Scalpel

iTrader: (4)

His car is a bone stock 1998 Z28 MN6 that has an SLP air lid installed on it and 70K miles. It still has the stock clutch, etc but yesterday he left from a red light very slowly and heard a very loud knocking sound. We listened to it and it's an extremely loud metallic knock coming from what sounds like the rear of the motor. What could this be? He has an aftermarket warranty on his that covers it from bumper to bumper so his motor will be taken care of. We just wanted to know what it could be, spun bearing, etc and if it's something like this what's the best way to have it repaired, a new short block? Thanks.

AlonzoVersion 1.0

Sounds like rod knock best way to do it is get a new shortblock.

Scalpel

iTrader: (4)

TTT

MelloYellow

Alonzo said it.

You could either do a rebuild or wait for the rod to get throw thru the block. It shouldn't take much high rpm rev'ing before it dies.

Is the oil pressure falling yet?

Spun bearing.

Scalpel

iTrader: (4)

Oil pressure holds steady at 40 PSI at idle. (cold start)

Racehead

We can't begin to give you an idea of what is knocking since we can't hear it. Lot's of things can knock in an engine. Rod and Main bearings, a bad piston pin, a broken piston, some valve train failures can result in a knock. A broken flexplate can also have a knocking sound though it's usually accompanied by a rattling sound. Take it in and have it diagnosed and let us know what it was

Pro Stock John

iTrader: (34)

Put the stock airbox back on and get it fixed.

No telling what is going on in there.