Knock or Piston Slap ?

**kool-aide** · 11-17-2007, 06:06 PM

I was changing my water pump the other day and while the car ran i noticed it sounded like a baby desiel. I have read and heard about piston slap. I drove a 98 T/A that very much sounded like a full on desiel. I thought piston slap "went away" when the engine warmed up?

So i let mine idle until it reached temp plus a couple minutes. Didn't time so guess about 10 minutes or so. I'm going to try and record a little bit and see where i can post it. I have almost 97k miles. I have been working on tuning it up, plugs, wires, fuel filter, PCV, oil changes, trans mount, motor mounts, TB cleaning at the shop, water pump (not by choice), belts, hoses. I'm in the process of getting new O2s. I have only put about 7k in 11 months on it.

I'm not throwing any codes. It used to off and on, like a couple days on a few days off. that stopped, and I never got a scanner on it in time. I used to run , gulp, 87 in it. I have put two tanks of 93, and plan to stay that way.

Any thoughts? Is it excessive knock or just the way my LS1 is? From my seat of pants meter it runs strong and is fun as hell. I have never driven a f-body with a v8, so i have no idea if i have power loss. I was reading about nkock sensors cuz i don't know what they do. Since i have no codes i am assume the PCM and engine are happy buddies.

thanks

kool-aide

**Starion** · 11-17-2007, 10:33 PM

I've heard a little bit of piston slap in mine on a cold start. It doesn't sound anything like a diesel, though. Just a little ticking. No noise at all after it warms up.

**kool-aide** · 11-18-2007, 05:20 AM

ok i have video / audio. now i need to find a place to post it.

have no idea if this is the right link, but here it goes,

This is my first YouTube, so if it doesn't work let me know. I was trying to find a place to post my clip, and this was all i could think of in two seconds.

To me that subtle background gurgle (sp ?) slash odd rumble noise is what I call a baby desiel.

In the 98 T/A I drove it was like 10 times worse. This i smy 99 Z28. Don't know if this is typical LS1 or not. I read the owners manual and it says 91+ octane is recommended but you can run 89 or 87. The only thing is says you can't run is below 87. Any way I have 93 in now.

thanks

**kool-aide** · 11-19-2007, 10:48 AM

any? no takers on this curious noise? I think it is normal.

I was surfing you tube sunday and listening to various LS1s out there. I came across one that was cammed but under the hood i swear it made the same baby disiel rumble. I'm starting to think this is normal.

**Rhinohuey** · 11-19-2007, 11:02 AM

Just listening to the video, I didn't hear anything out of the ordinary.

**kool-aide** · 11-19-2007, 01:28 PM

that's reassuring. The only V8s i ever owned were a Mopar 318 and 360. You don't get curious noises with that block. This LS1 has been, well, different in a plessant surprise way. Thanks.

**Rhinohuey** · 11-19-2007, 02:15 PM

I've owned 2 other SBCs, both 1970s, and when I got my LS1 every little noise made me think something was wrong. I was just paranoid. After hearing other LS1s, LS6s, etc. you realize that they all make different sounds when they're running.

**kool-aide** · 11-19-2007, 02:27 PM

cool, yeah you do get paranoid because you spend money on a passion and don't want it to go down the toilet. I do all my own work, so I try to get to know it very well. It is a very fun hobby and definitely keeps me busy from time to time.

**jigger1166** · 11-20-2007, 02:08 PM

Originally Posted by kool-aide

ok i have video / audio. now i need to find a place to post it.

have no idea if this is the right link, but here it goes,

This is my first YouTube, so if it doesn't work let me know. I was trying to find a place to post my clip, and this was all i could think of in two seconds.

To me that subtle background gurgle (sp ?) slash odd rumble noise is what I call a baby desiel.

In the 98 T/A I drove it was like 10 times worse. This i smy 99 Z28. Don't know if this is typical LS1 or not. I read the owners manual and it says 91+ octane is recommended but you can run 89 or 87. The only thing is says you can't run is below 87. Any way I have 93 in now.

thanks

I watched the video, and the noise sounds just like my car. (piston slap)

**kool-aide** · 11-20-2007, 02:35 PM

yeah, iwatch about 2 dozen videos on you tube last night. They all had various levels of the same sounds. I watched Camaros, Firebirds, and Corvettes, all the same.

I feel better and reassured.

**Starion** · 11-20-2007, 07:23 PM

Yeah I don't hear anything out of the ordinary there. Might just be what people refer to as the "sewing machine" sound of the ls1. Just normal valvetrain noise.

**qwk93ta** · 11-21-2007, 08:17 AM

My 00 WS6 has piston slap on a cold start for about 2-3 minutes......

**kool-aide** · 11-21-2007, 10:43 AM

ah yes, sewing machine is probably better description than baby desiel, cuz it never really gets louder as you rev.

**Soltakr** · 11-21-2007, 02:17 PM

Mine does it too. Corvettes of the same years have that issue too. Here are some of my thoughts, all alumiun engine transmit more noise so you tend hear that stuff move. Plus the pistion rings aren't that great on LS1 and (worse on LS603-04) so it takes some time to harm up then expand and stop the slapping. Another is that GM know about this a did it anyway, a little built in obsolescence is good for busniess. There is no money in a perfect car.