z24 rattling noise

[ari falco]

Hi Everybody , my name is Ari !!

I have a problem I can not find the solution to.
I have a nissan d21 hardbody 4x4 , 1990,with z24 engine (carbureted), new pistons, new cylinder head and gasket, valve lash OK!, The carburetor is ok!, No vacuum leaks,single spark , new timing chain and tensioner.
This is the problem:
I hear a rattling sound from the engine between gear changes or when I ease on the throttle, it sounds only when the accelerator pedal is in some kind of intermediate position, not in pull or engine braking mode , and Always after 2000 rpm.
(ignition seems to be ok, have not checked with a timing light)
If I screw the distributor to the end against the engine the rattling stops , but then, the engine has less power and low rpm on idle.
If I screw distributor to the end of opposite direction,(from the engine), increases the rattling noise but with a normal motor power at normal idle speed.
In any case, it sounds only when I have the accelerator in an intermediate position, not under load.
Has anyone encountered anything like this ?? , Or have any idea of what could be the problem ??
grateful for all the help I can get !!

[spitfirebill]

I would guess the timing chain guide wasn't set tight enough. At first I was thinking detonation, but that should happen under a load too.

[ari falco]

The problem with the engine and the noise is probably , (99.9 %) , that the cylinder head was milled down/resurfaced too many times.
I spoke with the former owner and was told that the cylinder head was resurfaced at least 3 times in his possession ,(and 2 times in my possession), it explains the problem.
I will of course buy another cylinder head, Used obviously because new is too expensive, but how will I know that this cylinder head does not have the same problem ?.
Is there a Resurfacing limit point where you can see if the head has reached its limits ??