Thread: knocking noise

Tweet

Yes I am an engine hypochondriac (there I said it). I am constantly "hearing" noises, but last time it was true, so now I am paranoid.

I have a knock in my SBC (now that I finally got it mostly running right). It is possible that it is timing, but not certain (yes I am working on finalizing the timing, but waiting for the piston stop to arrive). Qjet carb with HEI and adjustable vac advance hooked to manifold vac. Flowmaster super 40 (loudish) with agressive, noisy tires (and I still hear it).

It knocks NOT at idle at all. I hear it mostly at 2000rpm cruising, much more when the engine oil is not fully hot (oil pressure is still above 30PSI). It does not get worse or less at higher rpm's or under load. When engine is fully hot, I barely hear it. I'm running 93 octane fuel and have 9.5:1 compression.

Plugs are reading nice and clean. I can think of the following possibilities:

1) timing too far advanced causing spark knock - My timing marks are now off, I plan on 12 static, 12 vacuum, and 21centrifugal with medium springs. I mostly have that now except I'm not sure about the static for sure and have not adjusted the vacuum canister yet. I did reduce the timing by 5-6 degrees with no noticeable change at all in this noise

2) Unadjusted rocker arm (loose). I am thinking this is more of a tick, and I would hear it at other times. When I am at idle or cruising at 1500rpm, things sound PERFECT.

3) Rod knock. Bad, don't think this is it.

4) I'm crazy, it's a noisy SBC in a big Jeep, get over it and drive it until something seems really wrong.

All gauges read good (oil press, temp, water). No hot engine issues. Oil pressure when hot is a bit less than 10 per 1000rpm. Oil pressure is about 5-8 at idle.

Thoughts?