Innosentz

As discussed in a previous topic 6 months ago I have a 73 cutlass S with the original 350 in it. It had a loud knock at idle that would go away when reving it a little. But would knock and "rattle" when you let of the gas.

I have pulled it for a rebuild. At first visual inspection the bottom end was fine. When I spun the engine over after a could rotations a main cap bolt fell out(right by the dipstick), second cap from the back.the threads seem fine and the bolt threads back in. I found a small metal peice in the crank case. The number 7 piston appears to be cracked.

I will I'll update this more as I continue the tear down. Has anybody heard of a cap bolt just loosening up? As far as I know and can tell this engine has never been rebuilt or even pulled out of the car. It has 61k original miles and my friend owned it for 30k of those 7 years ago.

Innosentz

Sorry I tried to post this in small blocks. Idk what happened. If someone could move it there I'd like that.

Innosentz

The number 8 piston is cracked. My apologies.

edzolz

HOUSTON, I think we have a problem!!

olds 307 and 403

Bearing looks good, maybe just a defective cast piston that broke away.

Sugar Bear

The rod bearing has a matte look to it as if it is quite new. Is there an oversize stamped in the back of the insert? Were the head gaskets steel shim? Cam gear nylon?

I have not seen main bolts come loose like that. Were the other mains torqued properly?

Definitely interesting...

Innosentz

I will need to go home later and check out the head gaskets. All the bearings and the journals seems to be fine. all of the cap bolts were torqued to spec besides the one on the same cap as the bolt that fell out. I was able to spin it by hand. I didnt see any oversize markings anywhere. The pistons are not oversize. Am i looking for an oversize stamp on the bearing? I was under the impression bearings would be undersized?

At this point i have it down to the bear block. All cylinder walls are fine and all journals are fine. Only the #8 piston was damaged all others were fine. No rods are bent.