pistons

[71satellrunner]

Got a mildly built 340 in need of pistons any recomendations or comments? Feel safer with forged but so expensive. Are hypereutectics safe with no boost or nitrous? Also I found speed pro forged fairly cheap they any good?

 

[lewtot184]

i use hypereutectics in both my 440's. they're plenty good enough for a street car. just put them in correctly.

 

[71satellrunner]

Great. Kbs decent or what brand are you running? Ok to turn 7k?

 

[Meep-Meep]

Speed Pro forged are good so if the ones you are looking at aren't messed up then use them. Otherwise the KB's seem fine. I have a set in my 440 and I run it 6 K through the lights, so I'm thinking the shorter stroke and lighter piston 340 might be able to pull off some 7 K red lines. Do a piston speed calculation based on cast pistons, which have a limit of I believe 3500-4000 FPM.

 

[71satellrunner]

Happen to know the weight of the speed pros. or kb? I also found speed pro forged

 

[lewtot184]

the 340 kb's are 713g with a pin. the speed pros are probably stock weight. don't think of the kb hypereutectics in the same sense as a factory cast. the kb's have solid skirts (no slots or srtuts), and the aluminum is t6 heat treated. i use kb 184's in both my cars with no issues.

 

[Cazbah362]

I have a set of the hypers in a 440. Biggest issue I found when researching is if the ring gap is too close, heat builds and pops a portion of the piston? Never happended to me or anyone I know, but seems to be an issue in the great wide world at times. So build with this in mind. Have the speed pro forged as well, never an issue and reasonable.

 

[PoppaSmurf]

I've been using SpeedPro hyper's for years now in all my street motors, you should file fit your rings though...haven't had 1 failure in the 20 or so motors I've built..from the factory their within 1 gram of each other weight wise, valve releifs are nice, I chamferd the valve pocket edges before installation, and upon deassembly found there were NO carbon deposits at all...hadn't used the KB's did'nt care for the looks of the pin bosses...

 

[71satellrunner]

Happen to know stock piston weight?