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Cold start piston slap on tbi

T

tbijimmy

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Lately I have been experiencing what seems to be cold start piston slap, I have heard about this with some of the work trucks where I work but they are newer vortecs, and mine is a fairly young tbi. it goes away after its warm and throws no check engine light. I was told on the newer vortecs (99 and up) that it is due to carbon build up on the pistons, but is normal and isnt harmful. my engine also doesnt seem to be doing as well at wot but i think it might be due to plugs and cap, but havent had a chance to look into them.

Can anyone give me an idea of whats going on, how to stop it, and if its damaging?

Thanks
 
Piston slap is usually due to excessive clearance between the piston skirt and bore. Forged pistons tend to slap a bit, with cast and hypuretic a bit better.
 
ktmoutfront said:
WOT should be avoided.
Click to expand...

Unless you tow with a V2500 burb with a 350. The throttle in that thing is like an on-off switch if you want to go anywhere.

That thing spends lots of time at WOT. Drive it like you stole it, right?
 
dhcomp said:
Unless you tow with a V2500 burb with a 350. The throttle in that thing is like an on-off switch if you want to go anywhere.

That thing spends lots of time at WOT. Drive it like you stole it, right?
Click to expand...

Well lets put it this way, I have fun with my toys :p:

I found there was a crack in my exhaust and that explained a noise I was hearing but I started it up when it was about 65 too warm it up and I didnt notice the slap and then changed the oil and didnt notice it then. I guess ill wait till I start it when its bellow 50 again.
 
My brothers truck is doing the same thing... He's gonna use some stuff that cleans out the carbon...

There was a similar issue involving carbon and clearance making a tapping noise on some Sidekicks... A buddy of mine found a forum where the guys having this problem used a product to blow out all the carbon and it fixed the noise issue...

I'm getting the name of the stuff from my buddy and we're gonna use it in my brothers truck... I'll post his results after he does it...
 
dirtygoat said:
My brothers truck is doing the same thing... He's gonna use some stuff that cleans out the carbon...

There was a similar issue involving carbon and clearance making a tapping noise on some Sidekicks... A buddy of mine found a forum where the guys having this problem used a product to blow out all the carbon and it fixed the noise issue...

I'm getting the name of the stuff from my buddy and we're gonna use it in my brothers truck... I'll post his results after he does it...
Click to expand...


seafoam?
 
ktmoutfront said:
Might be why things are going bad. Unless it is a built full roller motor, WOT should be avoided.
Click to expand...

??? Why should WOT be avoided? Its never hurt my non roller TBI engine. I have had my foot thru the floorboards and sitting on top of the throttle body many many times.
Besides... with the stock heads. A TBI 350 will never make enough RPMs at WOT in high gear to ever do it much harm.:D
 
Use heavier weight oil, let it warm up before beating on it, and don't cry when it breaks :) 350 SBC's are easy to come by so keep an eye open.... or rebuild it with the proper clearances.
 
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