2Fastbirds

iTrader: (1)

I've been reading through the old posts for quite some time and the search button has answered a lot of my questions, but I still have a few....

This is an 02 Z-28, auto. 62k miles on her.

I have the typical piston slap noise. I also hae the sewing maching noise. Most annoying when in line at a drive though next to a wall. I also have the injector tick that can be heard for blocks.

What I cannot figure out though is the rattle sound from the valvetrain when the car is coming back to idle from a rev. I have seen several videos in the posts but no one actually put their finger on what caused it.

This baffles me because the car is not down on performance at all. With lid and SLP loudmouth, the car runs 13.0 @ 108 n the stock Goodyears. It just sounds really weird.

Any ideas would be appreciated.

xirxious

Take the hammer away from the monkey, he will stop. j/k, mine makes a few odd noises as well, I've heard on other cars, loose pushrods will do it, the oil pressure on them locks them down and it goes away.
We had a list of smart alec replies from the airplane mechanics, stuff like the hammer,
'engine missing on take off' - after brief search, engine was found on wing.
'mouse seen in cockpit' - cat installed.
'plane lifts slightly with foreward pressure on stick' - stop flying upsidown.

BigBirdTA

So is it a rattle or is it a pinging sound (as I can imagine it would sound like if a monkey went at your engine with a hammer)?

Rattle = Something loose

Pinging = The motor might be detonating on decel (too lean when DFCO kicks in).

Describe it better or post a video or audio file. Also, more info on the car would help.

2Fastbirds

iTrader: (1)

Thanks for the replies!

There are a few videos here on the boards of the sound I am trying to identify. I will see if I can link to them.

The sound only occurs when the motor is decelerating. Does not matter if it is drive or in park. If the motor is revved and allowed to come back to idle. From 1500rpms down to 900 or so it sounds like ball bearing being tossed into a coffee can.

THe car is relatively stock. Has FTRA, Lid, SLP loudmouth and Predator tune. It has 62k miles on it and is a daily driver.

2Fastbirds

iTrader: (1)

Here is a link to the video.

http://lsx.streetfire.net/video/wm/3...5d0120ff28.htm

Sounds a little like piston slap but it does not go away when the motor warms up. Holding the idle at 1200-1400 also produces the sound.

BigBirdTA

Load some race gas or pull 4* of timing in the low RPM range. If it goes away it's pinging.

JedWele

Did you check pushrods to make sure you dont' have any slightly bent ones?

Thats one thing about the ls1 that sucks. They make so many ticks , taps and knocks you don't know whats normal and whats not sometimes.

Gh0st

iTrader: (3)

At first I couldn't hear what you are talking about but now I do, sort of sounds like a clanking type sound.

8a8mfh

iTrader: (3)

Heres my contribution http://www.jayscarsite.homestead.com/files/IMAG0023.AVI right click and "download as".
This was back at 29,000 or so miles and it sounds the same right now at 41,000 miles.
I got the car at 22,500, changed the oil a few months later, noticed the noise, GM replaced the lifters under warranty at 25,000 miles and a week later the noise was back.
It also ran unusually fast track times with a lid and LM 1 exhaust. Tried different oils and nothing helps. I've run the crap out of it at times and nothing has let go yet.
Also took all the rockers and pushrods out and nothing was wrong there.
I strongly disagree that it's detonation or pinging, theres no way it will ping under no load unless the timing is way way too far advanced.

BigBirdTA

That's why I suggested a simple test to eliminate pinging as the problem. I don't disagree, pinging usually comes on under load. But if he doesn't start a process of elimination of things of little or no cost, before he goes in deeper or starts throwing parts ($) at it, how is he going to troubleshoot the problem?

LS1curious

Excessive rod side clearance ?