quote:Originally posted by Coolvet:
So what is the solution George? You show a photo of sleeved lifter bores. Please explain what you have done here, why you did it and what the benefit is?
Thanks, I love learning how experts have solved these issues.
If i may be so bold as to answer on George's behalf, George please add to this or clarify it as you see fit.
The idea is :
the passage you can see in the lifter bore in the first pic, is in a 351c, the main oil gallery feeding oil to firstly the lifters but then the crankshaft main bearings and from there the connecting rod bearings.
You can see it is quite a large hole. The lifters don't really require the hole to be that large, a small hole only 1/16 of a inch would suffice to lubricate the lifters and the top end, but because of manufacturing reasons that gallery intersects with the lifter bores in such a way it produces the massive port you can see in every lifter bore.
This exposes the reciprocating motion of the lifters to the flow of oil going to the bearings. This lifter motion is tremendously fast and of course reverses in direction. This causes a phenomenon Known as Cavitation.
Cavitation is a void, a cavity in the oil consisting of vacuum or vaporised oil. This is not good to have going to your bearings !
This mostly is noticed at high speed above 7000rpm and is probably the cause of all those cleveland spun bearing stories i'm sure you have heard. I'm in Sydney too and i've heard a million.
The solution shown in picture two is to sleeve the lifter bores with bronze bushes with only a 1/16" hole for lifter/ top end oil, that way the oil flow does not get exposed to the extreme acceleration forces and motion of the lifters and hence cavitation is eliminated so the bearings get a uncompromised oil flow.
That's the theory of it anyway.