Hypereutectic Pistons

Posted By: MoparMuscle

Hypereutectic Pistons - 08/13/09 03:56 AM

I've looked and called everywhere to try and find a set of forged std. size pistons. The only forged std. pistons are the old six pack TRW which would have been great but they are on intergalactic backorder. Everything else I found is .030 over and 600 dollars and up. This is a budget build for a temporary motor and the block only has .001 wear so I don't want to bore it.

Engine will have about 10 to 1 compression, 244/254 .555 roller, Stage VI heads, M1 intake, 950 custom Dominator.

Will be street driven some but mostly raced at the track.

What's the opinion on the KB Hypereutectic Pistons? Will they be ok for this?

Posted By: 70dusterjohn

Re: Hypereutectic Pistons - 08/13/09 04:01 AM

Sure there good pistions.. I'll tell you what the guy told me when I work on the tech line at summit. " they are a strong as a forged but light like a cast, but when they fail they break apart like a cast pistion" .. I belive that they are fine for a race car and or a street car. I wouldn't spray it, they seem to not stand up to well with the spray..

Posted By: 383man

Re: Hypereutectic Pistons - 08/13/09 04:07 AM

I have them in my 63's mild 440 and my sons 400. Both are street cars that get street driven much more then raced. The Dart's 400 has been together since 2004 and my 63's 440 has been on the road since Sept 2006. I drive my 63 alot and have raced it about 6 times in the last 3 years as I go to a T & T 2 or 3 times a year. But we run them hard and the KB Hyper pistons are holding up fine. My son shifts his short stroke 400 at 6700 to 6800 and I shift my .030 over 440 (446) at 6200. You just have to be sure and set the piston to wall clearance and the ring end gaps as they tell you. The top ring is very important to set it as they tell you. They can have some piston slap noise when cold but it goes right away as it warms up. My son and I are also on tight budgets and thats why we used them also. My 440 uses 906 heads and the MP .557 cam and has run 11.50's so far. My boys Dart has hit 11.40's in good air. Any way we have had great results with the Hyper pistons and my brother also uses them in some of his race cars and none have had any piston trouble. Ron

Posted By: MoparMuscle

Re: Hypereutectic Pistons - 08/13/09 04:23 AM

I've never tried them so ya'll made me feel better about using them. There won't be any spray and in the last motor I had this cam in it liked being shifted about 6000 so it sounds like they'll be fine.

Thanks

Posted By: ProStDodge

Re: Hypereutectic Pistons - 08/13/09 05:17 AM

Had a set in a Mopar 505hp 500" crate motor. Ran it on Alcohol and 13 psi ProCharger for a season - 9.40's in a 2800# Cuda, approximately 730hp. At the end of the season, dropped the motor in a Nitrous street car. 3800lbs 175hp of NOS ran 11.00's all day. Sold the car a year later to a guy that drove it home 300 miles to Alabama getting 14+ MPG (fat tire prostreet car.)

Yes I would recommend them for your application.

Posted By: mayhem148

Re: Hypereutectic Pistons - 08/13/09 05:21 AM

ive been told ups and downs on this subject. this has been covered several times. some people say there not worth the money(but i dont see why not) and some belive in them. there the perfect street strip car piston to me. good for light nitrous shot. they do shatter. if you cut one in half it looks worse than a cast piston cut in half. they look like swiss cheese inside. it kinda hard to explain. but what metal is there is stronger than the cast. i happen to be a fan of this design. when they first came out i think they were advertised as "stronger than cast lighter than forged". they are not as strong as forged in anyway. but as everything else in this world they have there ups and downs.

Posted By: qwkmopardan

Re: Hypereutectic Pistons - 08/13/09 06:26 AM

I'll take them over a heavy six pack piston every time. Make sure to wide gap the top ring like the instructions say or you will have major problems. Also being lighter than a stock piston the assembly will need to be balanced.

Posted By: moper

Re: Hypereutectic Pistons - 08/13/09 11:18 AM

The issue I see is the piston to wall clearance has to be tighter than the factory cast pistons. With any hyper this is so. So .001" wear already makes the bores too large IMO. Read the post about bulging up valley pans with regard to ring sealing. Hypers are installed tight because they dont expand. Put them in loose and they may be noisey, they will not allow the rings to seal as well, and they might end up rocking over time and hurting the skirts. If this is a "for the time being" I'd simply run what you have (stock, or upgrade and have it bored for proper fitting hypers... Then when you tear it down again, you can simply hone it to the proper clearance for the good forged units.

