I have looked through the threads here and other info on the internet and I am not sure if they are no good for 500+ hp applications. Does racing fuel make any difference? Any one have some solid info ? Thanks, Eric
im my opinion, these pistons are not good for anything over 8 to 1 compression ratio. i lost 2 engines due to these pistons breaking apart from detonation. and i dont mean slight engine failures-the last one all iwas able to save was 7 connecting rods. when these pistons fail, it is a major fracture of the piston top and pieces go everywhere!! and this was in a measured 10.3 to 1 engine with 92 octane fuel at sea level. the slightest bit of detonation starts a crack in the piston tops and when they finally break apart it isnt pretty. the slight advantage of close piston to wall clearances (the reason i tried them) and good oil control is far outweighed by how fragile they are.
The hypereutectics definitely aren't a very forgiving piston!! I've also seen the aftermath of an exploded hyper. piston!! Not pretty - or cheap!! I'm pretty sure I've heard Jim Burek and other engine builders say that they've run these pistons on performance motors with success! I think there are several variables that MUST be carefully watched: Piston to Wall clearance - tight, but round (torqueplate) Ring end gaps - I believe they require more gap A/F ratio - (lean=death to the pistons/engine) Timing needs to be right on Until we get some reasonable priced (TRW) pistons, we had better figure out how to run these things! The other options (as you know), are either cast or high dollar pistons.
As far as the majority of Buick Builders I know of, and myself, we all shy away from that particular piston, as the potential problems with motors that are not in our control far outweight any benefits. In the real world even 10-1 engines detonate under some circustances, when the customer is playing with the jetting or timing. Or you get that far too common bad tank of fuel. It happens, and when I put a motor together, I consider worst case curcumstances, not best case.. Personally, from a business standpoint, just too risky for my tastes. I will stay with either a good cast, or true forged piston. JW
Ok, I have a set of KB hypereutectics in my nailhead, intended for mainly street use. These are 10.5-1 deals. Is it safe, or am I better off pulling them out now, cause the engine is still out of the car. ??? Mark
10.0/1 Mark I havre the Hyper u pistons in my 74 455 they are the 10:1 type. but actual compression is only 9.1 or 9.3 :1 and I have been running this engine pretty hard. with a lot of timing but i always use 94 octane. I also spent some time softening all the sharp edges of the pistion tops, in an attempt to prevent detonation. Joe
I think that the low compression usage will not be a problem, I was at 10-11 with mine with little to no octane fuel, made 5 passes and boom! Never thought about the fuel until afterward. So Sad. Put the SS balanced block with the B4B and 107 cam and went 11.95 at the same POS Lapeer Raceway a month later. The guy I got the hyperutetics from knew some one at Federal Mogul. and I probably could have got a couple of more pistons, but didn't bother. Had another motor built with BME pistons that has not let me down! 11.30-40s!
Thanks Joe & Roberta. I'm going to talk to the machinist who built the engine next week, and get his input before I make any kneejerk moves. Mark
