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Discussion Starter · #1 ·
So let me preface by saying. We run a well known induction and tire limited SB nitrous class. Lets say generally 1150ish pph from the worst 4150 plate kit still currently in production and on the worst tire MT sells. We run a basic regular low port 23 degree 440 inch SBC on Q16 fuel in a 3000lbs C4 Corvette.

I don't know of many engine combos more forgiving, however when you're running the guts out of your stuff, bad things can happen. The best parts get hurt for the littlest mistake or unexpected problem and it doesn't take long.

Thats the case here. We were testing before a big event, going for a new PB and got it first hit right off the trailer. Second hit right after the high gear change the carb scoop departed from the car... we think maybe tire shake, as there was a noticeable spike on the DS graph... anyway the engine surged 2-3 times in high gear before my driver killed the run at about 600ft...... 60 and 330 were marginally better and despite the early shut down that was the second best hit the cars ever made.

Back in the pit, I noticed the windshield was covered in fuel siphoned out of the carburetor. Also the logger showed no pan vac for a good majority of high gear.... We know what that means but lied to ourselves, didn't think alot about it and busted ass to build a new scoop so we'd be ready for Q1.

Q1 we pull up, do the burnout and it pushes the front main seal out pulling into the staging lights .... we back off the line, park the car and watch for the remainder of the race knowing either test pass was good enough to be the #3 qualifier (that stings the ego a little).

The damage was 3 pistons like this one more or less. Just enough to stick the rings....


Fluid Gas Automotive exterior Rectangle Aluminium


Tableware Automotive tire Fluid Alloy wheel Rim


Now I'm not butt hurt about anything other than lying to myself and putting a little bit of oil the track trying to make Q1 with a hurt engine.

Luckily damage to the engine is minimal. A couple new pistons and a little extra bore clearance resulting from the needed cyl hone will put us back better than ever for next season.
Will
 

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Discussion Starter · #3 ·
Did the log show the AFR lean out because of the bowl vents?
Interestingly the logger showed the opposite. Indicated AFRs went from 12.2ish to 10.0 very abruptly at the moment the scoop came off.... obviously it went lean in reality but O2s read strangely sometimes.... there might have been so much oil or whatever taking up oxygen in the pipe... then again the plugs didn't show that either.

Pan vac went from 15" to zero about the same time... it hard to judge the precise time each occurs in relation to each other because I log O2s, fuel pressure, nitrous bottle pressure, engine rpm, driveshft rpm and battery voltage on my Computech Data Maxx logger and I log ignition and pan vac separately on my MSD 7531.

From what I have been told, using the 7531 to log pan vac is not the most accurate solution.... but it works and I'm out of channels on the logger.

It's interesting to me that it couldn't hurt the pistons any worse than this. I've had problems on much bigger kits and turned pistons into molten blobs.... but apparently a Cheater Plate can't get that done.
Will
 
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