I just picked up this 96 z28 from a guy that told me it didn't start and just had a grinding noise. I immediately thought starter or flex plate. I got it home put a battery in it and it started right up only to hear this. Any help would be awesome. It doesn't sound like it's knocking but I've heard some similar sounds on youtube videos and people say it had a bad bearing. Any help would be nice to know what I'm looking at here rebuild wise.

 

Very well could be a bearing.

 

idler pulley, alt bearing, a/c comp bearing, P/s pulley bearing, water pump bearing....Good oil pressure?

 

the oil pressure sits pretty low at idle and then when I went to rev it it went up a little but the sound changes from a squealing to some rattle... I'm thinking it is a bad bearing
sigh

 

It kinda sounds like maybe loose torque converter bolts if its an auto... or maybe a throw out bearing if its an M6. Just trying to hit every possibility....

 

Did you run it with the belt off? Cracked flexplates sound a lot like that too.

 

it is automatic. and I just bought it off craigslist so I don't know what was done to the car beforehand.

 

it is towards the back of the motor for sure

 

I'd start with popping the intake and checking your lifters.

 

I would pull the trans shield and slowly turn the engine over and check for cracks and loose converter bolts before pulling the engine. Maybe you got lucky.

 

Pulled that cover off earlier and it looked fine. The squealing turned to knocking so I'm just gonna get it pulled out and torn down to see how bad it is.

 

any recommendations on a decent priced good quality rebuild kit?

 

Sounds like a bearing to me.

 

Find out if/how badly damaged your rotating assy. is before buying anything. Your best bet if you want to stay with stock displacement is the stock rods and crank.

 

Getting with a pretty respectable machine shop in my area and he's going to quote me the whole bottom end refreshment. Last guy he did an lt1 bottom end refresher said it cost him 400. So that isn't too bad. Next I'm onto the wiring harness. I'm trying to find out exactly what the bare minimum is to run the motor. I want to get rid of as much of the wiring and weight I can.

 

I'm thinking it is a bad bearing

 

are there any metal flakes in the oil???

if so...bearings....if not I would look closer at flexplate/TC and accessories before pulling and tearing down motor

 

Hard to tell what rpm the engine is idling in your video, but if near 800-1000, then it sounds like valvetrain frequency (1/2 crank speed) to me. And not at the top of the valvetrain either; definitely deep.
Just recently I had a roller lifter spall and flatspot on a high mileage L31 motor, and it had that same chirp/squeak sound, but I tore into it before it got as loud as yours.

 

Sounds like a bad alternator to me but my .2 cents me nothin haha. First do an oil change(check for metal in oil), try running the car with no accessory belt, next unbolt the inspection cover for the converter/flexplate and check to see if its broken and or loose bolts. Oil change will run you 25 bucks at most. Best to do the cheap stuff before a rebuild

 

I'm pretty sure it's a bearing guys I'll post and updated video of the sound now when I get home