Hi,i bought a set of upgraded lifters to Cosworth YB and got big problems. The lifters were still noisy after a few houres. After a few days i took the camshafts of and one lifter wouldnt out. And there was many deep scratches in 4 of the tappet holes(exhaust side). Oil pressure is 35-40psi at idle and 70psi at 4000-6000rpm warm engine(high pressure oil pump). What can cause this problem and is it possible to find oversized lifters to Cosworth yb engine.

 

scratches??
sounds like oil stavation to tappets, of debris in tappet iol gallerys
when you first fitted the tappets did they slide ok into their bores (snug fit) and not tootight or loose?
there are oversizes avalable but are rare.

 

I do not think it was enough clearance. Had to use Pliers to get out a lifter. It was only problems at the exhaust side.When I measured them, they were not round . Bought the lifters from Protech motorsport. The black lifters they sell. Better to buy INA lifters??

 

Deffo good to buy ina lifters, have NEVER had a problem with them yet since 2000 when i bought my car

 

If the tappets won't slide under their own weight into their respective holes don't fit them, there is absolutely no room for debris there, you won't realistically be able to tell to loose/tight as you should feel ZERO play, of course there is some but if it can be felt it's wrong.
AS the fault has occurred on just the exhaust side I would say the tappets are at fault.
If you use a 1000 grade wet and dry, with oil on it you can recover the bore most likely, but at worst a insert can be fitted, to recover it, you MUST really hard pack towelling around the base of where the tappet is first though if smoothing back.
Had this problem a few times, esp on cvh's, the last being on a "pro" built mega bucks xr2 race engine, had to actuallyforce one tappet out, then spent time lathing the tappet to get rid of bad marks, wet and dry on the bore.
tabetha