Mobil1 0w40: LS7 Corvette Z06: 2nd Report

[Dirty_Howie]

Well my 2nd motor now has 15K miles and 7 track days. This last sample was with a little more than 5K miles and 3 track days. I added 1/4 of a quart of oil in that time.

My motor continues to make the clackity-clack noise when cold at idle. Any increase of RPM and it goes away. When the engine is fully warmed up the noise is gone and it sounds like a normal LS7. I don't know what the noise is but apparently it is not causing any wear.

DH

 

[beast3300]

Superb report! Thanks for the post!

 

[addyguy]

The clackety-clack when cold will be pistong slap, a normal occurence in GM engines.

 

[Dirty_Howie]

Originally Posted By: addyguy
The clackety-clack when cold will be pistong slap, a normal occurence in GM engines.


I have heard everything from exhaust leak, piston slap, rod slap and stuck lifter. Supposedly, the LS7 does not have the piston slap that was common in the early LS1 engines.

Everyone seems to agree that if was something bad I would get worse when hot and higher rpm. And the UAO seems good and used only 1/4 qt in 5K miles and 6 hours on the track!!

DH

 

[SteveSRT8]

Note that these engines are also famous for "carbon knock", often mistaken for mechanical issues.

Normal piston slap goes away when the engine warms a few seconds, if it slaps all the time there can be an issue.

 

[Dirty_Howie]

Originally Posted By: SteveSRT8
Note that these engines are also famous for "carbon knock", often mistaken for mechanical issues.

Normal piston slap goes away when the engine warms a few seconds, if it slaps all the time there can be an issue.


Do you mean predetonation as from carbon buildup ?? This is a new engine (15K miles) and has been making the same noise for at least 13K miles.

DH

 

[SteveSRT8]

nope, I mean carbon builds up in the head and causes a knocking sound when the engine is idling that sounds like piston slap.

Noisy lifters/valve gear are going to be at half speed, knock from pistons/carbon, etc. will be at regular engine speed.

 

[Dirty_Howie]

Okay, thanks.

I will have to find the video I took with the sound and post the link up for you.

DH

 

[steve20]

Hey Howie
Just curious what the OLM was reading at 5K with 3 track days-any idea?
Also, do you remember max oil temp during the last 5K?
Steve

 

[Dirty_Howie]

Originally Posted By: steve20
Hey Howie
Just curious what the OLM was reading at 5K with 3 track days-any idea?
Also, do you remember max oil temp during the last 5K?
Steve


My oil temps on track are 260*
My oil temps on street driving range from 165-200* depending if I am cruising on the freeway or hot rodding around.
I think I still had 50% life left.

DH

 

[A_Harman]

The clackety-clack sound you mention in your first post makes me believe it is piston slap, but I have never heard of that occurring in LS7's. My LS1 has had it since new, and at 184k miles, I'm not very worried about it. After 10 years of driving, it still sounds the same. The sound is loudest when the engine is first started, and goes away if I rev it over 1500 rpm. When the engine is fully warmed up, it is faint. After a good 20-minute lapping session, the engine runs very silently. Hotter pistons close up the cylinder wall clearance and quiet the slap.

 

[Dirty_Howie]

I'm not saying its piston slap because I'm no mechanic. I would like to know what it is making the noise. I'm hoping its nothing serious and was looking for the oil analysis to show a problem or not .........

DH

 

[steve20]

Originally Posted By: Dirty_Howie
Originally Posted By: steve20
Hey Howie
Just curious what the OLM was reading at 5K with 3 track days-any idea?
Also, do you remember max oil temp during the last 5K?
Steve


My oil temps on track are 260*
My oil temps on street driving range from 165-200* depending if I am cruising on the freeway or hot rodding around.
I think I still had 50% life left.

DH



Thanks DH: must be the 10 qt sump giving such good results-my 02 LS6 OLM was done by 5K and I drove it like Grandpa(most of the time) mine ran hotter too---190-230 on the street

 

[Dirty_Howie]

For those that are interested or might be able to diagnose this noise, here are some video clips:

 

[DoubleWasp]

Wow. That is quite a noticeable noise.

 

[wag123]

That is not piston slap, a rod knock, or piston pin knock. It sounds mostly like cam/lifter/valve train noise to me. It also sounds like there is some exhaust leak noise mixed in.

 

[vinu_neuro]

What oil filter are you using?

 

[Dirty_Howie]

Originally Posted By: wag123
That is not piston slap, a rod knock, or piston pin knock. It sounds mostly like cam/lifter/valve train noise to me. It also sounds like there is some exhaust leak noise mixed in.


Do you think any of those things (except the exhaust leak) would show in the UOA.

All LS7 make valve train noise. But there is an additional wierd clackety-clack noise in there that you can hear if you listen for it.

DH

 

[wag123]

The clackety-clack noise you are hearing is probably the exhaust leak that I'm hearing. Does this car have aftermarket headers on it?

 

[buster]

Interesting...have you tried different gas?