What went wrong? I have an NX wet kit on my 96 Z28. Well, after two bottles, I tore the engine apart and found a boken piston. Stock bottom end with 97000 miles and a Hot Cam. I have all the safty stuff. I think the end may have come one day at the dyno. If you search, last summer, I reported oil spu-ing out of the engine right after the dyno. I'm not blamming the dyno, that is just when it gave way. But my question is what went wrong? They new setup will be a 383 with LE3 heads and cam. All forged Eagle bottom end. Should I continue running the nitrous or sell the kit? I'll admit, I'm scared. What can I do to prevent the detenation and broken pistons? I want to run the nitrous but don't want to risk throwing away the $7 grand I've spent on the new setup. Any advise?

 

How much spray were you running? What was the timing? Spark plugs?
That could help us answer the questions you're asking, oh yah, what octane gas?

 

how much nitrous where your running? 150hp? More? I ran 150hp and the motor lasted but I wouldnt try anymore then that on a stock piston. Forged can take alot more abuse so your new motor will be able to take the Nos but still has limits.

 

I did a few 75 shots and then a few 100 shots. But only two bottles. Pulled no timing. Although I do have an MSD timing retard module, it wasn't installed. Spark plugs were NGK two steps colder than stock gapped for nitrous. All the safety stuff.
I've always run 93 octane since brand new.

 

Well every motor is different. I would always recommend pulling out some timing if you run Nitrous. When I was running the 150hp kit, I pulled out 6 degrees of timing, 4 degrees when running 100 octane gas. Motor ran for 40,000 on nitrous and never had a problem. Best run of 11:80's on a stock motor. I also was running 2 bottles but used the MSD timing controller to pull timing as soon as I hit the button. If your building a motor with all forged components, You will be safe then. But I do recommend pulling out timing when the nitrous is engaged.

 

I also forgot to mention I ran qround 18 bottles through the motor. The death of it came when I installed the supercharger but even then I didnt break the pistons. I also pulled timing with the supercharger and eventually the head gasket gave. Most of the time when a piston breaks, it is due to to much timing. Unless it was a mechanical failure (Rod let loose or a valve drops)

 

How did the plugs look when you were doing nitrous pulls on the dyno? Did you have a wide band on it? What kind of A/F ratios were you seeing?

 

I think I remember it was black. They did have the A/F ratio hooked up. They keept saying it was running real rich.

 

Where you keeping track of your fuel pressure durring the pass? Good pressure at idle/ part throttle does not mean it has enough volume WOT on the bottle (noticeable pressure drop).

 

Yes I do keep an eye on the fuel. I have a guage inside the cab. I did notice it does drop a psi or two at WOT. I do have a FPSS hooked up, so if the pressure did drop enogh, the nitrous would not flow. I'm sure it has to do with either octane not high enogh, no timing pulled, or fuel to nitrous ratio was out of wack. I'm sure it was all hooked up correctly. Maybe just too much abuse over the years. Also, when I pulled the pistons out, most of the rings fell to the floor in pieces.

 

How do the other pistons look?

I mean, it's possible that you simply had a piston suffering metal fatigue or that had microscopic fractures and the extra power pushed it over the edge.

Perhaps an examination of the other pistons can give you some insight into what was happening to the broken one.

 

The others don't look too bad but they do have alot of detonation signs. The heads really look bad. Number 7 piston is the one that broke and the piece that broke off just destroyed the combusion chamber on the head. It cut deep gouges in the head before desinigrating.

 

If you are building a forged bottom end 383 than it should with stand a lot. A lot like a 250-300 shot, I understand your fear of deastroying another motor but in your case something wasn't right with your stock shortblock, that is why it gave way to the 75,100 shots. Pull some timing and add higher octance gas when spraying in the future. I am not the best on diagnosing what happened to you previous motor. good luck

 

That is pretty odd man... you weren't running enough nitrous to to really cause much damage (normally).

 

I agree, not really enogh nitrous to destoy. Probably a pre existing problem.