Thoughts on why #5 and #7 pistons have chunks missing?
Thoughts on why #5 and #7 pistons have chunks missing? Here are the pics from blown motor:
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Could it be from predetonation? It happened at VIR, 71*, water temps were 203* and oil temps were 255*.
Here is my last dyno sheet:
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I thought it was a pretty conservative tune. Could it still be cracked ring and this is the damage I did on the 3 hr ride home? Thoughts?
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[/IMG]Could it be from predetonation? It happened at VIR, 71*, water temps were 203* and oil temps were 255*.
Here is my last dyno sheet:
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[/IMG]I thought it was a pretty conservative tune. Could it still be cracked ring and this is the damage I did on the 3 hr ride home? Thoughts?
It looks like the car went lean the piston is melted you can se the rings intaked in the first pick. My guess it went lean . Maybe you ran out of fuel pump under load
The dyno graph looks consistent a/f but can figure the # on that I am guessing the line is 12.5 so it looks good on the graph for mid 11's .
But your really testing the stock short block at that power level anyway.
The dyno graph looks consistent a/f but can figure the # on that I am guessing the line is 12.5 so it looks good on the graph for mid 11's .
But your really testing the stock short block at that power level anyway.
They look melted to me too. Detonation usualy looks like you hit the pistion with a ball peen hamer. (little dents every where) I'm preaty good friends with the service manager at our local GM dealer and two weeks ago he took me back in the shop to show me this durmax engine that had a bigger turbo and propane 30#'s of boost on cast pistions... 6 of them were cracked and 4 of them were melted like yours... It made me feel alot better about building a forged moter.
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They were a little dark and #7 was covered in oil
"Hard to tell by the pics, but it does look like detonation. You will know for sure when you pull the pistons out."
What should I look for with the piston?
My biggest concern is for the new engine and if this was a predetonation issue or an oil starvation issue. From what I gather it is a FI issue and not a road racing issue. It seems $500 for Accusump is pretty cheap insurance for a $9000 motor anyways. Thanks for the input.
"Hard to tell by the pics, but it does look like detonation. You will know for sure when you pull the pistons out."
What should I look for with the piston?
My biggest concern is for the new engine and if this was a predetonation issue or an oil starvation issue. From what I gather it is a FI issue and not a road racing issue. It seems $500 for Accusump is pretty cheap insurance for a $9000 motor anyways. Thanks for the input.
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