Tappet Adjustment - bigger issue?

[zedevan]

My l26 recently developed a bad tapping noise, i've adjusted the tappets to .25 for inlet and .30mm for exhaust when at operating temp, i'm sure they are as close to spot on as i can physically get them!

At one stage the noise got worse as i hadn't tightened the locking nut up enough so it had moved quite a bit, and after fixing it back up and checking them all again, going for a drive and checking them again i have no idea why the noise is still happening.

Currently when i start the car (it doesn't blow heaps of smoke when started which i read was one way to see if the valves weren't sealing.) the noise isn't there and it all sounds normal, then as soon as its revved above approx 2000rpm the noise happens and stays there when the rev's are lowered back to idel for a bit over half a minute and then its silent again until revved. This made me think it was possibly an oil problem so i've cleaned out the cam oil distributer and ran it with the cover off and they all put out oil!

any ideas? is it bad to drive my car with this noise happening? well i realise it would be bad (i'm not overly attached to keeping this motor running), but is there much of a chance of it braking down on me by something major failing? as i really want to take it on a nice long drive tomorrow.

Thanks, and sorry for the long post - Evan

[d240zx2]

From your description, it sounds as if there is metal contacting metal. A cam lobe slapping the lash pad is possible. There could also be a valve stuck partially open, allowing the high part of the cam lobe to slap the pad.

There's a product here in the states that I've used for many years that may take care of the problem if there is a valve sticking issue....Marvel Mystery Oil. I know, the name sounds like a snake-oil concoction, but it really can work wonders. Just add a pint to the crankcase and let it idle for half an hour.

Further, have you tried isolating the sound using a stethoscope or stethoscope-type device? By listening through the valve cover, you may be able to discern which cylinder is creating the sound and diagnose from there.

Just a few suggestions...

Frank