Groove In BBC Lifter Bore

[Dwight Southerland]

Originally Posted by carl hinkson

On flat tappet cams the lifter bores could be off .010 plus and not effect seat timing events as the cam is riding on a flat surface so to speak. If the lifter bore was off say .012 and you moved it in the opposite direction .024 which would be .012 off center on the opposite direction its not going the seat timing events at all.

That being said on roller lifters being off .012 plus it does change seat timing events which causes an intake and exhaust imbalance plus compression from cylinder to cylinder would not be the same.

Carl -
Not wanting to start a p***ing match here, but that is not exactly true. First, it is not a flat surface, and it does effect valve timing events. Secondly, I did not refer to valve timing events, but rather to valve train problems that are caused by harmonics. Thirdly, I agree with you 100% about lifter bore clearances and oil bleed off. Grooves are not necessary if everything else is kosher.