Well have cured my mis-firing but car is now overheating and system is pressurising - you can see it from the radiator overflow even on tickover from cold. It does not get worse when engine is hot, so seems to indicate blown head gasket rather than cracked cylinder head. Not surprised after all the mis-firing that happened. :doh:

Have been reading RAVE but what is this about torquing up head bolts then running engine for 25 mins then doing again. Doesn't this means full assembly etc to run engine, then strip it again (drain rad, remove stuff etc) to re-torque? And do the head bolts really need to be replaced? never done this before on other cars, just re-torqued up the old ones.
All advice gratefully received. Thanks.

it should only be remove the rocker cover and re tighten you should be able to get to the head bolts quite easy

Whatever you do have the head pressure tested and inspected when it is off, I would also change the water pump and clean the cooling system. Only use genuine head gaskits, don't be tempted by cheaper copies. Also I have always changed the head bolts when I have done a head job in the past, its recommended and good practice. If you replaced the old ones and sheared one off you would just kick yourself. Hope all goes well.
Davie

Phew - thanks Chip

what about the head bolts, can I re-use the old one or are new definitely required? Anyone?