Flaking around the valve reliefs under a 175 shot. I am building a 331 all forged assembly and this guy is telling me to research the probe pistons i bought for it.?His motor would burn a piston about every four runs on what he termed as a "safe tune".
The "flaking" around the valve reliefs is because the pistons have a thermal coating on them? And the thermal coating is flaking off? Or is the "flaking" the piston material itself coming off or apart? 175 H.P. shot is not to much IF you have the timing set up right for that much Nitrous. I ran a 347 cid with 13.5:1 compression and 225 H.P. shot of Nitrous and the Probe pistons worked fine as long as we used the right fuel (very important) and had the timing right.
I would greatly appreciate any further explanation on this as I still have the option of changing these pistons out right now but once it's together it'll be alot more work. These are 2618-t6 forged aluminum part #14112-030 compression with a 60cc head will right around 12:1
With 12.0:1 compression and Nitrous you MUST use C-16 race fuel (VP Fuels). If not expect detonation problems regardless of the ignition timing of the engine. C-12 (112 octane) is not enough. It is not that the octane is not good enough, it is the burn rate of the fuel that will get you into trouble every time. C-16 is formulated for use on high compression Nitrous engines. I went through a very steep learning curve when it comes to high compression and Nitrous. Not one nitrous book or Nitrous manufacturer that I spoke to when I was burning up pistons and cylinder heads and gaskets, not one mentioned anything about using the right fuel. They all concentrated on ignition timing, and fuel delivery and quantity NOT quality of fuel. Every Book I read about building Nitrous engines, not one example of a Nitrous motor being built was higher than 10.5:1 compression. They all talk about the right Air/Fuel ratios to run and the right ignition retards to use, and the right plugs to use, what octane fuel to use, ect. And 112 octane is fine for a 13.5:1 compression engine, until the Nitrous hits! You may get away with using lessor fuel for a while, but it will kill your engine in the long run. After you have replaced pistons, gaskets, had cylinder heads eaten up, ect about a dozen times, it gets real old real quick. Once I made the switch to C-16, not only did the breakdowns stop, the car went .5 faster in the 1/4 mile! Best E.T. by the way was 9.76! on a 225 H.P. shot.
Unfortunately hindsight is always 100% which is what sux about it, however your experience is invaluable to me as I have never heard anything about fuel quality either, simply that timing retard and fuel quantity is of the utmost importance which I do not doubt. All these things are ingredients for longevity inside a nitrous motor. Bro I can't thank you enough you may have very well saved me thousands of dollars.
As far as the quality of those pistons are concerned you should not have any issues, but like mentioned above the tune has to be right. Too much fuel is just as bad as too little with N2O, both can lift a ring l;and if your not careful.
I had a 13:1 N2O motor with a Wilson 2 stage plate, and I recommend flowing the sytem to see what you really have for fuel pressure, and definitely use C16 or VP N2O fuel.