So I had a bit of blowby...

[XfireZ51]

I have datalogged my car enough to know that I don't have detonation. The top end timing doesn't induce any detonation. In researching this, I came across
this video by Hastings in piston ring failure.
https://youtu.be/3GbXxf435N4

One of the causes listed is "lugging" the motor. During some datalogging sessions, I have "lugged" the motor intentionally. Sometimes 6th gear at 900rpm
as a way of gathering readings on VE cells not typically used in normal driving.
So I'll be avoiding that in the future. Why just #7?

[LGAFF]

https://www.bing.com/videos/search?q...7D&FORM=VRDGAR

[XfireZ51]

Thanks Lee. Very interesting. I don't typically floor it in 6th and low rpm, but a a prolonged deliberate lugging of the motor could be the culprit.

[efnfast]

Well, I'll be avoiding lugging the motor a lot more. Thanks Dom.

[XfireZ51]

So a bit of an update. A couple of "while you're theres".
Replacing clutch disc and rod bearings. In the course of diagnosing the the cracked compression ring, Pete removed the rod end. He found the top portion of the bearing to be worn to the copper while the bottom end appeared to be fine. No issues w the rod journals. He surmises that this may have happened at engine initial startup. The motor came out of the 92 Aqua ZR and was a service replacement to the original motor. Pete suspects that since the service motors may have sat for some time, the top portion of the rod bearing had drained of oil, and startup of the motor without proper pre-oiling may have caused the wear.
Also, I am replacing the stock LT1 clutch disc I have been using. I have suspected that possibly the clutch could be slipping at top end after having done a series of mods that should have resulted in an increase of trap speed. Instead the trap has remained relatively flat and really isn't indicative of the power the motor is making. The disc we have removed shows signs of wear and is pretty thin. Replacing it w Centerforce sprung hub which has more "meat" to it. As you can see in the attached pics, the CF disc utilizes more of the area in the center to increase friction surface and several others like the way it works with their Fidanza FW.

[RichS]

I ran a Centerforce clutch in the GS before swapping to a auto. Drove like stock, pulled 1.5x 60's with it.

[GOLDCYLON]

Originally Posted by XfireZ51

So a bit of an update. A couple of "while you're theres".
Replacing clutch disc and rod bearings. In the course of diagnosing the the cracked compression ring, Pete removed the rod end. He found the top portion of the bearing to be worn to the copper while the bottom end appeared to be fine. No issues w the rod journals. He surmises that this may have happened at engine initial startup. The motor came out of the 92 Aqua ZR and was a service replacement to the original motor. Pete suspects that since the service motors may have sat for some time, the top portion of the rod bearing had drained of oil, and startup of the motor without proper pre-oiling may have caused the wear.
Also, I am replacing the stock LT1 clutch disc I have been using. I have suspected that possibly the clutch could be slipping at top end after having done a series of mods that should have resulted in an increase of trap speed. Instead the trap has remained relatively flat and really isn't indicative of the power the motor is making. The disc we have removed shows signs of wear and is pretty thin. Replacing it w Centerforce sprung hub which has more "meat" to it. As you can see in the attached pics, the CF disc utilizes more of the area in the center to increase friction surface and several others like the way it works with their Fidanza FW.

Is that the Camaro clutch disc Dom ?

[XfireZ51]

Originally Posted by GOLDCYLON

Is that the Camaro clutch disc Dom ?

The one I am replacing is a stock OEM LT1 clutch disc. So will be using the Centerforce. With 345s in back, I probably could use the clamping force.

[XfireZ51]

Below is a view of the top compression ring from #7. Also, motor is starting to go back together. Before Pete started, we discussed cc'ing the heads just to make sure we had all uniform chambers. Pete verified that they were uniform
40cc chambers. We did this on the suggestion of Marc H. Wanted to check if there was some other explanation for compression being overall somewhat lower on the driver's v passenger side banks. However, the FSM states compression should not vary greater than 15% from low to high cylinders. We're ok there (210 v 245). And FSM states that high end of adequate compression is 200psi. So we are over that by a significant number.

[WARP TEN]

Originally Posted by XfireZ51

Below is a view of the top compression ring from #7. Also, motor is starting to go back together. Before Pete started, we discussed cc'ing the heads just to make sure we had all uniform chambers. Pete verified that they were uniform
40cc chambers. We did this on the suggestion of Marc H. Wanted to check if there was some other explanation for compression being overall somewhat lower on the driver's v passenger side banks. However, the FSM states compression should not vary greater than 15% from low to high cylinders. We're ok there (210 v 245). And FSM states that high end of adequate compression is 200psi. So we are over that by a significant number.

Did the little pieces of the ring stay in the groove or did you have to go fishing in the oil for them?--Bob