[clint282cc]

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?

 

[clint282cc]

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...

 

[clint282cc]

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?

 

[clint282cc]

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.

 

[clint282cc]

what AF ratios were you running?

I don't have the equipment for that... I'm thinking the Injectors

 

[clint282cc]

its 100 shot. you dont need a tune for a 100 shot.

THE NITROUS DID NOT CAUSE THIS. it was the 30lb injectors w/out a tune putting too much fuel in the cylinders and washing down the walls.

 

[clint282cc]

Well I will just let you be then since you are obviously a master engine builder, what lasting a whole 5k miles on an engine before blowing it, and having blown the stock engine before this as well, you seem like you really know what you are doing. Keep up the good work! nethumb:

did you read the thread before you commented? we talked about the nitrous and we concluded it did not CAUSE the problem. it did help but 100 shot on a stock motor is not too much. the last motor i burnt a valve, i had too small of a fuel jet in it. this motor blew because of the WAY bigger injectors and the pcm didnt know how much fuel it was dumping in. dont come at me like im being some dick or smart ass. read what we are talking about before you comment...

and it begins

:waiting:

yeah, it had to start somewhere right? lol

 

[clint282cc]

like i said though after the first 50 miles it was running good. after the 500mile break in it was no longer running rich and i didnt use the nitrous till 1000 miles and the pcm leaned it WAY out from the first start up.

ALSO if it was running rich w/ nitrous, why would that be bad? if it was TOO rich and washing down the cylinder, that wouldnt be cause by the nitrous, the nitrous leans it out... correct?

 

[clint282cc]

Having a 408 built and not tunning it was a stupid mistake, especially the fact that you did not even have a wideband. If your going to spend the money to have a motor built you should plan ahead to atleast have a wideband.

Agreed. I was going to but ran out of money lol

 

[clint282cc]

It would be bad because you weren't running nitrous all the time now were you? Whenever you drove otherwise it was to rich which would wash down the cylinders. You're biggest problem was running with no tune at all and spraying on top of that.

I think the original start up is what scratched the walls and the nitrous is what screwed the prematurely worn rings. Only time will tell.

 

[clint282cc]

The pcm thought it had 19lb injectors when it had 30lbs. It puffed black smoke and ran like shit the first hour or two it ran. Then the pcm leaned it out and it ran awesome after break in.

It's a wet shot but its jot a rich jet. I burnt a valve on the past motor so I did bump it up a jet size but it couldn't have been rich

 

[clint282cc]

Thanks for the help guys! I'll update when I get it apart. After I do get it together w/ ported heads and long tubes and a tune! It will have a 200 shot and ill show u guys how a properly setup nitrous motor can last as long as a boost motor.