ZZ4 68 Nova

My ZZ4 (gm 350) crate motor has had an irregular sounding knocking noise at idle lately and i cannot figure out what is causing it. I have changed my plugs, plug wires, and even fiddled around with the distributor and timing but the knock is still there, i also changed the lifters in the car just before i changed the other listed parts, but i changed those because i also had a noisy lifter as well as the knocking noise (just going over all the work ive done recently in case it helps).

The noise only occurs at low rpm and has no pattern, knocking at random times, sometimes its frequent and fast paced and other times it stays quiet for a few seconds. Once i rev the car up to about 1000 - 1200 rpm their is no more knocking and the engine runs perfectly.

Video of it idling at running temp (approx 800rpm): https://www.youtube.com/watch?v=29Wy...ature=youtu.be
Knock is much easier heard at high volume

Any suggestions or help is appreciated, as the "unsolvable" issue is driving me and my dad nuts haha. Thanks.

CamaroAJ

Whats the oil pressure at idle? And at 1200?

ZZ4 68 Nova

just went out and checked, @ idle the lowest it would go was 32psi, and @ 1200rpm it was up to 48psi. Running 20-50 non synthetic oil.

I uploaded a youtube video of the car idling, link is in the original post.

ZZ4 68 Nova

Still no solution, any ideas are welcome.

MVR 155

It almost sounds like something is loose somewhere? That's a very irregular kind of "knocking" noise. Check your bell housing bolts, actually had that happen to me once and it made a similar noise. May want to try using a stethoscope to see if you can isolate where the noise is actually coming from.

JimmyS5600

If it is a auto trans,check your torque converter bolts. They make a racket if loose

Lloyd Smale

almost sounds like a lifter isnt getting pumped up