idle and a real problem on a turbo car, where it also leaks boost-side pressure and heat onto everything nearby. Cometic's C4151-030 is a 3-layer MLS exhaust gasket for the B-series head that seals a slightly warped header flange and stays sealed through heat cycles that kill the stock gasket.

What It Is and Why It Works

Header flanges and heads expand at different rates, and on a car that gets driven hard the factory single-layer gasket eventually stops keeping up. Cometic's exhaust gasket is the same 3-layer MLS construction as their head gaskets: stainless layers with a Viton coating that seals against a flange that isn't perfectly flat and springs back after every heat cycle instead of crushing flat and going soft. It holds torque, so the flange bolts don't work loose, and it won't burn through or push out between ports the way a composite can on a turbo car.

It fits the factory manifold and every aftermarket B-series header with the stock 4-2-1 or 4-1 flange pattern. If you're installing a new header, use a new gasket; the old one is crushed and won't seal again.

Specs

Fitment

All B-series heads share the exhaust flange pattern.

What to Know Before You Buy

Clean the head face and the header flange to bare metal. MLS tolerates a little warp but not a chunk of old gasket. Check a used header flange for flatness; a badly warped flange should be surfaced, not shimmed with a thicker gasket.

Torque the flange nuts to spec in a cross pattern and recheck after the first heat cycle. Use new copper nuts on a header.