Hypereutectic Pistons vs. Forged Piston Slap.

[C O D Y]

There are many people here that have no clue about pistons. Some will say that I fall in that category, but I thought I would share my experiences.

I will preface this with the fact that I have two vipers and I stayed at a Holiday Inn last night. One viper with forged pistons and one hypereutectic pistons. Between the two there are over 100,000 miles on them and I can tell you what I have experienced.

FYI: 1992 to 1999 FORGED PISTONS / 2000 to 2002 HYPEREUTECTIC PISTONS

The reason people have labeled some motors creampuff is because of the hypereutectic pistons. Hypereutectic pistons are actually favored because of reduced scuffing, improved power, and fuel economy. The reduced thermal expansion rate allows the piston to be run with reduced clearance, which reduces losses due to gases escaping past the sealing rings.

Unlike forged pistons where you will get piston slap when starting a cold motor because of the thermal expansion

The term 'hypereutectic' comes from eutectic. Special melting processes are necessary to ‘supersaturate’ the aluminum with additional silicon content. Special molds, casting and cooling techniques are required to obtain finely and uniformly dispersed silicon particles throughout the material. This produces pistons that are very hard, thus brittle. For this reason they are great in naturally aspirated engines, but should be used with caution for 'nitrous', super- or turbochargers. Generally speaking, forged pistons are a better choice for high boost. After 20,000 miles on my hypereutectic pistons I haven't burn ONE DROP of oil and no piston slap.

Bottom line, if you are going to add forced induction, go with forged.... if not, you will get more life out of the hypereutectic pistons.

 

[PDCjonny]

I don't burn any oil either, with forged pistons at 23K.
Chuck has over 100K (I think, or close to it) on his forged pistons, including track racing, and he's none the worse. Is there some sort of study that has been made that indicates cast pistons last longer? From where do you draw these conclusions?

 

[C O D Y]

There was a recent article in one of the mopar mags about the hypereutectic pistons being used in an engine build up. I'll see if I can find it and why the builder used them.

As for my opinion... after owning 4 forged piston vipers (two brand new and following the break in proceeduce to a T) all of them burned some oil. It's well known that forged pistons will have piston slap on cold start ups too. I do not mod the engines in my vipers and I would use hypereutectic pistons if I was to build a motor.

 

[hemibeep]

Not sure about the material diff.
But my stock forged had a .020 offset pin to help avoid the piston slap.
When I switched to Ross, I saved 60 Grams each, and went with centered pins. I noticed more slap, but corrected alignment, and balanced the rotating assem that is 600 grams lighter.

I'll keep my Forged Ross set which outperforms and was $1300 cheaper than stock for the set.

Also I have file fit rings that are thicker on compression ring to help sealing. Not worried about friction loss, i.e. synthetic oil.

My 2¢

 

[DEVILDOG]

No oil burned here and whatever piston slap is I don't care. I'll stay with forged. My .02.

 

[C O D Y]

I'm just trying to clear the rumors of the Creampuffs. The fact of the matter is the Hypereutectic Pistons are actually HARDER than the forged pistons and that is the reason they are more brittle. If you don't force feed them they will resist wear much better!

The real creampuffs are the 96 and 97 cars with their soft pistons and smaller lift cams.

(That ought to get some ******* in a ***!)

 

[VIPER BAZ UK]

Now thats thrown a spanner in the works.......

2002 RT/10 with
Smooth tubes+KnN
Full borla system inc headers and HF Cats

to do list

Diamond pistons balanced to rods
Roe heads
708 cam
1.7 RR

All on stock fuel and PCM

Just read another thread and he seems to be OK no check engine light on same mods......

 

[PDCjonny]

I would swap mine out but I can't pronounce "Hypereutectic". Guess I'm stuck...
I believe my pistons can do whatever they want in the privacy of their own block, if they want to slap all night that's their business.

 

[OKViper]

i just like saying "forged" - especially around resale time...

 

[ndvipergtsr]

Wasn,t the creampuff name due to the non-lopey(708) cam and lower dyno #,s seen back when the nickname was given. I remember 410rwhp vs 440rwhp from threads. Jerry

 

[Joseph Dell]

The bigger issue w/ the pistons in the thinner ring-lands. See http://www.totalseal.com/howdoo.html for more details on ring lands.

Anyway, if the ring lands were thicker, then the "creampuff" could handle more boost. but being that it is thin, not so much as the ring lands tend to break apart.

just my .02...

JD

 

[Randy]

Wasn,t the creampuff name due to the non-lopey(708) cam and lower dyno #,s seen back when the nickname was given. I remember 410rwhp vs 440rwhp from threads. Jerry

Actually, I beleive the "creampuff" stock engines typically dyno slightly higher than previous models, possibly due the lighter pistons. However, its only slightly, and there's easily a 10-15 hp spread between difference stock engines anyway. But they certainly don't dyno *less* than the earlier "lopey" cam'd engines.

 

[C O D Y]

The real Creampuff cars (96 and 97) are not going to want to see this...... This is the mag article that I found. Not only do the real creampuffs not have the stronger pistons, the 98's and 99 car have the bigger cam! (I'm just stirring the ***)

In the article they built this 440 for good HP and long term durability. The 440 dyno'd at 476 HP. Just for the record, My 2002 GTS FE Dyno'd stock over 430 HP on a dynojet.

Here ya go.....

 

[KepRght]

thanks for the info cody.

related question

if i wanted to replace pistons and rings, is it ok to hone the cylinders in the car with one of those drill hone things? fyi motor has 115k and no sign of wear on the rod bearings. with that many miles, should i just re-use the same pistons and re-ring them, or is it ok to change pistons, or what advice do you give? new short block is 3500ish?

 

[Joseph Dell]

do it all in the car. no sense in pulling the motor. it is easier outside of the car, but not by much. and a drill-hone-thinggy works just fine. or a bead-hone, my personal favorite.

JD