Piston Slap

[nocok5]

Is piston slap common on TBI 350s? My 1990 Jimmy makes a knocking sound on startup only when it's cold. The oil pressure is good and there are no signs of anything hitting. I realize it could be other things, but I'm looking for suggestions on what to check.

 

[4xcrazy]

My 89 did that when it had its original engine at 225k miles. Did it until oil pressure was fully up and only for a couple of seconds at startup.
I'm suspecting this piston slap thing in the Avalanche though, some sort of knocking that doesn't sound like rods on the crank, but also not a lifter tick either and it only does it until it's mildly warmed up, lasting only for a few minutes.

 

[ryoken]

that rotating assembly architecture is not known for piston slap... plenty of piston above the wrist pin..

that said, a sloppy wrist pin can certainly cause it in most motors..

 

[Stomis]

I've never heard of it on TBI motors. Super common on factory LS's. Technically theres nothing terribly wrong with it as long as you let everything expand before punishing it.

Gm his behind the "its within factory tolerance" moniker when they're were called out on the noise. Same thing that causes oil use between changes. Its not bad per say just not tight tolerance. Obviously it can also stem from high mileage.

 

[blazer74]

There are certain years that gm knows about and at one time gm was extending the engine warranty to like 100K for engine knock/tick noise to satisfy customers.

That was quite some years ago but I know this because a buddy of mine had one.
90 something burb I think.

 

[Bowtie85]

My 97 k1500 has some slight slap when cold.....has 180 miles on it.

Also my old mans 77 C20 454 has some good piston slap when cold. Disappears once its warm. It's done it since day one, not a big deal in our books.

I'd just run it IMO.

 

[63chevyll]

Yeah pretty stand on GM stuff. Run it