metallic knocking sound after start-up

[F-BRD_fan]

i have this problem during start-up of the bird. sometimes the engine makes this sound like metal hitting metal. metallic knocking sound basically. when i tap the gas the tempo of the metallic knocking sounds rises. then after a minute or so it stops and the engine runs as normal..hoping you all might and idea of what could be the problem...also just want to thank you guys for the knowledge and good advice that is put out on AF, best forum on the net.

[79Bandit]

Originally Posted by F-BRD_fan

i have this problem during start-up of the bird. sometimes the engine makes this sound like metal hitting metal. metallic knocking sound basically. when i tap the gas the tempo of the metallic knocking sounds rises. then after a minute or so it stops and the engine runs as normal..hoping you all might and idea of what could be the problem...also just want to thank you guys for the knowledge and good advice that is put out on AF, best forum on the net.

Sounds to me like piston slap...if it goes away after the engine is warmed up then thats probally it piston slap..dont worry then because its not doing any damage.

[F-BRD_fan]

hey Bandit is there someway to prevent "it" from happening?..

[79Bandit]

Originally Posted by F-BRD_fan

hey Bandit is there someway to prevent "it" from happening?..

for an easy fix...im not sure maybe mr.lous would know the only thing i could tell you is to break her apart get to the pistons and see if theres a gap there...but i would not do that untill a proffesional had told me that it was piston slap...

http://www.pistonslap.com/
http://www.allpar.com/fix/chatter.html

those pages might give you a heads up to what your going against.

[Mr. Luos]

Year of car?

[Rmbodie]

Google the term "piston slap" and you will get lots of info about it . LS1's are well known for it now . Alot of the new alluminum block engines do it . I only notice mine in the winter months . Rob

[RG501]

i have that too on my 96 FireBird. it almost sounds like its comming from the exhaust. im thinking its piston slap though.

[Mr. Luos]

Piston slap is an LS1 issue. Not an LT1 or V6 issue.

[Rmbodie]

Not argueing with you Lous but there are 8 different engines from 3.1 to 8.1 that have the piston slap according to www.pistonslap.com. My wifes 3800 gen 3 has it . Rob

[Mr. Luos]

They can have it.
It was mostly an issue with the aluminum blocked vehicles though. Heat expansion issue basicly. Aluminum changes more under heat than iron.

[2000LS1Z28]

Originally Posted by Mr. Luos

Piston slap is an LS1 issue. Not an LT1 or V6 issue.

You can have piston slap with any car.

GM goofed up and overbored the cylinder head walls, cause the pistons to slap.
I owned an LS1 with piston slap (My former 2000 Z28). It's very common amongst the 98-00 models, and less so with the 01-02's. In order to repair it they need to do a tear down of the engine. You're looking at well over $1K for repair. I was told that they'd take the block apart, acid drop it, put in new pistons (Non hypereutic pistons, cause they suck ass), and I thought he said sleeve the block. Not to sure though. I said screw it, and traded the car in.

If it is only the noise, i'd say screw it, as it isn't a real issue, after warming up. My former Z28 outright sounded like a diesel truck. I was told to use heavier synthetic oil 20W.

Hopefully it is just a bent pushrod.

[79Bandit]

ahh i didnt even think about that yea my trans am had that sound (something like piston slap sounds like) and when i tore down the block as yo ucan see from the pictures on my post labled *and it begins* there was a shattered rod and a bent one. that could very well be the problem if it just started happening