I'm buying an 84 300zxt for $350 and all its 'sposed to need is an alternator... well... I fiddled with it a lil and got it started and theres a bad knocking, which personally to me, sounds like the lifter valve, valve lifter... whatver... well... I used an engine additive called CD2... its supposed to clean up noisy lifters, valves, and something else... so I put in 2 bottles when I changed the oil out and the damn things still knocking... now either the CD2 stuff I bought sucks ass, or it a rod knockin So the question is, how hard is it to replace a...rocker arm I think it would be... how much would it cost... or how much would I look at for another engine. If its a lifter, same questions.... how hard to replace and how much if I payed someone to do it... The engine is a VG30ET. Thanks.