I belive that warning is from flatlanderracing...not Keith Black.

Jeff

 

A hyper piston is actually stronger then a forged piston. It has up to 18 percent silicon making for a tough piston but hard to machine and also it was hard to keep the silicon suspended and not collect in lumps,
It is a very good cheap piston but fractures like glass if pushed to the breaking point, It can be fit very tight for good oil control and silent running on startup.
Unlike a forged piston which will give if overloaded it will not, it will break.
That said I have had a set in my nitrous 355 mustang for years and never had a problem. I intend to up the mustang to 426 cubes some time and I will use hypereutectic pistons when I do.

 

Will you be using KB's?

 

I have SpeedPro hyperuetectic pistons in my 406ci pushing 550 HP @ 6500RPM with no problems. I would run them again anytime in a street/strip motor.

I think we need to understand how our motors are run compared to an all out race motor or boat motor. An engine builder friend put if very well, and he was talking about a dedicated drag race motor at the time, when he said they were "prima donna's"

What he meant was the motor was blipped up to 6500RPM for a few seconds and that is it. So if you have a street motor you are going to see a few blips to 6500RPM and any half decent hyper piston will take that.

Now when you start talking about race motors ( circle track, high speed road course etc.) or boat motors that stay at 5500RPM for an hour then you need to start thinking about a forged assembly.

For mild to radical street performance hypereutectic pistons and cast cranks are the way to go unless you have money to burn

Click on the video under my sig and you will hear some hyper piston making 546HP @ 6500 RPM

 

Ive run hyper. pistons for years in alot of motors,including oval track motors,my nitrous mustang my nitrous 360 tpi motor and others without any trouble.

 

Many people using a stroker are going from 3.48" to a 3.75" (383ci) stroke. That amounts to less than 8% increase in piston speed. I'm not sure if I would call that significant.
An engine running at 5500 rpm instead of 5000 would see a greater difference in piston speed. One of the advantages of a larger throw is the increase in torque which is proportional to hp. The stroker engine needs less rpms to put put an equal amount of hp.

 

Norval..you don't need to buy any lottery tickets...you've already used up all your luck! :-)

Trust me, I've beat on a lot of cast pistons over the years and yes I've put a ton of nitrous on top of them and I gotta admit I haven't broke one. But I'm a careful tuner and pay attention to little stuff.

But I did lose a fuel solenoid once on a N20 setup and torched a piston before I got into second gear at the track. The neat part was the forged piston survived intact and didn't shatter and destroy stuff.

I just can't see the reasoning behind a set of cast anything pistons attached to a set of H-beam rods and a good crank, spend all the money to balance it etc. I mean we ain't talking big $$$ difference here and I sure like to have bulletproof stuff so I can keep extracting whatever power I can make and not worry about the bottom end.

I would use a cast crank anyday with a good set of forged pistons before I would do it the other way around.

But that's just me....I've seen too many shattered ones in other folks' stuff.

JIM

 

427 JIm, there has it right....

GENE

 

Norval..you don't need to buy any lottery tickets...you've already used up all your luck! :-)


Jim have you ever read the specs on the hyper pistons?? I have them and tensile strength is alot better then forged. Actually other then they don't bend/give they are superior to forged.
The ONLY advantage to forged is it will deform before breaking.
Cost?? A hyper piston here is about $16 each. A set of forged is $900.
Yes I went forged for the vet but feel comfortable with the hyper in the mustang.
You yourself said you never broke one.
Also hyper can be set really tight for better oil control and quieter running.
When they learned how to add the silicon to the aluminum and keep it suspended was a big breakthorough, that and new machining tools. The silicon really destroyed the old cutting tools.
For the dollar hyper are a great deal

 

They are wonderful pistons. If your rebuilding a 350 with it's little 3.480 inch stroke. You could run the motor to 7000 rpm for years. The KB pistons just have a feet per minute maximum. The longer the stroke the less rpm you can do.

I put on over 50,000 bad miles on a set.

 

A friend of mine is building a 383 with one of those KB kits. hyper pistons w/twisted wedge heads and a TPI intake.

I have my doubts about hyper pistons after reading about them. Im sure they are fine though.

 

Remember, there are also warnings on hair dryers not to use them in the shower. Doesn't mean they're bad hair dryers, just means the company is trying to protect itself from liability from mis-use and abuse of its product.

John

 

Not everybody consistently pushes the envelope with their equipment. If I were using my car to break class records I would without a doubt use all forged assemblies.

