jetvette

I am sure I must be very late at researching Hypereutectic Pistons but a warning such as this scares me. Even at stock HP & CR's, these pistons would worry me. By the way, I am not trying to implicate KB at all, it's just that the warning was from their ad.

Direct quote:
"KB Pistons - Hypereutectic
Please Note: Our 40 yrs. experience has shown us that these pistons should NEVER be used with Nitrous, super charger or turbo's. They should also NOT be used with Stroker Applications because of increased piston speeds. A forged piston is recommended in these applications, remember hypereutectic pistons are still cast pistons."

JoeRags

stingr69

They are good for some applications but high RPM and Nitrous ain't one of them. Naturaly aspirated and sensible RPM are a better application for Hypereutectic pistons. For a HP driver or a HP touring car they will probably be a better choice.

Forgings cost a lot more and people pay for them - They take more abuse.

-Mark.

evalu8r

That's interesting since the majority stroker kits and crates motors are Hypers and 80 percent of those are KB's.

Chris

SanDiegoPaul

When I built mine, I used ALL forged - crank, pistons etc, topped off with 6 inch H-beam rods. I've never looked back. I don't have to worry about NONE of that stuff!

And I may just do one of these things in the future. I did make a fatal error - porting and polishing and spending lotsa $$ on iron heads, instead of buying aluminum ones. So even though the bottom end of my stroker is bullet proof, the top end may come back apart some day.

shafrs3

Wow, that must be a new addition the their web page. I've got instructions with my KB pistons giving special ring gap dimensions to utilize if nitrous will be used.

427Hotrod

I've been saying that for years...if you're going to run it, then step up to even a cheap forging.

That said, there are hypereutectics...and then there are hypereutectics..there is a big difference in quality out there. The new LS-7 uses hypereutectics and spins 7000 rpm....but Mahle makes them and I'm sure there is a lot of R&D that goes in them. But still, I want to see what happens when they start boosting and spraying them!

Look at hyper's as an upgrade over stock. Better than regualr cast, but a long way from a hi-performance piston.


JIM

shafrs3

There is no warning about stock cast (non-hyper) pistons. Are you folks saying you're better off using non-hyperuetectic pistons with mild shots of NOS?

shafrs3

Can you copy/paste the exact place on their site that says this, I'm not finding it. In fact, the online instructions still show the clearences need when using NOS.
http://kb-silvolite.com/downloads/KB...Automotive.pdf

birdsmith

I built my 350 with a Summit hypereutectic piston kit ('Sil-vo-Lite" was the brand name at the time but I think they're the same as KB now). Basically I decompressed the motor from 10.25:1 to 9.0:1 and put a moderately larger cam in it. Of course I don't push it; it seldom sees 5000 rpm but I run it on 87 octane swill with absolutely no problems,and so far has done so for 30,000 miles. It doesn't use oil, doesn't overheat and gets 16 mpg on the freeway. But obviously if I was gonna build a hotrod motor one of the first things to look at would be forged pistons- it would be interesting to see if there's anybody out there that's built a hipo (read:high compression, wild cam, nitrous, etc.) Chebby with these pistons- I see them offered on ebay with very high compression numbers so there must be some low-budget brave souls out there willing to take the plunge!!

427Hotrod

OH NO!! Cast is Cast.....cast doesn't like detonation. Nitrous and boost are much more likely to encounter it and it takes a very small amount to fracture a cast piston.

Cheap gas and too much compression will do it too.

Pistons are not a place to cheap out on.

JIM

pauvil

that's true, when they dope the pistons during the process it causes a sponge like effect in the metal, a turbo or supercharger and nitrous under those pressures will destroy them very very quick!!!

427Hotrod

Birdsmith..your combo will last forever like that. You're not pushing things at all. I built a motor for a buddy with them and they will last forever for him too. You just have to decide the application.

You see some in high compression for "claimer" motors for roundy rounder racing. They have to build it cheap because they may have to surrender it if someone wants it....but they use race gas in them too to keep them alive.

JIM

jackson

As 427Hotrod said: there are hypers & then there are hypers.

Most cars today come OE w/ hyper ... most intended for 87 ... and many (even 4-cyl) are pushing 10:1 static CR from factory (yes they have sophisticated FI & ECM).

No I don't like KB hyper ... look at em & you can see they're cheap made ... I do like Sealed Power/SpeedPro hyper and Clevite hyper ... I have not looked at aftermarket Mahle hyper but their OE hyper stuff looks good. BTW ... all ZZ4 and all GMPP circle track motors come OE with hypers ... gazillions of 'em running lotsa race hours with piston failure quite rare.

Also, there are forged & then there are forged ... basically most mfg offer 2 forged grades of forged alloy ... 2618 is the toughest but requires lotsa skirt clearance & is really only for racing ... and 4032 alloy & its sibling VM-75 alloy require less skirt clearance & are good for street/strip & most racing.

Frankly, I can't see the logic behind a broad prohibition of hypers in strokers ... I think the focus should be on stress ... and not on how far the piston travels. I'v built several street strokers w/ SpeedPro hyper ... no piston failures.

evil herbavore

Well since a set of forged pistons usually costs less (usually much less) than 500 bucks, I'd call it cheap insurance.

jetvette

Here's the link to the warning. We all should form our own opinion or interpretation of the link. After reading some of the responses to my original post, it appears there are Hypereutectic and then there are Hypereutectic It is obvious that quality is paramount and pistons are not an area to save $$$$ without strongly considering the outcome of using lower quality units.

I agree, just the shear numbers alone indicate a general acceptance of the Hyereutectic process - but the range of uses must be moderated - as in all things.

http://www.flatlanderracing.com/kb_hyper.html

I'm Batman

I've been leading towards SpeedPro hypers for the LT-412 project. Since compression won't be over 10.5:1, I think I'll stick with that plan.

James B

THis kind of scares me, I bought some -12cc KBs last week. Im planning to use vortec heads with 9.6:1 compression ratio and the crane 272 cam. I was planning on being able to run it to 6000 rpm. If im carefull to make sure to avoid detonation i should be ok. Im only looking to run about 350-375 horsepower.

James

shafrs3

Piston speed increases significantly when stroke is increased, and if piston speed is increased, stress is increased.

shafrs3

Ah, ok. This was not KB's ad, it was flatlander racing's opinion.

Clearly, there is some controversy over KB hypers, not the manufacturing process. What I do know is I've used KB hypers now for 8 years on a stroked 454. Engine is rev limited at 5800 RPM which puts my piston speed somewhere around 4500 ft/sec, if memory serves.