Pic of Burned Piston - Why??
Thread Starter
On The Tree
Joined: Dec 2003
Posts: 109
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Originally Posted by blu00rdstr
All you guys are barking up the wrong tree!!! 
It's burning oil that causes knock, and it's coming in the PCV system. Oil drawn in under vacum seeps along the intake floor, pushed back by air flow and g-forces to the last runner. Guess which runner this is?
Us FI guys use an oil catch can and disconnect the PCV from the intake.
It's burning oil that causes knock, and it's coming in the PCV system. Oil drawn in under vacum seeps along the intake floor, pushed back by air flow and g-forces to the last runner. Guess which runner this is?
Us FI guys use an oil catch can and disconnect the PCV from the intake.
Lots of people here seem to think it was too lean. It could also have been a faulty injector or an insufficient fuel supply. Then again it could have been a combination of two or more. Next time it won't be so lean.
One thing is for sure though this has been a very interesting and informative thread. I'm glad I started it.
One more thing. We found the strangest thing when the engine was disassembeled today. No serious damage to the block and the piston pin on #7 was seized.
But get this:
My engine had two different types of connecting rods in it. Four on one side look like I-Beam rods and the other four look like H-beam rods. Maybe since the 2004 model run was coming to an end GM was trying to get rid of some oddball parts. Sure was strange.
Originally Posted by racecar
13.6 is way lean at WOT. 13.7 is the stock AFR for economy and polution. That's why the stock PE mode at WOT goes rich to 12.2, it's to save the motor. 12.7 is the best for max HP. If you are tuned WOT to 13.6 and hit that with NO2, then throw in a spark knock,,, well we see the results here. You may make a few more HP by leaning out 12.8 or 12.9, but why risk it.
Dave
TECH Enthusiast
Joined: Dec 2001
Posts: 548
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From: Dublin, CA
Originally Posted by LeMansBlue04
Now that is interesting because the floor of my FAST LSx intake is covered with oil.
If you lost cylinder seven, the most likely root cause is oil from the PCV. Oil has low octane (can't prove it though, I googled it to death), and it does cause carbon build up.
