here are the pics of my motor after a 350 shot of NOS, when the ring gap was only set for a 250 shot.
7 broken pistons
6 cracked cyld. walls

mike

 

#8 piston

 

Very nice... I see you can break the expensive parts just as good as I bust up the cheap ones.....

 

holy shiznig batman

=[

the juice killed the beast

 

That sucks!!!!!!!!!!!

Well at least you know the rods are good for a 350 shot.

 

OUCH...


Poor pistons, that wasn't very nice of you...

 

Anybody ever wonder why those of us with some motor building experience will tell you that slightly too little ring gap is alot worse than a little too much??? That's what you're actually looking at there.... the rings heated up and expanded, and their ends butted, and after that the rest was just inevitable.

If you plan on running nitrous, build your motor correctly for it. If you plan on running N/A, build your motor for that instead. There's no "I want a 600 HP 350 and then I'll slap on 250 HP of gas" in the real world; this is what happens.

 

pretty sweet.

Did you learn anything?

 

lol i learned the motors that come with the car are probly not built as well as they are said to be. it was in the car when i bought it and had 300 miles on it. i know the guy at the machine shop that built it and he said he built it for up to a 250 shot . ring gap at .025" . wellllll the 250 shot felt good for a month or 2 (thats my smallest jets) so i went to 300 . 2 months and 1 headgasket later, i studed and o-ringed the new dart heads and thought what the h*ll try the 350 jets after all its only another 50 . only lasted through 1st gear and then i lost all power . oh well now i get to build my own motor , and it will be built to handle the 450 jets(if i need them)

mike

 

What RB said.

Wanna know how you cracked the block (if you haven't figured it out yourself already)?

The chunks of piston ringland that broke off went up into the combustion chamber and got wedged between the piston and the head the next time it came to TDC. This forced the piston to **** sideways VIOLENTLY in it's bore, smashing the piston skirt into the side of the bore, immediately causing a vertical crack down the bore. If you do some piston diagnosis you'll find that the piston skirts are slightly "barrel shaped" on any of the pistons that came out of a cracked bore.

Seen this kinds stuff before. Never pretty. Not much left to salvage out of the motor once this happens.

Check your crank and rods before you reuse them. They can appear to be in good condition but could have picked up cracks or gotten slightly tweaked in this process, too.

Your heads will need at least new valves and seats since a lot of the metal carnage got smashed between the valves and their seats the next time the valve closed- usually effectively "welding" the junk to the seats or the valve.

 

i wouldnt even bother with the crank =[

 

Yeah, I agree to have the crank and rods very well inpected. Those rods should be able to take some abuse, but given the way in which the pistons came apart and the pressures it saw bad things can happen. Hopefully your heads will be reusable.

I had a friend with a 408 (mustang) and the roller rocker arm ball came out. The rocker then acted like a valve spring compressor because the tip was pushing down on the retainer instead of the valve. Well, it made this really nasty sound and died on the road not long after getting it together. We pulled the heads and found the intake valve, broken of course, wedged into its seat sideways. The cylinder in that hole was just destroyed. The piston had some huge gouges in it and the rod was ever so slightly bent. The crank was okay, though. He ended up getting one of the same heads used from another friend, new pistons, and new rods (went longer), and a new block. The rod looked just fine to us but we took them to a good machinist for inspection and he determined the one was just bent and out of round on the small end. That whole experience just plain sucked. So the point you ask, get it all looked over just to be sure for next time 'round...

 

sorry for the late reply . had to go to las vegas for the AC Delco national convention at the Venitian; WOW !!!! the nationals drags were good to . none of the bottom end will be reused . the heads look fine could just polish the surface but will give them a light cut, the valves ck.ed fine after clean up . it will be an aftermarket block next year . i have plans now after talking to some tec people at the strip in las vegas

mike

 

nos doesn't kill engines stupid people with nos kills engines.



just kidding!

 

Now correct me if I'm wrong but wouldn't not o-ringing the heads probably save the motor? Instead of blowing the motor you probably would have just blown another head gasket? I'd rather replace head gaskets once a week than blow my whole motor

 

Probably not.

That damage to the piston most likely occured when the ring gaps butted up because of too tight a gap. That's not to say the engine was faulty, just not correctly setup of heavy nitrous use. I have very little experience with o-ringed heads, but I also have little experience with nitrous systems over 300 HP. The most NOS I have ever used was 300 Fogger on an old carbed car. I set up my rings on the loose side because I figured a little extra blow by was better than eating an engine...

Later