ImBatman

I have been looking at my options for pistons to go in my 454. TRW forged LS-6 pistons are about $50 a peice. The KB LS-6's are about $42. I am not going to run nitrous on this car. I am just looking for good HP and reliability. The heads are going to be GMPP aluminum and should yeild around 10:1. What are the opinions on the KB hypers? :cheers:

Shark Racer

Now, this is coming from somebody who's just larning, so I'm sure ten guys are gonna jump and me and say otherwise, but I like the hypereutes. They're lighter and seal better than the forged steel. I say go for it! The forged *are* more durable, but not by a very large degree.

-Steve

PatsLs1vette

ive run them in anything from our 7600rpm circle track motors to my nitrous street motors, i have them in my new motor now.

gkull

I ran them for years and raise Hell with them. They have many good qualities. Like good cylinder to wall clearance. The KB's only have two valve reliefs to keep compression up.

Fevre

Seems I remember Norval stating that they are about as strong as forged but a little more brittle meaning that they will shatter rather than bend/indent. I had one shatter for unknown reasons in the eng that cam with my vette. It was not a pretty site. :eek: :cry

70BBvert

Just got my 454 back from the machine shop last week. They recommended a set from Speed - Pro part # 426cp. Coated skirts also - $320 for the set IIRC, yeilds about 10:1 compression also.

norvalwilhelm

Fevre. You have a long memory. Everything you said is true. I have comparison charts of forged vs hyper. and the hyper are actually strong then forged but like you said a forged is ductile, it will forgive and bend while the strong hyper is more brittle or if you over abuse it it might shatter. I personally thing they are a great piston even with mild doses of nitrous. I use them in my 11 second nitrous mustang without a problem.

GrandSportC3

I use Hyperutectic pistons in my 465HP 383 stroker and so far I haven't had any problems..

:cheers:

Olivier

American Boy

For the difference in price, you would be better with forged piston. They will give more durability and peace of mind. The forged piston are the old way of doing it with proven performance. They use a little more oil, may rattle on cold start but will last and last. The hyper are the new way of doing it, a little better in overall, but the durability is still to confirm.

An engine builder I talk with said that he had to redo a couple of engine that had hyper because of piston failure(in fact KB, if I remember correctly). Never happen with forged. He don't use hyper anymore.

Stephan

jackson

Wade:
For your stated purpose ... and regardless of price ... I think the hypereutectic has more pros than cons ... IMO I'd go w/hyper. If you haven't done so, do run the calculation using deck height, gasket, head cc, piston cc piston CD etc ... to get the right CR. Speed-Pro/TRW has several coated Hyper. Dunno if they're correct or not ... but here's some specs verbatim from Speed-Pro catalog:
H426CP: 1.640 CD, +10.5cc, dome, 1 VR---------
H581CP: 1.640 CD, +30cc, dome 2 VRs-----------
H625CP: 1.640 CD, -2cc, flat, 2 VRs------------
H626CP: 1.645 CD, -4cc, dish, 2 VRs----------
H693CP: 1.640 CD, +22cc, dome, 2 VRs-----------




[Modified by jackson, 1:22 PM 11/14/2002]

Yellow73BB

I'm putting the KB 257's in my BB right now. That should give me 10.3:1 compression. I'm replacing the 203s that gave me 9.1:1.

Make sure you gap the top ring properly. I saw a piston at the machine shop where the top ring wasn't gapped properly and it broke the top off the piston when the ring expanded too much and seized. The machinist told me that the Hypereutectics transfer heat a little better and so the top ring can expand more than with forged. I guess it isn't necessary to gap the second, but I am going to anyway.

joe73vette

As far as reliability, doesn't GM use hyper pistons in their HP motors now? Joe

ImBatman

Wow thanks for all or the replies and info. Out of 12 responses I see 11 to 1 in favor. I think I know which way I am going to be going. :yesnod: Now any suggestions on rings? thanks for all of the info. :cheers:

Ryan77

I plan on going with forged, they hold up to nitrous better, if I wasn't using nitrous though, I'd get the hyper's.

gdh

I am running a very similar setup as Olivier, have the Speed Pro and am very happy with them.

J75

I have the KB`s in my 383.No problems in 8000 miles.Summit recomends speed-pro moly rings for the KB`s, compatable expansion rates. :chevy

jackson

Wade:
Rings ... if you go with EITHER of the Speed-Pro below, a good Sealed Power Moly ring pn E233K ... or Speed-Pro Plasma Moly (std fit) pn R-9905 ... or same in "file fit" pn R-9590. My pick is pn R-9905. I've never used the "file fit" rings ... but I've always fitted each ring to each cylinder regardless of make/type ... even $20 sbc ring sets ... I've routinely filed 1'st & 2nd but never had to file oil rings.

Pins, press or float:
BTW all pistons below can have pins fitted either float or press ... EXCEPT H626CP as it is press-only. Factory rods are press, but can be bushed for float. For your stated purpose, press will be AOK. If you setup as pressed, DO NOT attempt to also use wrist pin locks (for float) that may be included with pistons.
H426CP: 1.640 CD, +10.5cc, dome, 1 VR---------
H581CP: 1.640 CD, +30cc, dome 2 VRs-----------
H625CP: 1.640 CD, -2cc, flat, 2 VRs------------
H626CP: 1.645 CD, -4cc, dish, 2 VRs----------
H693CP: 1.640 CD, +22cc, dome, 2 VRs-----------

joeveto

GM does use HP's in their performance engines, specifically the now dead F-cars. I'm not sure about the Vette.

I'm using them right now, and so far, I like them. From everything I've read, they are the best compromise between cylinder sealing and durability. Plus, no cold start knock. :)

fauxrs

BTW Steve, Forged pistons are aluminum - Not steel - no such thing as steel pistons in any GM motor - in any motor at all? I dont know.

Everything else you said is right on the mark. :cheers:

Clink69

I vote forged. I go for peace of mind and longevity, maybe over kill...

SRP forged in mine. All of my engine is forged, now everything else will break.

Chris :flag