ummm, thanks tabetha,
i have don around 4 k miles since rebuild, changing the oil and filter several time to cure this, including tappet changes. found no differance. iv measured tappet to bore clearances- all fine. iv had the head off to check the oil return valve ball bearing thingy, all seemed fine. im convinced now that their is a problem with the pump itself or pickup seal, or even pump seal to block. i no iv got a problem sumware. actual oil pressure wen running is in good.
my theory is if a pickup pipe is leaking then pressurised oil system will be airated hence playing my tappets up etc ??????? tabetha?