UL 40`s valve covers....

Hi there,the rebuild of my U engine,tranny has finished at last......its running great so far(150miles)but i cannot get the the valve covers to seal,all the parts are good used oem ,but the springs are new.....i tapped them down onto the cork washer with the front of a screw driver gently a couple of times but this did`nt help....is there any tricks???could they need more miles to sit right???any help would be great......Thanks....

Seller shows a parts breakdown?

http://cgi.ebay.com/ebaymotors/ws/eBayI ... _Stores_IT

YP you probably know but ... did you flatten the bottom cups(that hold the cork)so they sit flat on the gasket, when you assemble for the first time put the corks(inner tube cork also) in hot oil/water so they get flexible , or just change the corks for O-rings.
Mine is staying clean with the O-rings.
Stéph

I switched to o rings some years ago also. It stays pretty dry. If it's reallyl blowing oil, you might want to double check the breather timing. excess crancase pressure will force oil out all the cracks.
Dr. Dick