Hi all,
Thanks in advance to anyone who can assist with the following;
I'm in the reassembly phase on a bottom end re-build of a 1970cc CF3 twin spark engine, which has been battling me from the start.
Latest problem is that there is evidence of interference between the side of main bearing #1 journal and the rear gerotor cover of the lube oil pump.
Clearly the two have been in previous contact with signs of spalling on the oil pump cover corresponding with the side face of the #1 main journal.
Crank is fine (just crack tested, re-ground 10/10 and polished), end float is in spec. Nothing untoward on the crank noted during inspection by myself and also the machine shop.
It's clear that the #1 journal clearly stands proud of the block by a couple of mm, (don't have exact measurements yet, but will survey in the next few days).
At some point they have clashed in the past as the inspection of the oil pump revealed yesterday.
So, either one (or a combination) of the following must apply for this to occur:
a) The #1 crank journal has been manufactured incorrectly and is too wide.
b) The block is machined incorrectly in terms of the thrust bearing register location e.g. to far towards the free end of the block.
c) The oil pump is incorrectly manufactured.
d) The oil pump is ok, but is for another variant with different stand-off spacing and therefore reduced clearance on the CF3.
e) Someone has replaced the oil pump previously omitting the gasket, then removed and refitted a gasket because there was definitely one there on strip down.
Just wondering if anyone has seen/heard of anything like this before?
Assuming the interference still exists (ref e) above and the fact that I haven't accurately measured yet), the current plan will be to machine ~.020" off the back of the gerotor cover to provide at least .020" clearance.
Thoughts & comments appreciated
Vne
There was a change of oil pump, and maybe a change in the block - which I now can't find any mention of. No mention of changes to the crank.
Did check briefly last night, but no obvious clue that I could see.
That would make sense though - possibly wrong part installed.
I'll check again.
Just for info, it has been suggested to me elsewhere that worn thrusts can cause this to happen - poster thought it was a noisy clutch throw-out bearing but found the noise persisted after it was replaced. New thrust washers solved the issue.
I didn't measure crank end float before strip down, but no significant wear was noted when the thrusts were removed. Design clearances must be right on the feathery edge for this to occur. Will measure and see what we've got. Might be good info for folks to know.
Sorry to hear of such a marginal situation. You'd think the changes in end thrust from varying geartrain loads would predicate a sensible clearance at the start.
Do you think there's any mix-and-match gone on with the oil pump?