 

Check out the Mahle PowerPack Forged pistons. They are a high Silicon low expansion FORGED piston. Recommended cylinder wall clearance .0025 to .003. I think that is the same clearence as hypers. Sounds like the best of both worlds to me. I bought a set for my 383 build. Cost me $550 with ring set.

 

Hyper pistons (even KB) are "dollar for dollar" the best piston you can buy. Lets face it, the biggest problem with broken parts is bad maintenance or wrong application or simply put "improper installation". Everyone is quick on the KB bashing bandwagon just like everyone downed the comp cams. Reality is these are the leaders in the market in sales meaning there are more of thier product in our engines than any other. Thats why you hear more about them when they break. How many bears do you see dead on the side of the road compared to possums, squirrels, or other small animals? Not many cause there arent that many crossing the road compared to the other animals. BTW, you are more likely to crack the skirt on a forged slug than you are of scoring the skirt of a hyper slug, something to think about also, how many cars built in the last 15 years are using hyper pistons and still running in the hands of our teenagers now? I think we as a group have just taken things a bit out of proportion and are trying to compare these things to other types or brands that we do not have a equal representative sample to get an accurate comparison.

 

Norval..yes I've read the specs on them...and I agree with the part that technically speaking they are "stronger" than forged. I have to defer to your metalurgy knowledge for sure, but I put the "strength" discussion on the light of the application. I would much rather have a forged piston go "plastic" on me and deform a little than have shrapnel come apart and end up everywhere, rod punching a hole in the block etc.. I think a piston that "bends or gives" is a good thing compared to cracking and shattering.

GM wants to rev higher than a regular cast piston will go..so the next cheapest alternative is to use a Hyper AND control it's environment with complete engine management. If it detonates, it pulls the timing out until you add some gas to the tank. It has to SEE an increase in fuel level to believe that you added some better gas to it before it lets you have it all back. Then if it gets warm, it pulls timing again and plays with mixture to cool it down. Those are things the average guy doesn't have in our types of toys.

Next thing is GM and the aftermarket want to sell engines with a 350-400 hp that are cheap enough people will buy them. Hypers make perfect sense....they will live fine IF no one cranks timing too high etc.

As I mentioned earlier in the thread...if you are building a mild driver type deal and will make reasonable HP, I guess they will be OK. I'd use them in my pickup...maybe! But only if I wasn't going to tow a lot!

I've used the KB's and I do like the available features they offer for cheap prices. You can get a much more custom type piston for the price.

But I just can't get comfortable with the numbers of them I've seen shattered. Luckily they have not been in one of the motors I built...but I am REAL careful who I would say it was OK to use them. If I know it's going to get hammered on...it will get forged. I know Canadian prices are much higher..but you can get forged pistons for a small block down here for well under $400 a set. Cheaper heavy ones can be had for $250 max.

The 4032 SRP type pistons can be set at pretty tight clearances too. They don't swell as much and make a great tough street piston. That's what's in mine and they have lived very well. LONG way from $900 on price.

I guess we'll just have to agree to disagree...I like to over-engineer stuff so I don't have to mess with it...but I guess you can tell that from my driveline huh?

BTW- Yes I have never fractured one in one of my cars,,,but I always knew they were there and payed close attention. Nitrous was in the 150-175Hp range max. I still think I was just lucky.


JIM

 

That's quite true. However, long stroke (e.g. f/s) alone ain't necessarily the only limiting factor ... evidenced by virtually all OE BBC production motors built in last ten years (if not longer) have hypers and 4" or more stroke.

BTW ... on forged ... 4032/VM75 is the high silicon alloy ... 2618 is not high Si.

I recently got a set of wiseco forged 4032 for a motor I'm doing ... I would have used speedpro hyper if sp made the dish&CD&ringpak config I needed.

 

Agree....VM75 and it's cousin the 4032 is a high silicone forged version....makes a great street piston. Wears great and is tough enough to handle abuse.

2618 is what race pistons use....takes even more abuse....it will deform even more under adverse circumstances....but stays together. It needs much more wall clearances due to expansion changes.

The 4032's can be run down in the .002-.0025 range easily.


JIM

 

The Holley EFI system has provisions for knock control utilizing a GM sensor, can cut fuel to limit RPMs and with a wideband O2 sensor it can run closed loop and run whatever air/fuel mixture you desire at any engine load you desire, and it isn't even a high end aftermarket ECU.

Where can I read the comparison specs that you folks are referring too?