engine noise?

[sdycke]

Hello. Just got a 91 with 13,000 miles but am not familiar with the LT5 at all. It has a slight engine noise that I wonder if I should be worried about . I know discussing noises in a forum is very difficult but who knows?. Its most noticeable cold and when you slightly crack the throttle. Then it pretty much goes away. It is a very faint, hollow knocking sound. Almost like a loose rod. I cant pinoint it whether its on one side or the other, but does sound more inside the engine. I may try shorting out plugs to see if that affects it. I understand these engines have some chain noise. I will be comparing it to a known good engine at the start of next week so that?s a start. I know these motors are bulletproof and the milage is low but I am finding many little things the previous owner ?forgot to mention?. Any seat-of-the-pants thoughts/diagnosis/opinions would be very welcome. Stan

[ittlfly]

If you are ruling out chain rattle on start up, then it sounds much like ''piston slap''....especially if it goes away on warm up. If so, it's nothing to be overly concerned about, just annoying. I had experienced it in my old 70 LT-1 after a rebuild.
I'm sure others will jump in here though with ideas.

[A26B]

Most likely piston slap if it goes away after warming up. Normal, no worries.

Very unlikely, but to test for rod knock; in 1st gear, at idle, apply brake and slowly release clutch until engine rpm decreases. if it's a rod, the knock will decrease in amplitude or go away completely under the load [not to mention, rod knock does not go away when the engine gets warm.]

[gbrtng]

It's an LT5 - they all sound like that. It will sound like that 200,000 miles from now.

[sdycke]

thanks for your great replies. will try the rod test for sure next time i head out. i'm just a little neurotic cause its only 3 months old and have nothing to go on. i read THOB and engine design/assembly was so crtical, not to mention the nickle balancing trick, I guess I was expecting perfection. piston slap was supposed to happen to the guy with the 01 malubu. and does.