SBC rod knock with good oil pressure?

64FJ40 · Jul 5, 2007

I finally got my new-to-me 350 started the other day. The oil pressure is great (maxes out the stock guage - haven't hooked up the aftermarket one yet), but it has a knocking sound from somewhere in the bottom end. It almost sounds like something is in the pan and getting knocked around?

I'm going to pull the pan when I get a minute to hopefully see what's actually going on, but is it possible to have a rod knock and still have oil pressure at 70psi (guestimate) at high idle?

Boonie Buster · Jul 5, 2007

spin a rod or main bearing???

skrause · Jul 5, 2007

64FJ40 said:
It almost sounds like something is in the pan and getting knocked around?

Gee, that sounds rather reminiscent of the noises my 22RE was making. :redneck: :corn:

Binder · Jul 5, 2007

Possible but not real likely. There are many other reasons to have a knock.......

Boonie Buster · Jul 5, 2007

Binder said:
Possible but not real likely. There are many other reasons to have a knock.......

depends on how loud of a knock, cus i have NEEEEEVER heard a rod knock:haha: not with a chevy 2.8l... nOOOOOOOOO!:haha:

blackcj71 · Jul 5, 2007

anythings possible, pull the pan and move each rod and see if theres play. If the motors "new" to you the previous owner could have run it outta oil and fawked it up. drain the oil and see if hteres any metal in there. That might give ya a clue:awesomework:

crash2 · Jul 5, 2007

It could be piston slap/wrist pin or a problem with the rod bearing. Your first step is to kill cylinders while its running to see if you can kill the noise..

64FJ40 · Jul 5, 2007

blackcj7 said:
anythings possible, pull the pan and move each rod and see if theres play. If the motors "new" to you the previous owner could have run it outta oil and fawked it up. drain the oil and see if hteres any metal in there. That might give ya a clue:awesomework:

It came out of my brother's running & driving white trash Monte Carlo. It sat for a few months between when it last ran and when I got it in the truck, but it didn't have any problems when it was parked. The oil was fine when I changed it. It's definitely not a quiet motor (high compression, gear drive, etc), but this is certainly not right.

Thanks for the suggestions everybody. Hadn't thought of killing the cylinders... I'll let you know what I find out. We're moving this weekend, so I doubt I'll get to it until next week.

sandysfull-sizecarnage · Jul 5, 2007

does it knock ALL the time or is it when its under a load?

Binder · Jul 5, 2007

Something like that it could just have a dent in the oil pan.

pokey · Jul 5, 2007

you said "high compression" does it have forged pistons? They will rattle in the bores until they warm up and swell a bit.

64FJ40 · Jul 6, 2007

sandysfull-sizecarnage said:
does it knock ALL the time or is it when its under a load?

It hasn't been 'under load' yet. This is just starting and idling in the driveway.

Binder said:
Something like that it could just have a dent in the oil pan.

You know, I'm going to crawl under there in the morning and check that out. The more I think about it, that would describe the sound really well. I don't think I dented it putting it in, but there's certainly a decent chance.

pokey said:
you said "high compression" does it have forged pistons? They will rattle in the bores until they warm up and swell a bit.

I honestly don't know. I do know that the block was decked quite a bit, but I'm not sure about the pistons. The sound frequency seems to correspond to 1/rev rather than 8 though.