knocking sound?
 

whenever my truck is cold and i just start it and let it warm up, i have to keep my foot on the gas for a minute to make sure it doesnt die. well whenever i blip the gas softly when its cold like that(never going above 1500 rpm's) the engine makes a loud knocking sound that i do not know what it is.

hopefully its a rod trying to push its way through the side of the block:cool:


it wants to be replaced by new faster engine

You might be getting your wish (hoping rod trying to push it's way through side of block), but because it goes away as it warms up I would go with your headers leaking a bit. As the metal heats, it expands and after a short while the leak seals and the knock goes away. I beleive a rod would knock more as the oil warms up and gets thinner.

headers should not be leaking. and the sound is coming from the bottom of the engine, and i know its not the collectors because i replaced the gaskets about 2 weeks ago.

i do not know if it has anything to do with my cracked flexplate though.

ocbaud, I've got the same thing going on w/my 74's 350. Sounds like a diesel when I first start-up on cold am's but after warm-up it goes away (or @ least it's undetectable). It's odd that it goes away so I'm debating whether or not to tear into it.

the reason it goes away when it warms up is because metal expands as it gets hotter. you possibly have a piston slapping against the side of the cylinder walls(i think that is the problem on the new chevys) but as it warms up clearances get tighter and there is no room for it to wobble around. possibly worn rings? just my thoughts...

THIS SEEMS TO BE A PROBLEM WITH ALL OLD HIGH MILAGE ENGINES. WHEN I HAD MY 305 IT WOULD ALWAYS DO THAT IT WAS REALY ANNOYING. IT'S JUST SOMETHING YOUR GUNNA HAVE TO DEAL WITH TILL YOU GET SOME MONEY FOR A NEW ENGINE.

I thought it was prob the rings but when I did a compression test it had between 155-165 psi on all 8cyl. so that's what what was weird. I would think one cyl @ least would have lower psi than the others or all of them would be lower psi than a 160psi average (from what I've heard, 160 is pretty good).

My 305 does the same, but it might just be my muffler w/ a hole in it. It wants to be replaced with a flowmaster! (I just want sound ok) Whenever I get the money... and remember what to spend it on... WHAT IS IT WITH PEOPLE AND CAPS???

Eric, you have a known cracked flexplate, correct? if so, that is probably your knocking sound. replace it, and it should go away.

scoti, was the engine hot or cold when you did the compression test? if it was warm then the metal was expanded, thus solving the problem. try it cold

hope you get it fixed soon. :)

hopefully soon