lowtower

Hey Gents, Having trouble with a distributor knock after engine is running and warming up. Noise is not there when first starting. A little history, engine is a 1974 350 small block. Has 75,000 + miles on it and was running good until car was sitting for 3 years. Replaced starter, fuel pump, alternator, p/s pump, water pump, new hoses, new HEI dist. etc. Had a knock at distributor and timing chain cover when engine was warming up but not at cold start, only after engine temp was about 150-190 degrees did the knock start. Removed timing cover and found chain loose. Replaced gears and chain, replaced cover and started up. Noise is gone in cover but still there in distributor. Used stethoscope and hear it only in dist. Replaced dist to another new HEI. Replace rotor and cap twice on HEI just to rule that out. Checked cam gear and oil pump shaft, both look good. I have lumps on my head from banging it against the fender trying to figure out what it could be. Any ideas??

jfmorris

Good luck! Sure sounds like you replaces a lot, but unfortunately, the last time I owned and worked on a mid-70's 350 small block was in 1989, and my memory doesn't go back far enough to remember any sounds from the distributor...

I never owned a Nova, but did own a Pontiac Ventura and an Oldsmobile Omega - same vehicle as your Nova but just with a different grill and a few trim differences.

Worst thing that happened to me was that the 77 Ventura slipped the timing almost 180 degrees, 4th of July weekend of 1986, and had to be towed home. Replaced the timing chain and both gears, as the crankshaft gear had lost half the teeth into the oil pan! I had turned it off at just the right time for the chain to be in the position to slip. GM had used a cast iron gear with phenolic teeth bonded to the metal, in order to make the engine run quieter. I remember standing at the NAPA counter and being asked if I wanted the same gear or a 100% metal one. You can guess which way I went! I didn't care about a little chain noise, so went with the full metal crankshaft gear.

If you have pulled the distributor shaft and gear out and replaced them, that really only leaves the gear it meshes with down in the engine as a source of noise, in my mind. And that's a lot more to tackle...

lowtower

Thanks jfmorris. I know time is not fair for ether one of us. As it has been a while since I had to wrap my brain around engine noises. I'm going to have to keep asking until someone gives me an idea or I have a brain fart and an idea pops into my bald head!!!