hello mate.... will cause damage to valves but to be honest you can get a 2nd hand lump or head for peanuts..also dead easy to change a head on them especially if complete i done my rs turbo head on and off in about 1 1/2 hours if that,

new cambelt kit is about 20-30 quid
head gasket kit for about 20-30
2nd hand head anywhere from 99p on ebay

good luck fella

oh and recommend new oil, oil filter, plugs etc ....full service kit inc oil about 40 quid!!!

and gives you something to do on the weekend!!