[Marv D]

Like said,, there are a few misconceptions in piston choices and popularity,, as the same goes for cranks, rods, and most everything else. Did you know MANY racers that use nitrous would much rather have a cast crank than a forged one. Reason being a cast crank is more forgiving and will 'flex' when it is hit with massive loads of pressure from the nitrous hit. A forged crank is HARD, BRITTLE and RIGID. It won't take flexing like cast,, it cracks. Don't read that wrong, few building a serious nitrous motor would consider using anything less than a true non-twist forging. BUT they would love to see the strength of a forged crank, with the flexibility of cast / ductile.

Now lets talk about pistons in the same light. Think of a hypereutectic piston as made out of Pyrex. We've all dropped mom's Pyrex bowl or dish and seen it turn back into the billion pieces of sand from whence it came. The hypereutectic alloy is just as brittle. (see picture above,, we found NO piece of the piston that was recognizable as piston except a small piece around the piston pin laying at the bottom of the pan) Hyper pistons shatter beyond comprehension unless you've ever pulled a head and seen carnage like that. That was NOT a nitrous motor. It was a normally aspirated 10.7:1 small block that was shifted at 6000-6200 rpm. The motor came apart at the 1-2 shift. What went first, the rod or the piston,,, I have my suspicions but it doesn't matter. WHERE is the piston???? If the piston was still there to guide the rod up and down the bore, maybe it wouldn't have gone through the side of the cylinder???

Now think of dropping a plastic bowl. It's soft, deforms, bounces and springs back,, won't take a lot of abuse before it crushes, but WILL take a lot of shock loading before it fails. That would be like a cast piston. You over do a cast piston and it WILL fail,, no doubt. But you miss the tune a little and it will survive, unlike the hyper that went south at the first hint of detonation.

Obviously the forged piston is like dropping a stainless steel bowl,,, it will dent your toe and the soft vinyl flooring before it cracks! We all know that so we won't even go there.

That's about as simple as I can state it. Something we all have done and can relate to. Hopefully not too simple as to sound stupid or condescending,, just trying to explain the strengths and weakness's of the different materials.

NOW,,, Thomas is talking about a KB hyper that 'ADVERTISED' 10.2:1 compression with a 64cc head. 10.2 with a iron head is risky with today's fuels,,, see picture above and remember, that motor ran Sonoco 102 motor octane fuel.

Also be VERY cautious in believing the 'advertised' compression on any site or from any manufacturer. How do they know what your deck height is?? how do they know if your going to use a 0.015" steel shim head gasket, or a 0.045" cheep builders composite gasket??? If you don't think that little 0.025" here and the 0.020" there doesn't add up to BUTTLOADS of compression you didn't know you have,, your fooling yourself. NEVER believe the advertised compression ratio MEASURE EVERYTHING your self (or have the machine shop do it) so you KNOW what your ending up with. Also did you know MANY of the KB pistons drop the piston as much as 0.040" down the hole. If you have a 0.025" normal deck clearance, and add the 0.040" from the KB compression height, and ALSO add the 0.040" for a normal FelPro composite head gasket,, you have a 105 thousands quench. I promise you that is going to be a detonating mutha with with that kind of quench. And let's not even discuss stacking all the errors in the other direction and ending up with a 11.8:1 motor that we thought was 10.2, and not feeding those hyper pistons enough octane.

End result is we have the potential to mistakenly throw a little detonation at the hyper (/ Pyrex) piston and near total engine destruction is the result. I'd MUCH rather throw $600 at a set of pistons and know I had a stable platform for as much power as I ever wanted to throw at them,,, than save $350 that could cost me 100% of all the rest of the investment.

That's my 2¢... but Thomas you sound like you have already made up your mind onthe build. And you SHOULD build the motor the way you want, can afford, or feel is right for you. I'm not saying if you use hyper pistons you WILL have carnage like the pic,, I'm not saying KB is junk, I'm not trying to do anything but offer some hind-sight in hopes it might help someone avoid some costly damage because they had never heard of the issue. That's all.