Bought a 87 GTA a couple of weeks ago knowing the eng was knocking. (bought it mainly for the new 700r4 and 9-bolt rear)
Tonight I pulled the 350 tpi and tore it down.
Found all the pistons (except 1) have a chunk of their skirts broken off.
The chunks are abt the size of a quarter and make up the skirt extension area (no sure what that's really called. It's the lowest part of the piston that almost touches the crankshaft counter weight).

What causes this?
over-reving, sloppy rebuild, really worn out,???
Mileage is "unknown".

I don't have any history on the eng. other than at least 2 teenagers owned it before me.

The #1 rod bearing had spun which explains the knock. I'm assuming the bearing spun after the bits of skirt material made their way thru the eng. The crank is history.

Looks like I'm a good canidate for a 383 huh?

 

Could be any of the 3......or just cheep pistons.

 

Detonation

 

Detonation huh?
Hum, I did find the knock sensor unplugged.
Cyl heads were carboned-up pretty good also.
Bet you're right.

 

Broekn skirts = over-revving, which also explains the spun rod bearing.

Don't re-use that set of rods. The metal is probably already fatigued.

 

Yeah, if the case is still good, that complete 383 rotating assembly kit is pro'lly looking pretty good. If not, you still have the trans and diff.

 

Now I need a good deal on a 383 kit.
Any suggestions?
I want to use the TPI; so a cheap, low RPM kit would be fine.

 

When I rebuilt my engine all of the piston skirts were cracked. The machine shop said "thats what happens with aluminum pistons" I was short on cash at the time of the rebuild and I could not afford forged pistons. Now I am worried that when the engine gets up in mileage it is going to happen again.

 

I took apart a 307 out of a '78 camaro (still trying to figure out how it got in there the VIN said it was a 350- I was going to rebuild it and put it in my at the time 305 camaro) and all the piston skirts were broke and there were marks where they hit the crank counterweights, my dad said said the engine was overreved and, the rods were compressed to the point where it was possable to see the differnce between them and new ones.

 

The rod caps were a little tough to remove. I suspect the rods are a little tweaked. They'll be going in the trash soon anyways.