Rings and bearings, a low km head with biger cams.I had to reshim to suit the big port cams;Im on the lines of keeping it under 3000rpm for 500km's with minium load where possibe; changing the oil and filter every 500km untill 2500.After every 500 km's my revs increase by 500-1000 rpm any thoughts ? i used ACL chr'molly rings ACL bearings (watch out though my 1st set of mains had a crack in them !!!!so i had to wait another week for them Thats y its taken 2 weeks to do the lot has cost aprox $350 i made up new gaskets where i could. Originally i done a h/g but i thought id do the bottom end to Lucky i did, it ended up chewing no2 bigend on the piston side; too much load /rpm and poss timing, no4 mains just started to go but clearence is still within specs