Thanks again for your replies. Well I replaced the head gasket (350 Chev) and got it running OK, but only on 7 pots. My original problem was water in the oil. Off with the head again, send it to RocketDyne (local head specialist) for a pressure test. A bit of poking revealed a hole in the exhaust chamber - there's the problem. My engine had 2 different heads - the one with the hole was a 333882 (crap apparently) - the other is a 462624. Found 2 spare 462624's. The first one was cracked, still waiting on results of a recon on the other. I believe these are a better head anyway, although the valves are smaller than the 882.

Looking for a spare rocker cover so I can do my tappets hot as suggested.

Cheers
Graham