clacking noise

[rick1701]

g,day, i have a 1980 2 door rangie, fitted with a leyland p76 4.4v8 (which is the same as the leyland terrier engine) the motor was rebuilt by me 200 miles ago. and today as it got warm it started a loud clacking sound ,simalar to a lifter tap which seemed to disapear as i took it to 2000rpm. but as soon as i lift my foot off the pedal it comes back and is worse on idle. but if you shut it off for 20 min and restart it the clacking is gone, until she starts to warm again. when it,s cold the oil presure sits on 300kpa but as she gets hot the presure drops to 50kpa , but if i give it a hard rev the presure will go right up to 500kpa, it sits on around 250kpa doing 60mph in 5th gear. any idea,s ? please lol. the oil pump gears were one of the very few used parts i put in the engine, i,ve had rover engines make similar noises , and most times its a cracked piston skirt, or i,ve even had one 3.9 v8 separate a piston sleeve, but with those problems the tapping does,nt start until the engines hot, but does,nt go away no matter how hard you rev it, until it gets cold. could it be head related (valve guide)? anyway thanks in advance for your help.......rick