Well my brother was looking into his Mustang motor and decided to go with the supposidly cheaper lighter and stronger Hypereutectic Pistons instead of forged pistons with his 351 windsor... has anyone heard anything about these to confirm their strengths and their superiourity over forged components?

 

I think that Hyperutectic pistons have there place. They are cheaper, lighter and you are able to run tighter clearances with them because there size doesn't vary as much due to heat. I wouldn't say that Hyper... are stronger than Forged just because of the material used and process that they are created, but I do think that depending on application they can be a very good choice sometimes. You also have to take into consideration that your brother owns a Mustang too, so I wouldn't trust his information anyway, lol. I'm just kidding bout that last part, please don't take offense

 

Well, keep in mind that we are generalizing. For the purposes of my discussion, I am talking about good quality pistons of each type. With that caveat, you can think of pistons using the following categories. Cast, hypereutectic, and forged. The terms are really apples and oranges in that casting and forging refer to the method of production while HE refers to the material used. HE pistons are cast from a hypereutectic alloy. Different aluminum alloys are generally used to make each type of piston. The differences are related both to the manufacturing process and the material.

Without getting into the whys and wherefores, as I am not in the mood to write a book tonight, you can think of them in the following way. Cast pistons are inexpensive but not as strong as the other two types. They are made with alloys such as F-132 and are not used in performance applications. HE pistons are cast using a high silicon alloy. Here http://www.beckracing.com/page11.htm is a description of some of the characteristics of these pistons. High quality HE psitons, like the KB line, may be used in high performance NA applications.

The strongest pistons are high quality forgings and are made with alloys like 2618 aluminum. The are expensive and require larger bore clearance than HE pistons. A huge variety is available. For nutrous or forced induction, a high quality forged piston is clearly the way to go. However, a properly designed HE piston may also be used for lower boost levels and small nitrous shots.

KB is the brand of HE pistons I am most familiar with. Companies making high quality forgings include JE/SRP, Diamond, Ross, BME, Mahle, etc. Wiseco, Speed Pro, and TRW are modeately priced forgings that are also quite servicable if not used in the highest stress applications. Of course, to function properly the right piston pin must be used and appropriate rings with proper installation are a must.

Rich

 

Rich,
Just a nit for clarity. These two sentences may be confusing.

HE pistons are not a different "category or type" of piston. They are CAST and therefore can not be stronger then cast.
A better way to write this would be. That there are two categories; cast and forged, with HE being, arguably, the best of the cast type.

 

The sentences He wrote immediately following those clear it up pretty well


Incidentially, I saw a set of Speed Pro HE pistons this morning.. brand new & they looked like crap. I was pretty suprised at all the casting flash, lines & marks on the top.

 

The only thing i have found out throughout my day is when crap hits the fan a cast piston shatters, a hyper piston is a toss up between shattering and melting, and welp most forged piston that i destory are burnt and some times have a hole melted in them.

 

Detonation is the enemy, not your friend.

You need to get some professional help designing your engines.

 

Na i just need to learn bigger n20 jets are not better.

 

Na, ya need to learn to put enough fuel to it and pull 2* of timing per 50HP.

 

I believe our stock pistons are hyperutectic they take a heck of a lot of abuse for OEM parts. They certainly do have a place in perfomance motors just not all perfomance motors.

 

Stock pistons can take a lot of abuse, but I've not seen a single one whom did't fail eventually with boost over 6 psi. They seem to do a tiny bit better with NO2 and am virtually clueless on high output N/A.

My guess is at about the 420-430 some rwhp level you need go forged. Really good tuning could make me a lier, but for a real high performance car you really need forged pistons.

Rich.......... tired or not, that was a good post.

 

Hyper's are a toss up between forged and cast. Their good for moderate power/all motor apps. Better than cast-not as good as forged. I find that if a customer is willing to go for Hypers they will spend the little extra on forged. KB's accually require more P-W calearnce than forged.
Detonation will destroy any piston.

 

Hypereutectics are more wear resistant and dimensionally stable than sand cast or forged, qualities that make them attractive to OEMs for longevity and emissions. But they are more brittle than either forged or sand cast. Higher silicon content giveth, and taketh away. Not a big problem on a vehicle with computer control to help keep it out of detonation.

But on a carb/mechanical distributor application, they are much more dangerous. I had 2 hyper KBs let go on a 400 sbc while I was tuning the advance curve. Just a moment of detonation before I could let off the gas was enough to break ringlands, which then got smashed between piston top and head.... hasta la vista cherry casting #509 block. ..... I have had factory sand cast pistons survive much worse detonation, especially the ones in the original engine in my 71, which took an unholy beating before engine was yanked (still in good running condition) with >100k on it.

So my personal guide for engine builds: low perf or slight warm over, hypereutectics are ok, performance use = forged. Just to be safe.

So no, I would not say they are "superior" to forged, other than being stiffer and more wear resistant.

 

To me, a GOOD forged piston is the only way to go for high performance motor that will get used hard. I may be biased because pretty much all I deal with are race engines or boosted/sprayed setups.

That said, anyone know what the General is using in the LS7?

Rich

 

Best info I've read is 482 gm cast hypereutectic with coatings. Pin is very short compared to LS1/LS2. Generally a forged piston would be a tad heavier and fit looser. With titanium rods weighing a reported 464 grams, heavy slugs wouldn't be the way to get 7000 rpm durability. Remember this is a 100,000+ mile production engine, so noise, etc. isn't desired. Neither was it intender to be juiced. My guess is Mahle as a source, but more research is needed.

FWIW, much of the LS7/Z06 seems to be designed to accept more than the current 505 hp level. The 3 inch duals should support close to 600 hp. Bet the new driveline will also. Pistons would be an easy change if the engine grows another 100 hp or so.

My $.02