Question : knock when cold but almost goes away when warm

[alenhoff]

any help would be appreciated, i have a 93 lumina z34 with the 3.4 in it. it has a knock at cold start but almost goes away when its warmed up. i've listened to it with the use of a hollow pipe and it sounds like its in the front head. i've pulled the cover off the carrier and the cams and lifters look fine and don't seem to be making the noise i'm hearing. when i listen further it seems as though the noise is coming from the cover on the drivers side of the head. i would have thought all that was under there was the ends of the cams but before i tear down further i would like to know your opinions. i did do a compression test with all cylinders hitting the specs just fine. just wondering if anyone else had the problem before. thanks in advance.

[pocket-rocket]

Without hearing it I would think piston slap.

[alenhoff]

well with the plug wire off it still knocks. with the plug out the knocking is gone. so a piston slap does seem right. i appreciate your help

[z34gtp383]

engine

did you make sure your coolant was full? if you were low on coolant? i mean really low, the engine will overheat and also cause the piston to collapse.are you getting alot of blue smoke out the back? did you do a compression test? that there should tell you. good luck. look at my pics before and after, new 3.4 dohc engine. look at the piston and the head.

[Schurkey]

http://60degreev6.com/forum/f100/camshaft-noise-gm-bulletin-t39793

Both my 3.4s rattle like death, especially cold. Could be piston slap, too.

[hok666]

so the service is no longer available? thats BS i just started noticing ....the same problem over the last two weeks....