Landracing Forum
Tech Information => Technical Discussion => Topic started by: SPARKY on August 27, 2012, 05:27:01 AM
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Bobs comment "Comp Cams drilled the holes wrong"
Bob what I think you will find is that one of the down sides of running a really high lift cam in BBC and BBF your eng builder has to be really on top of his game. On both of them, you should install brass lifter bore inserts. The tricky part is one has to be installed high to keep the oil hole from being blocked by the high lift and the other has to be lowered to keep it from being bocked by the lifter being dropped by the smaller base circle required to get the higher lift.
Going to cams with the larger dia roller bearings help in this area.
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Thank's Sparky, It turned out to be a pretty simple fix, we ground a relief into both sides of the lifters from the lifter oil holes down to match the oil galley hole.
We had bought and used identical lifters before we installed our Jesel rocker system and had never had a problem other than wishing we had given a little more clearance allowance in the bores.
When we honed the Dart (Big M) block, I called both Dart and Comp Cams and neither would commit to giving us any guidance (the old "its up to the engine builder song and dance", but neither he or I had any experience with a motor meant to do what we are asking this one to do.
What essentially happened is that through lack of oil through the lifters, the push rods did not receive enough oil and it ate the top off of several exhaust pushrods and damaged two Jesel Rockers.
I had allready pitched the earlier lifters which were galled so I can't tell you what was different about the oil location, but it was another expensive lesson for a novice.
Bob
p.s., I just read your P.M. and thanks for the generous offer, but I think its handled. Bob