Asking as we had a 340 leaking from the heads last summer. Cometic MLS were used. We pulled the heads, put felpros on it and stopped leaking. My brother builds vintage Cosworth racing engines (70’s formula 1, F2 and the such) and only uses Cometics, he recommends putting a little RTV around the water ports on each layer of the gasket, along with copper coating the mating faces. If bolts are into wet ports, thread sealant is necessary when assemblying...
