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Discussion Starter #1
so i built my 408, had it professionally assembled and with some of the best parts. ran AWESOME. had tons of power, it was great.

after racing a WS6 "and winning with the help of my 100shot" i had a miss. thought i fouled a plug, changed all that, concluded it was not ignition. plugged it into the scanner and it had all kinds of miss codes on all different cylinders.

so i thought i just burnt a valve because it had the EXACT same symptoms and ran the same as it did when i burnt a valve on my 318. so i gathered parts and planned on tearing the top end apart. well, after pulling the heads off and realizing the valves were fine, i see this





some pretty deep scratches on the cylinder walls and its almost on every cylinder. do you guys think this is my problem? time to rebuild the motor? WHAT HAPPENED?
 

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Back in black
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Well I dont know much, if anything, about nitrous..but was it tuned/setup for nitrous or did you just throw the bottle in and spray it?
 

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was you runnin air filter? did you have releifs cut in bottom of cylinders? you would not think a 100 shot would do that. looks like metal to metal. when you figure it out post results
 

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Do the scrapes all share a common side of the cylinder(not sure if that's one pic per cylinder or not)?

Looks to me like the piston got pressed hard against that cylinder wall mid stroke.
 

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Don't be "That Guy"
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or your shot of nitrous burnt/broke the rings? broken rings will leave scratches like that in the cylinder walls too. how deep is "pretty deep" you might be able to hone it out, put new rings in it, and be good to go. this is why I stay away from nitrous!
 

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NO2 = bad IMO

althought those scratches don't look too bad they should come out easy enought. they look like the rings were not prepped or installed properly causing them.
 

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Discussion Starter #7
Mopar pcm and. U don't NEED a tune for 100 shot.

Yes I had a filter

All the scratches are on the top side or intake side of the cylinder.

I think a hone will fix it.

They were nitrous/moly rings...
 

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or your shot of nitrous burnt/broke the rings? broken rings will leave scratches like that in the cylinder walls too. how deep is "pretty deep" you might be able to hone it out, put new rings in it, and be good to go. this is why I stay away from nitrous!
thats what I was thinking
 

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If it's intake side on the drivers bank I'd say you didn't have enough revs before hitting the cheater gas on your 4" stroker. If that is the case you could confirm by removing the passenger side head and checking for scratches on the exhaust side of those cylinders.

Intake side on the passengers bank... might be rings as said above. Uniform damage like that from debris through the intake is unlikely.
 

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lost in translation
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damn clint,,you burnt up one motor on nitrous,,and you go doing it again...live and learn brother,,live and learn lol
 

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Discussion Starter #12
It seems the scratches are on intake on both banks. I'll look again.

The last motor was a stock motor. This one is built for nitrous... I am learning, see?
 

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Don't be "That Guy"
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did you file fit your rings, or did the machinist? aside from running all forged internals, did you tell him it would see nitrous? NA motors and boost/nitrous motors require different ring gaps. when in doubt...wider is better. the only thing that's bad with wider gaps is more blow-by, but if you have a properly working PCV system, it'll suck those fumes out before they can cause any real problems (if it doesn't work, you'll pressurize your crankcase and create oil leaks, and contaminate your oil with exhaust faster...so keep it working!)

the benefits to slightly wider gaps FAR outweigh the negatives in my opinion. if your gaps were too tight for nitrous, the ends could have butted together causing the gouges you see, and it could also sieze the motor.

My money is still on burnt or broken rings from the NO2 shot. that, or...when starting the engine the first time, did you ahve any fuel issues? running too rich or not starting? another possibility is that you washed the cylinders down with too much fuel--reducing the oil on the walls which could also prematurely wear out the rings and cause scoring.
 

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can you feel the scratches with your finger? does it catch your fingernail as you run it across?

hard to tell in your pics, but they really don't look THAT deep. I'd pull the pistons, hone the cylinders and re-ring it.
 

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If it's intake side on the drivers bank I'd say you didn't have enough revs before hitting the cheater gas on your 4" stroker. If that is the case you could confirm by removing the passenger side head and checking for scratches on the exhaust side of those cylinders.

Intake side on the passengers bank... might be rings as said above. Uniform damage like that from debris through the intake is unlikely.
I've banged mine out of the hole with a 150 shot countless times and my cylinder walls don't look like that, even after 60,000 hard miles.

I'm thinking it may have been tuned super rich and the extra fuel washed the oil coat off of the cylinder walls. Either that, or the ring gap was set too tight for nitrous.
 

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Discussion Starter #16
I bet my 30lb injectors had something to do with it... it ran very rich for the first 50 miles or so...

The machinist knew about the nitrous. U can feel the grooves but not really w/ ur nail.
 

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did you ever do a wet/dry compression test
 
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