1979transam

iTrader: (19)

Every since it got cold outside everytime i start my car it makes a weird knocking sound until it starts to warm up is that normal or do i need to have it checked, the car isent running different or the Check Engine light isent on or anything so im hoping its nothing to worry about

leave me some comments

stoverz28

iTrader: (8)

could that knocking sound just be excess valve clatter while warming up. If so its normal.

Gaunt

iTrader: (11)

piston slap?

LS1Silverado05

iTrader: (41)

Its highly unlikely anything is wrong. Most of these motors make some noise. But hey, horsepower makes noise.

1979transam

iTrader: (19)

no i dont think its piston slap its like a ticking noise if it was something bad it would be constant im going to have to agree with stover its prob just the motor warming up and its making a ticking noise

HOPEFULLY

Gaunt

iTrader: (11)

If you could take a video of it or something along those lines, that might help.

Cold starts = noise for the most part as well.

Also a good sign the SES light didn't go off.

PLucas

iTrader: (1)

sounds like piston slap to me

Z28LS1camaroguy

iTrader: (3)

if its a light tapping sound than its just valve chatter or piston slap, perfectly normal and it takes longer for that oil to get hot and running through the engine.

1979transam

iTrader: (19)

so nothing to worry about, perfectly NORMAL for it to do that when its cold??

Z28LS1camaroguy

iTrader: (3)

yup normal LS1 valvetrain for yah.

Asmodeus

Yes. It's piston slap. Don't worry about it.

stoverz28

iTrader: (8)

What exactly is piston slap caused by?

Asmodeus

short piston skirts, pistons that need to warm up to expand and completely fill the cylinder.. a combination of those 2 really

z28bryan02

Normal, my car sounds like a sewing machine sometimes

Z28LS1camaroguy

iTrader: (3)

yup everyones does, just gotta let them warm up.

ae13291

iTrader: (8)

my car is the 99 ls1 and i hav never experianced piston slap or any knocking when cold! when cold my oil pressure is close to 80 psi and i use 5w30 M1 so is it normal or is mine better or somethin

Gaunt

iTrader: (11)

Good! Also, how cold is your cold startup? Some peoples definitions of cold can change so take that into account.

Not all LS1s suffer from piston slap, but if yours does, don't worry about it basically.

Asmodeus

He's from LA.. cold start-up to him is probably 50 degrees

Cold start-up to me would be 10 degrees or lower.

JedWele

LS1's are very noisy engines. Even some diesels get jealous. ;-)