I dont know much about hypereutectic pistons but i have always heard they dont last very long. I am wondering if i should order hypereutectic or forged with my rebuild kit. Im not planning on useing nitrous by the way. Any opinions? thanks!

 

.

 

Hypereutectic will be just as good as forged under street conditions. But if money allows, get forged.

 

hypers are stronger than forged and for stock replacement type pistons are lighter. they are also a lot more brittle and break when exposed to preignition. they also expand a lot more than cast or forged and require larger end gaps.

 

Here's some info I found at www.carcraft.com about Cast, Hypereutectic, and Forged pistons.

 

thaks that was helpful

 

Why do you think they're more brittle?

Here's a quote from Speed Pro, which are the pistons I'm using in my 350 build.



Are they lying about not needing larger ring lands and larger gaps?

AJ

 

i'd follow the manufactures recomendations, i never saw anywhere in what you posted to make me think they weren't as brittle as any other hyper. are you confuseing high strength for not being brittle? if so consider this take a coat hanger clamp it in a vise and smack it with a hammer, it'll bend. try the same thing with a file and you'll have at least 2 pieces. by most standars we'd all agree the file is the stronger of the two metals, and both are steel.

 

Hyper craps break when you boost them, spray them or get detonation.
TRW forged pistons can be found on ebay new for about the same price. I see no advantage to the hypercraps

 

hypers are lighter and disapate heat much better, and are stronger. they just don't live with detination or incorrect ring end gaps

 

The way you guys describe them makes it sould like they're worse than stock cast!!!!

That's true with any piston if you go beyond what they're made for. Hell, stock cast pistons can take ~125-150 HP shot of juice. Hypereutectics are good for more than that with ~225 being the norm. I don't know what the limits are of forged pistons, but it really doesn't matter if you get too much detonation. Any piston will fly apart if that happens.

Why do you keep saying that about the ring end gaps? That's so untrue. These aren't forged pistons. They don't swell under heat or contract while cool like forged pistons do. Forged pistons are the ones that you have to watch the ring end gaps with. Hypers don't take any more ring gap than stock cast do.

Granted, forged pistons are MUCH stronger than hypereutectic, but they're also MUCH more expensive. Hypereutectics have their place, just like any other automotive part. But you guys make them sound like they're inferior to stock cast pistons. Why?

You left out one minor detail. You have to hit the file A LOT harder to get it to break than it takes to get the coat hanger to bend. And I can bend a coat hanger back and forth fast enough to make it break from stress. Can you do that with a file?

AJ

 

not if the file and coat hanger are the same size, files aren't hard to break. aj you sure you've installed a set of hypers? all the ones i've used need 40% increase in end gap over stock, but i believe there are some hypers that will run stock end gaps, but i've not used them, and hypers do transfer heat a lot more than cast or forged, that's the reason behind opening up the end gaps.

 

the true test is to take a hypereutectic piston and a forged piston .... with one in each hand, drop them on a cement floor from the same height, say 6 feet.... U will know which one you want after that.... there really is no contest durability wise, I think you can live with 5 minutes of inaudible piston slap at idle in return for the greater amount of abuse they can take.

 

the forged are stronger for turbo or nitrous. but on the same note in comparison to a hypereutectic piston they are much heavier and dont expand into the cylinder walls as well... if you are natuarally aspirated with under 11:1 compression go with the hypereutectic otherwise go forged.

 

AJ....clifton? i live in onarga....

anywho, cast < hyperutectic < forged
that sums it up

 

Hypereutectic pistons are more brittle, its an inherent quality because of what they did. In general, materials that are stronger are also more brittle. Using the coat hanger example, thats sorta what a forged piston will do. It will deform rather than break right away. The strength limit is somewhere past where it starts to deform, making it a little more tolerant to abuse. A hyper piston when it reaches its strength limit just gives up and breaks.

As for the ring end gaps, that is all dependant upon the piston design and where the rings are. The only reason the hypers expand less is because the alloy doesnt expand as much under the heat its subjected to. This doesnt make it run any cooler or make it transfer less heat to the rings, it just means the material doesnt expand as much. Two totally different things.

Anyway, if you are planning on boost or nitrous, I'd recommend using forged pistons. Otherwise, the hypers will work just fine.

 

The coat hanger doesn't break from stress. It breaks because it gets work hardened and brittle. Like a hard hypereutetic are brittle, they will crack and break because they are hard.

