TPIs-10

so- i have been trying to decide if i wanted to go with hypers or forged. reading on here as well as a few other boards got me even more confused that when i started- some people love them- others hate them. it seemed to me like i was reading a lot of speculation rather than first hand experience. so- i called their (kb's) tech dept. i was telling him that i was building a 388 with a 6 inch rod- looking for around 11:1 compression and around 500 hp. i told him i just wanted to know the limitations of their hyper pistons. he told me that for what i was building a hyper piston was more than enough. he said he personally built a 302 for his mustang with 16lbs of boost- it is still running as good as new after 240+ passes down the 1/4mi as well as street miles. he was also telling me about a couple off-shore boats that they sponsored with around 1100hp- that where using a kb hyper piston. he told me that they are good to about 8k rpms (i wont be much over 6k), around 1000hp (i am planning on half that), and 12.5:1 compression (as mentioned above- i will be around 11:1). i know i have read these pistons arent a good choice for a power adder- but he gave a couple examples of them working just fine. and you also have to assume a good tune on these engines he was talking about- but still- i think i will be just fine. especially- for half the price of a forged piston. i also asked him about the issue of the piston possible failing because of where the ring/pin is located on a 6inch rod/piston. he told me- "go with the 6"- slightly better performance- and you will never have a prob with the ring lands- assuming you put it together correctly in the first place".

keep in mind kb also sells forged pistons- and the guy didnt try to sell me on those.

all that being said- i think hypers will work out for me. just thought i would pass this on since have been reading a lot where people are wondering the same thing i have been

F-BIRD'88

The trick to using KB hyper pistons is proper ring gap set up.

Its bigger than other pistons. When the engine is running the gap is normal. The piston crown conducts heat more than other pistons which expands the top ring more when under power, requireing a larger gap.

TPIs-10

as soon as i think i have it all figured out- as far as a rotating assembly- i get some info that throws it all off.

i was thinking- 9000 series scat crank, 6" 4340 scat (7/16") ibeams, and some kb pistons. well- the guy at the machine shop says to stay away from the 9000 series crank- says they are junk and i should get a 4340 crank. this guy does very good work- as has been around forever- so i would think he would know his stuff. but- this is the first time i have ever heard anything bad about that crank. i don't think i really need a 4340 crank since i am not planning on any kind of power adder- i am just building a relatively high compression n/a engine- around 11:1. thinking around 500 hp- does anyone think that 4340 crank is really necessary? from what i have read- i dont think it is?

*edit*
good tip on the ring gap- i have read that in quite a few places

five7kid

iTrader: (14)

The good ol' boy engine builder that did my heads says a factory cast 400 crank has done his Roots-huffed 383 with cast pistons just fine for pushing his 3700 lb '37 Chevy pickup daily driver/racer down the track for the last 8 years. He said the same thing about top ring gaps - make 'em bigger.

pasky

Im running a 9000 crank and i've heard nothing but good things about them. Im running 11.5:1 and my machine shop said their great cranks and he has one in his 383 track car. I wouldn't even worry about buying a forged crank until your gonna go forced induction. A cast crank will be just fine.

Everyones opinions differ.

Damon

I've used them in many of my engines (personal experience). Set top ring gaps per their directions, no exceptions. Mostly on street/strip nitroused applications, but the last few motors have been blower-equipped.

They're tough little buggers but detonation will still tear them up faster than a forged slug. Of course, any piston will fail if run in detonation long enough, but forged are still better than hypers when encountering detonation.

wesilva

iTrader: (35)

The ring gap is large, as others have indicated. This allows some blow-by when the motor's cold and could even be the case during normal temps if you gapped the rings for nitrous or a power adder. You might consider running the Total Seal Max ring package. The top ring of the Total Seal Max ring set is a gapless ring that is comprised of two thin rings set 180 degrees apart with in the single ring groove. Set both rings gaps as per KB's instructions and you still have gapless qualities because of the overlap of the two rings. Does that make sense?

The second ring and the oil rings are standard type rings.

TPIs-10

i think i am just going to go with my original plan- the 9000 series crank and kb pistons- from what i have read- as long as both are set up correctly i should be fine with 11:1 compression and not rev'ing more than 6200 or so.