Bent Crank Shaft?
Discussion
In my yoof I was building a ff1600 engine next to an experienced engine builder who got the main bearings mixed up for a line bored block- his engine- and my standard block. He was delighted at how easily the crank turned and finished the build whilst I was off at college. Two days later I'm trying to figure out why my crank won't even sit in the block and he's got the back off the oil pump on the dyno wondering why there is no oil pressure. Ironically he was always telling me to check bearing clearance as it was critical to oil delivery especially at high RPM. To say he was embarrassed is an understatement! It taught me a bit about bearing 'nip' too!
Edited by Little Pete on Tuesday 25th October 10:37
When I was a teenager I built my first engine, on putting the crank thrust washers in I figured the grooves in them should face the block as it would do no good for them to be facing the rotating crank.
It lasted a few weeks before a strange knocking started and the crank began to slop backwards and forwards.
I think that was the same engine where (on picking the reground crank up from the engine reconditioners) I asked if they'd washed it, "Oh yeah, they said". Was knocking its tits off in a few hrs.....
It's certainly never happened again; you learn.....
It lasted a few weeks before a strange knocking started and the crank began to slop backwards and forwards.
I think that was the same engine where (on picking the reground crank up from the engine reconditioners) I asked if they'd washed it, "Oh yeah, they said". Was knocking its tits off in a few hrs.....
It's certainly never happened again; you learn.....
Put crank back after checking everything, and it now turns nicely by hand with a rag on the crank timing wheel, with the pistons in place, before I had to put a spanner on the crank to turn it even before I fitted the pistons, Only difference is that first time I used new old stock bearings bought locally, were as now I have new bearings from Paul Matty. The old bearings all look fine.
So not really sure what the issue was but all OK now.
So not really sure what the issue was but all OK now.
Berw said:
Put crank back after checking everything, and it now turns nicely by hand with a rag on the crank timing wheel, with the pistons in place, before I had to put a spanner on the crank to turn it even before I fitted the pistons, Only difference is that first time I used new old stock bearings bought locally, were as now I have new bearings from Paul Matty. The old bearings all look fine.
So not really sure what the issue was but all OK now.
Maybe on the original install a bearing shell wasn't seated properly. Glad it rotates freely now.So not really sure what the issue was but all OK now.
With old new bearings that have been knocking about for a while it only takes the tiniest scratch or burr or spec of dirt to eliminate the journal clearance. When you're talking about as little as 1 thou design clearance and when the average human hair is 4 thou thick you get an idea of how perfect the surfaces need to be.
It's extremely likely that if you examine the old bearings carefully there'll be a scuff on the back of a shell or a shiny mark on the babbit surface where a high spot was crushed down.
It's extremely likely that if you examine the old bearings carefully there'll be a scuff on the back of a shell or a shiny mark on the babbit surface where a high spot was crushed down.
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