Posted By: emarine01

Re: Hypereutectic Pistons - 08/13/09 11:24 AM

We ran kb hypers in a stock stroke 360 and sprayed it with 125 shot every pass for a full year, just set them up with the proper ring and skirt specs for what you are doing, I have seen them fail from ring butting on chevies with a small shot, big mess, I would use them again over a real heavy piston for na use with more horespower than we made on spray <550>

Posted By: Crizila

Re: Hypereutectic Pistons - 08/13/09 12:05 PM

with all the above. To be on the safe side, I run the ring end gap about .002" larger than recommended ( top ring ). Although they recommend a tight piston to wall clearance,.002 - .003" will be ok. Minor spray ( 125 shot ) will be ok also.

Posted By: MoparMuscle

Re: Hypereutectic Pistons - 08/13/09 12:12 PM

Quote:

The issue I see is the piston to wall clearance has to be tighter than the factory cast pistons. With any hyper this is so. So .001" wear already makes the bores too large IMO. Read the post about bulging up valley pans with regard to ring sealing. Hypers are installed tight because they dont expand. Put them in loose and they may be noisey, they will not allow the rings to seal as well, and they might end up rocking over time and hurting the skirts. If this is a "for the time being" I'd simply run what you have (stock, or upgrade and have it bored for proper fitting hypers... Then when you tear it down again, you can simply hone it to the proper clearance for the good forged units.

The clearance was one of my concerns but after looking at the chart on their site it states .0020" - .0045" for bores over 4.100 in an na drag application with a top ring gap factor of .0075. It should be no problem to set it up in the middle at .003.

Posted By: 70Cuda383

Re: Hypereutectic Pistons - 08/13/09 12:16 PM

buddy of mine in the AF had one explode inside his small block chevy, he blamed it on the machine shop for setting the ring gaps improperly.

whats funny is this is the same machine shop that told me "you don't want to build a big block mopar stroker for your first engine...go build a SBC. you CAN'T screw those up

Posted By: JohnRR

Re: Hypereutectic Pistons - 08/13/09 12:50 PM

Quote:

Quote:

The issue I see is the piston to wall clearance has to be tighter than the factory cast pistons. With any hyper this is so. So .001" wear already makes the bores too large IMO. Read the post about bulging up valley pans with regard to ring sealing. Hypers are installed tight because they dont expand. Put them in loose and they may be noisey, they will not allow the rings to seal as well, and they might end up rocking over time and hurting the skirts. If this is a "for the time being" I'd simply run what you have (stock, or upgrade and have it bored for proper fitting hypers... Then when you tear it down again, you can simply hone it to the proper clearance for the good forged units.

The clearance was one of my concerns but after looking at the chart on their site it states .0020" - .0045" for bores over 4.100 in an na drag application with a top ring gap factor of .0075. It should be no problem to set it up in the middle at .003.

Are you are assuming the bore you have now is on the TIGHT side ?

I personally don't have any use for a Hyper piston other than an ASH TRAY and I don't SMOKE

Posted By: joelson6

Re: Hypereutectic Pistons - 08/13/09 12:51 PM

Quote:

but as everything else in this world they have there ups and downs.

a piston that has it's ups and downs, now that's funny

Posted By: MoparMuscle

Re: Hypereutectic Pistons - 08/13/09 02:03 PM

Quote:

Quote:

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The issue I see is the piston to wall clearance has to be tighter than the factory cast pistons. With any hyper this is so. So .001" wear already makes the bores too large IMO. Read the post about bulging up valley pans with regard to ring sealing. Hypers are installed tight because they dont expand. Put them in loose and they may be noisey, they will not allow the rings to seal as well, and they might end up rocking over time and hurting the skirts. If this is a "for the time being" I'd simply run what you have (stock, or upgrade and have it bored for proper fitting hypers... Then when you tear it down again, you can simply hone it to the proper clearance for the good forged units.

The clearance was one of my concerns but after looking at the chart on their site it states .0020" - .0045" for bores over 4.100 in an na drag application with a top ring gap factor of .0075. It should be no problem to set it up in the middle at .003.

Are you are assuming the bore you have now is on the TIGHT side ?

I personally don't have any use for a Hyper piston other than an ASH TRAY and I don't SMOKE ..

Not assuming, machinist miked with a dial bore gauge and the worst measurement was at the top of one cylinder and it was 4.3215.

Posted By: W2DODGE

Re: Hypereutectic Pistons - 08/13/09 02:25 PM

I have had good luck with K/B hyperutectic pistons 532 passes on my 318 runs 10.9s 11.0s @ 121 mph it was only supposed to be a temporary engine but runs so good the 360 still sets in the shop collecting dust I have other friends that have or are still runing them in street strip and dirt track cars and as much as 250 HP NOS

Posted By: Crizila

Re: Hypereutectic Pistons - 08/13/09 02:40 PM

Two things you gotta watch out for with hyper pistons - ring end gap and detonation. You wanna be sure you have enough octane rating to support your compression ratio / compression pressure and a fuel system that will deliver enough fuel at all times.