 

my machinist tells me that hyper's expand alot less which is why they allow you to run tighter piston to wall clearances. hyper pistons are all i have ever used.

 

Now your understanding!

Stock cast pistons changed over the years anyway. In 90 they went to a lighter version. I think i would spray on a cast piston before a hypercrap piston.

Hypercrap are good for ONE thing. Tight tolerances that don't change. Thats it.
You can buy a light forged piston if you have the money.
I have TRW's I droped a valve guide in to the engine while it was running. Needless to say everytime the piston came up it smashed the guide between the head and piston. I drove it home. Rebuilt the engine and reused that same TRW piston. It had minor nicks it, nothing more. That was last year.
A hypercrap would have shatterd, went down in to the pan, went through the oil system, while the rod punched a hole in the block and destroyed the crank.

hypercrap are an all or nothing piston. They are together are they are not. Forged will distort before breaking.

 

 

WOW I provided useful insights based on actual experiance and you provided a 'rolleyes' smilie face.

Could you maybe add a 'doh' smilie face to back that up?

Or how about you take a solid peice of metal, put it in a cylinder and run the engine using a hypercrap piston. Tell me what happens when it breaks.

 

madmax,

Allow me the honor



And a cast piston wouldn't?

AJ

 

one for not knowing what you are talking about
two for being the second person in a row.

Wouldn't know what the cast, piston would do. Never said I did.
Would take it over the hypercrap ones.

I DO know my TRW forged pistons didn't break under that situation. I also know it was reusable.

 

So if you don't know if the cast piston would have broken, then how would you know that the hyper would, when it was a forged in the engine?

And I'm the one who doesn't know what I'm talking about?

AJ

 

Gee, bet you didn't expect such a food fight, eh? Go with the forged pistons. Look at it this way: with the total cost of an engine rebuild how much additional money do you need for forged pistons over the hypers? Not much.

How much peace of mind will they provide? A lot.

The ony time I wouldn't use forged pistons is if it was a totally stock 150hp V8 engine. Here not only would I use stock cast pistons I'd reuse the stock valves too.

RBob.

 

since it may be of use sometime i'll give you all a quick how to for testing metal brittleness, called a sharpie vee notch test. i piece of metal is prepared by milling to a square about 3 inches long with a vee notch about .125 deep in the center. it is placed in a fixture and a weight is droped on it, sort of like a sledge hammer on a pendulum there is a scale to read how far the hammer moves upward after it hits the test piece this reading is equated to how brittle or ductile the metal is. how hard the hammer falls is controlled as is the size of the test piece, often the test piece is frozen in liquid nitrogen. you might be able to better picture how a file and coat hanger would preform during this test and see that even thought the file would test much harder on a hardness test it would break much more easily.

 

The expansion of the piston has nothing to do with the required ring end gap. What causes a hyper to require more end gap is the fact that it reflects heat, causing everything around it to run at a hotter temp, which will make the rings run hotter and expand, necessitating a looser end gap. The reflecting of the heat is good for power output however. The less heat absorbed by the piston, the more there is in the chamber, which will create slightly more cyl pressure pushing down on the piston. Hypers work good for their intended purpose, but in a blown/turbo/nitrous etc engine, you have to be careful, as they will not tolerate any "mistakes" with the tuneup, and they will melt and/or break alot easier then a good forging. I used some hypers in the past in circletrack apps with very good success. Its all about the correct application of parts.
Bob

 

Yeah its called an "impact test"!

 

OK....

All you guys are right.

Hypers are useless.

They're junk.

They're a waste of perfectly good aluminum.

Cast stockers are better but forged should be the only thing anyone ever uses.

Forged pistons are the only ones that can be used with boost or spray.

A file is more brittle than a coat hanger.




There........ are all of you happy now? I agree with all of you. Is that what it takes to get you to STFU and make you think that you're right? If so, consider it done.

AJ

 

AJ
I could really give a **** less if you agree with me or not. Someone asked a question, and i was giving him the information i thought he needed. I at no point said they are junk, they just have limitations, much like anything else. And i will STFU when i feel like it. I dont need someone to "make me feel im right". I do engines for a living (extremely high end engines, btw) and have a pretty good idea what im talking about. No one here really got into a flaming contest with anybody, so the last post was a little offensive. If it was not meant to be, then my appologies.
Bob

 

well now that was fun, but i think it's time to let this thread sink to the next page.