bigfoot2thefloor

i just bought a 2000 trans am and found that its knocking pretty bad. i asked a shop what it was nd they said they think its piston slap but when listening to the sound clips on the site it doesnt sound the same. its more of a knock then a slap the car only has 30000 miles on it and has been running syn since 5000 with high test its whole life... does anyone else have any guesses or know of a way to check to see if it is piston slap without tearing the engine apart?

ArcticZ28

iTrader: (14)

Does it go away when the engine gets warm? The reason we have piston slap is because of the material the pistons are made out of. On cold startup, the metal is contracted, allowing greater clearances between them and the wall thus causing a slapping sound. As the engine warms, the pistons expand and it goes away.

bigfoot2thefloor

no hear it all the time... i wish thats all it was

ArcticZ28

iTrader: (14)

So it's certainly a knock and not something that could be in the valvetrain? Could just be detonation due to the tune being off somehow (which is all I can think of at the moment considering you said it has always run premium).

bigfoot2thefloor

not exactly sure but i played with the tuning and i changed some things that wernt to good but to my knowlege the timing is still stock...

bigfoot2thefloor

ok started it up today and its worse.. think its the valvetrain any ideas what to look for first?

bigfoot2thefloor

wait! i was just reading smokin t/a's thread and it said make sure you dont miss a shift... now when driving the car i noticed whenever i floored it at the end of each gear it bounced off the rev limiter...i pluged in the hypertech he gave me and found that he had the rev limiter was set at 5800 butit was shifting at 6000... so i changed it and it doesnt bounce it shifts nicely.. could that cause damage or was i just not getting full potential out of the motor?

linegtdt52

iTrader: (12)

If it does it in rotation, when its cold and be very careful, put your hand on top of vavle cover on what side its comming from. this is just to get and idea of where its comming from. get you a set of ears and listen to the short block then the top-end. its hard to say because vibration and noise travels. probably a burnt valve thats not seated right or a spring. make sure you dont have any exhaust leaks near headers it can be misleading

67Firebird455

iTrader: (27)

I agree, an exhaust leak sounds nasty. Check to see if the knock is coming from the pan area, or up top... If it's a ticking kind of knock, check for a bent pushrod or such. It's relatively easy to pull the valve covers for the sake of your wallet and that poor car. Worth a look.

bigfoot2thefloor

yea i tooka closer listen and i think i agree its coming from the 2nd piston on the drivers side.. im gunna open her up and see what i can find thanks for all the help..