lemans1

iTrader: (4)

Hello everyone, this is my first LS1 car. It is a 98 Z28 with 112k. It kind of fell into my lap ultra cheap, but came with this noise. I dont know weather to call it a loud tap or quiet knock. When cold, you cant hear it at idle, only when you bring the rpms up. When warm you can hear it at idle, but its quiet. It sounds like it is coming from the pass. side near the top, but apparently sound travels well with the all aluminum block because it is equally loud underneath the car. I did pull the valve cover from the pass. side and check all the rockers/push rods and all looked good. Anything else it could be other than a rod bearing? I am hoping someone with ls1 experience can give me some advice. I would hate to pull the engine for a problem that could be addressed while still in the car. It definitely does not sound like a rod knock in an old iron engine, its too high pitched. Anyway, here is a video, let me know what you think. I can try and use a better camera if you think it will help. Oh, and the oil pressure is solid at about 40psi.

video at: http://youtu.be/6TXnhNGonZc

99Bluz28

iTrader: (35)

Check and make sure you don't have an exhaust leak.

I Confederate I

It gets faster with the rpms. Leads me to think a few things. First, change oil and look for needle bearings from the rockers, you won't be able to tell if one fell out without removing the rockers and knowing what to look for. If one did fall out, it usually ends up in the oil. Second, check for a bent pushrod. Pretty easy to replace if that's the problem. Third, it COULD be a shot lifter. That's pretty hard to diagnose without ripping the heads off.

Also, the previous mentioning of an exhaust leak could be your problem. As you said, aluminum tends to carry noise well, so if you have a leaky exhaust gasket the valvetrain noise will just echo out. It seems to be a bit loud for that though.

I do also want to point out that if you determine it is not the rockers, and it points towards a lifter problem, do NOT drive the car. You already ruled out the pushrods, so rockers or lifters are the only thing that comes to mind. Anyway, if it is a lifter, and you drive the car, you run the risk of grinding the dead lifter into the cam. Then you need a cam replacement as well. Not trying to sound negative, but that sound is awfully close to the sound I once heard in my SS. Luckily for me, my lifter was only "lazy", not dead. Meaning my car would only make the sound occasionally.

lemans1

iTrader: (4)

So the best thing to do at this point would be to pull the heads I guess. I don't think it is an exhaust leak, it sounds too metallic for that. I will check all of the rockers closely first, if nothing there, I'll go on to the heads. Thanks for the advice and the tips about the rocker bearings. I guess its time to hope for the best but plan for the worst.

Drewmeyes88

iTrader: (2)

Is the noise louder from up top or under the car? I was convinced my engine was done for and I was about to get a loan for a new engine. Then I thought maybe it could be my flexplate since I could hear the noise better from underneath the car and I've broken them on other cars. So I checked it and found a big crack in it. And after I pulled it I found out another bolt was sheared off into the torque converter. Just a thought for you, I know I was sick to my stomach when I heard it

lemans1

iTrader: (4)

It is more well defined from underneath. I was attributing that to no drivetrain noise, injectors, air, and so on.

Bradlyj8Z28

iTrader: (4)

Get a stethoscope from autozone and poke it around to see if you can narrow down the location....

I Confederate I

Pm me with what you find. I've run into quite a few valvetrain problems over the years, and I might be able to tell you what you're looking at.

kunkelz28

iTrader: (2)

find the problem? i have a similar problem so i am waiting to hear...

camminls2

i work for gm, in nwi, and sounds like the cam or lifters, we change cams in 5.3 6.0 6.2 u wouldnt believe how weak those cams are