LT-1 Engine noise cold, Piston Slap?

[yadawho]

I recently had my 1996 LT1 in for a knock cold, the dealer explained this is a normal piston noise and not to worry, all knocks worry me with the cost of repairs these days. Anyone have thoughts, or maybe the same situation with their LT1? I should mention the noise is gone after a few miles of driving.

 

[jmccloud]

Cold engine noise

Have you changed the oil lately?

 

[Hib Halverson]

Whether or not the oil's been changed is irrlevant but what is somewhat related is the viscosity of the oil being used. Is it a 10W30?

Also, has this engine always had a knock when cold?

Typically cold piston knock will have these characteristics.

Only when cold. Goes away quickly after engine start. Has a medium pitch and sounds sort of like a lifter or a rocker arm. Is not very loud. Usually can only be heard with the windows down or from outside the car.

Gen 2 SB V8s are not known for cold piston knock.

 

[yadawho]

Oil

Oil is full synthenic 5w-30w,it has around 2500 miles on change

 

[jmccloud]

Oil

Smell the dipstick to check for fuel (gas) aroma. A leaky injector could dilute the oil and reduce its effective viscosity and 'clinging' which can produce start-up noises and faster engine wear.
Good luck.

 

[yadawho]

There are articles on the internet about both LS1 and LT1 piston noise, there is an actual sound recording of normal (quote from gm) knock, it is loud, and it is a hammering noise not a lifter tick, just by the way it changes with engine RPM indicates to me it is piston noise, and it can be heard window up or down, goes away within a few minutes. I am pretty certain of opinion on this noise, I myself am a master mechanic with 30 years in the dealers of domestic and import car lines. My warranty runs out in 5 months, that is why I wanted to hear from other owners on this noise before I become more aggressive about getting it repaired. Thanks for the help.

 

[Tuna]

The only knocking noise I ever heard from my LT1 ('92) turned out to be 'fuel line hammer'. Only happened with near freezing or below outside and only lasted a couple of minutes. Definitely was not piston slap and never noticed any sign of piston slap in my car. With CORSA exhaust installed, couldn't hear it if it tried now.