Posted By: JohnRR

Re: Hypereutectic Pistons - 08/13/09 05:10 PM

Quote:

Quote:

Quote:

Quote:

The issue I see is the piston to wall clearance has to be tighter than the factory cast pistons. With any hyper this is so. So .001" wear already makes the bores too large IMO. Read the post about bulging up valley pans with regard to ring sealing. Hypers are installed tight because they dont expand. Put them in loose and they may be noisey, they will not allow the rings to seal as well, and they might end up rocking over time and hurting the skirts. If this is a "for the time being" I'd simply run what you have (stock, or upgrade and have it bored for proper fitting hypers... Then when you tear it down again, you can simply hone it to the proper clearance for the good forged units.

The clearance was one of my concerns but after looking at the chart on their site it states .0020" - .0045" for bores over 4.100 in an na drag application with a top ring gap factor of .0075. It should be no problem to set it up in the middle at .003.

Are you are assuming the bore you have now is on the TIGHT side ?

I personally don't have any use for a Hyper piston other than an ASH TRAY and I don't SMOKE ..

Not assuming, machinist miked with a dial bore gauge and the worst measurement was at the top of one cylinder and it was 4.3215.

Did he do this with a torque plate installed ? How many miles on this block ?

Posted By: MoparMuscle

Re: Hypereutectic Pistons - 08/13/09 06:14 PM

Quote:

Quote:

Quote:

Quote:

Quote:

The issue I see is the piston to wall clearance has to be tighter than the factory cast pistons. With any hyper this is so. So .001" wear already makes the bores too large IMO. Read the post about bulging up valley pans with regard to ring sealing. Hypers are installed tight because they dont expand. Put them in loose and they may be noisey, they will not allow the rings to seal as well, and they might end up rocking over time and hurting the skirts. If this is a "for the time being" I'd simply run what you have (stock, or upgrade and have it bored for proper fitting hypers... Then when you tear it down again, you can simply hone it to the proper clearance for the good forged units.

The clearance was one of my concerns but after looking at the chart on their site it states .0020" - .0045" for bores over 4.100 in an na drag application with a top ring gap factor of .0075. It should be no problem to set it up in the middle at .003.

Are you are assuming the bore you have now is on the TIGHT side ?

I personally don't have any use for a Hyper piston other than an ASH TRAY and I don't SMOKE ..

Not assuming, machinist miked with a dial bore gauge and the worst measurement was at the top of one cylinder and it was 4.3215.

Did he do this with a torque plate installed ? How many miles on this block ?

Didn't use a torque plate to mike it but he will when honing. The motor came out of a small motorhome that only had 30000 miles on it. Bearings, cam lobes, pistons all looked immaculate very very clean inside. I was almost tempted to reuse the bearings they looked so good.

Posted By: dizuster

Re: Hypereutectic Pistons - 08/13/09 09:28 PM

I think the thing people often misunderstand about piston clearance, is that pistons are designed and machined undersized for a given bore.

If you have a 4" bore. The piston doesn't come in at 4" and you bore/hone for .005 of clearance. The piston is designed and machined to come in at 3.995" to give you .005" of clearance in a 4" bore.

So just because an old block used pistons with a ton of clearance, doesn't mean that you can't put a hypereutectic in it. If the bore is only over .001", it will only ad point .001" into the new piston clearance regardless of what brand/type of piston that was in the motor.

Of course pistons need to be checked for size, but machining and quality is so good now, you don't really have to worry about it.

I built a 340 with hypereutectic pistons in it a LONG time ago. It's got 500~600 passes, and God knows how many street miles on it.

I'd use them again for a street/strip build in a heartbeat.

Posted By: HotRodDave

Re: Hypereutectic Pistons - 08/14/09 12:35 AM

How strong they are depends on you definition of strong.

A hyper will handle more force before the metal deflects than a forged piston will, however while the forged one will just distort a little the hyper one will shatter like glass.

I had a set in my old 402 stroker and we machined the reverse dome off them and they were incredibly hard to machine. The machinist set a TRW forged in the lathe to show me how much softer it was and it was amazeing the differance. Because of the way a forged piston absorbs the deflection by bending it is more forgiving when it detonates, the hyper will shatter kinda like glass when it reaches its limit, the trick is to not excedd the limit by detonateing it

The harder metal deflects less under normal loading, that is one reason you can run a tighter bore clearance but the main reason is they don't expand as much because of the nature of the alloy. Because of that they will have more piston slap if they run the same clearance as an identicle forged piston, however if you run the tighter clearance that they recomend you will have less piston slap noise.

As for your motor I say run them, be carefull about the top ring gap in particular and be carefull on the tune to not detonate it and you will be fine.