Gentleman... I am building a 492 (4.290 bore) with a cast scat crank (4.250), forged manley rods (6.385), and I am looking at Hypereutectic Pistons. I don't plan to spray my engine( if I ever did it would be no more than a 50 shot) or take it above 6000 rpms. The trans is a M-21 close ratio and the rear end is a 3:55 eaton posi 12 bolt. This car is for cruising and maybe occasional strip time. Maybe a couple times a year. Am I going to be disappointed with a non forged piston? The 2 pistons I am looking at are the KB #KB398(dome) and the KB #KB284(flat). Which piston do I want? My heads are 1976 model 781 open chamber oval part heads that have had a 5 angle valve job. No porting as of yet.

Thanks so much for your time guys. You are the best.

Shahreyar Shafei.

First let me say I am not an engine guru. I did have a set of Keith Black Silvo lite pistons in my big block. predetonation ruined three of my pistons. They were chipped off the edges down to the rings. This ruined lots of other internal components. I know the problem was actually predetonation, but I have been told forged pistons would not have done that. The hypereutectic pistons are very brittle. Never again. My new stroked big block has forged ones for sure!

Same here no guru, but I know in KB pistins follow the ring gap instructions that are included with the pistons......

Hypers are hard pistons I've shoved a few through block before back in the dirt car racing days.....

i have heard the same thing as raiderjefe.
they are very brittle, more than cast pistons.
i run cast in the velle, and had lots of detonation, and they are still holding up.
if i were to do it again, i would only run forged.

sorry i couldnt help you more.

aaron

Hyper pistons are "OK" for a mild performance project although I personally do not care (or use) KB hypers especially in a stroker. Don't like the ring support setup.
Is there a Speed Pro hyper that would fit your application? Or consider the Probe line of forged pistons for not really much more $$.

All Speed Pro Hypers are made for stock 6.135 rods. I went with Speed Pro H693CP's in my 454 rebuild for the benefit of a tight piston/wall - but this motor was only intended to be a 500HP street motor spinning to no more than 6000. Also have alum heads, 10.3/1 CR, plenty of cam and a real good cooling system, don't expect detonation to ever be an issue. For the few $$$, I would go with forgings on a stroker.

OH you mean hyper-cracktics . POS PISTONS, i learned the hard way !!!!
if you drag yourself to buy hypers,get speed pro !
I f you dont want to rebuild another engine soon, get forged ,or hell even cast!

Shahreyar Shafei.

I'd run 'em. They hold up better than cast. If you go with the KB brand make sure that you follow the ring gap instructions to a "T".

Forged may be lighter and not that much more money.


Regards,

Mike

I never came to the conclusion of what was wrong with my 383, but with definately less than 1500 miles on the rebuild, I pulled my engine to start restoring the rest of the car, and tore the engine apart. I found several skirts broke off my KB hypers laying in the pan, can't remember how many. I can't remember for sure, but I never saw any excessive P-W clearance or necessarily a lack of clearance. I quick search back a month or so ago to my topic might say what I found. I wish I knew for sure. I'm determined to take the more expensive route and put a whole new internally balanced forged rotating assembly when it comes time, unless parts prices dramatically rise. Probably hang onto the remaining parts of the rotating assembly (all of it minus the pistons) and build up my 4 bolt block into a truck engine of some kind at some point. On the positive side, I never saw any signs of detonation on the tops with the high compression that I was running.

Hmmmmm, well it looks like I should go forged then. Anyone know of a set that is not 600 + dollars?

Hyper pistons ARE cast pistons. No matter what the sale spitch given they are still simply a CAST piston.
More silicone... Makes the material harder and more brittle. When they break, they BREAK.

I personally don't believe they are worth any additional money over a standard casting, there is some advantage to the style available, but for what KB charges, shop around and you will find a deal on some SRP's, Probes, etc..
Spend the extra $100-200 now and never worry about the pistons.

Also,
if you are building a 4.250 stroke BBC, the extra money for the 6.385 rod WILL save you on balancing. So just buy a new set of Scat I beam capscrews and be done with it.

Hmmmmm, well it looks like I should go forged then. Anyone know of a set that is not 600 + dollars?
Speed Pro (TRW) is probably the cheapest. Heavy, but cheap. Be sure to measure piston to valve clearance with those too as they aren't too generous. May have to get them flycut. Look in Summit and Jegs for typical prices.

Obviously with a stroker motor I dont know what your piston to valve clearance will be....with that being said the 454 .030 over forged TRW pistons Im using are L2349 and with 118 cc brings compression to approx 10:1. Think they will run you about 400 bucks. Hope this may help.

Shahreyar Shafei.

I'd run 'em. They hold up better than cast.

Mike

What do think a hyper piston are no matter how you look at its still a cast piston as we have had many calls and emails on broken Hypers pistons and its funny that we don't have that kind of calls on broken forged pitons. HMMMM.

Carl,

Technically, yes, they are cast.

However, when someone mentions a cast piston they usually mean the old O.E.M. cast variety.

I'm not saying that it's the case in every situation, but I think that hypereutectic pistons got a bad rap early on due to the often ignored requirement of larger top ring gaps on the KB pistons.

Are forged pistons stronger? Yes. Would I be afraid to use hypereutectics in an application where I will be "cruising and maybe occasional strip time..... a couple times a year" like Shahreyar asked? Absolutely not. We run hypereutectics into detonation purposely every day. I'm surprised how well they hold up.

Mike

Hmmmmm, well it looks like I should go forged then. Anyone know of a set that is not 600 + dollars?

The best price I've found so far is at CNC-Motorsports.com They have them all the time for about $525. SRP forged that is. I've bought a few things from them. They seem like a good company. In fact I think someone here owns the company......

Try this.....$517 http://www.cnc-motorsports.com/product.asp?ProdID=8659&CtgID=8210