1200 miles into rebuild and got a nasty knocking from block at 2500 rpm, fuel pump died in tesco car park, fit new pump in car park, drove 5 miles home and knocking like hell.

new acl race bearings only 1200 miles gone, no oil light etc on tho, and idle well, only when i hold revs up a bit.

any ideas?

 

I'm sure others will be along with the usual questions in a minute...

- who did the rebuild?
- was the crank reground (if so, the left over metal particles will have probably wrecked the bearings)
- did you replace the modine? Assuming you had bearing failure the 1st time, there will be particles in the modine which may now have wrecked the new bearings

Other than that it probably depends on what else you replaced, running-in procedure etc.

 

i built it, only forged it, didnt have failure 1st time, rings chewed in bore. crank not re ground. didnt replace modine as no need.

 

OK - that's exhausted my list of stock replies then. Hope you find out what it was - and apologies for appearing (upon re-reading it myself) unsympathetic: not what I intended )

 

its ok mate, im just shocked it give out soo soon. il put a oil pressure tester on it to rule that out before i strip it.

 

Perhaps it was running lean with a weak fuel pump before it failed, creating det and ultimately bearing failure. Sickening!

 

By the above, do you mean that for the last build there was no modine refitted at all... OR... that you replaced the old pre-used one?!!!

 

check the oil pressure with a gauge, idealy above 20 psi at idle when hot, might have left something loose, eg. flywheel?

 

Oil pressure can still read normal even though it’s knocking. Cause can a whole host of reasons, Swarf, Clearances, rod Bolt Tq incorrect etc etc, pulling the block apart should show you what’s happened here, catch it while its early and you shouldn’t see to much expense.

 

Check the oil pressure first to see what you have.
Then bring the revs up to approx 2500rpm and as you release the throttle,if the big ends have failed you will hear them as the throttle is released.
As above in Un-Ink's post - the only way to narrow down the cause of failure is to strip it down, start with the oil pump to see if the PRV has jammed open in the relief position.



Mick

 

hi mick, its a rcm pump, with modified prv

 

Even with a modified 'straight bodied' PRV, they can and do jam open if there is the slightest bit of debris left in the oil system.
You can remove the PRV 'in situ' with a ball ended 10mm allen key as a quick check but unfortunately it sounds like the damage has already been done


Mick

 

well engines out, not fully stripped yet, head left to remove and oil n water pump.

the sump was full of copper shards, cudnt see much, con rods looked together, tomorro after work il remove heads and split block.

soon find out the extent of damage and if its damaged bores etc