[owensmat]

Hi there,
Writing from Detroit. I have a 1988 Daytona Shelby T2 block with a bathtub head. I bought the engine from an acquaintance and everything was completely rebuilt, machined and appears to be very well done. One question that I had....when replacing the pistons, instead of using stock replacement pistons, the builder used "Keith Black" hypereutectic pistons. What I've read about these pistons is that they are 30% stronger than the stock pistons and that the coating is some sort of heat deflector, helping them to last longer. While I'm told they are much better than stock, I'm also told that they're not as good as forged. I did call the Keith Black company and they tell me the pistons are very good and can easily handle the power that I'll be pushing them, which should hopefully be around 300hp at 16-18 pounds of boost. So I'm wondering what you guys think. Hypereutectic------junk or jammin??

 

[kermit]

I always thought that they were junk, from what I read from Donovan

Donovan's Dodge Garage

 

[speeduphoria]

most will say there junk and the stock cast are the best cast pistons available. I dont know how many of these people actually tried those pistons to actually say whats better or worse.

 

[owensmat]

Well, I'll hope they're not junk. The manufacturer said they've put twin turbos to them with up to 30 pounds boost. Of course, you have to consider the source. Thats why I thought I'd ask here to see if anyone here has used them, or knows much about them. They're in the car now so its too late, but I'd like to know what to expect.

 

[kermit]

Hyperutectic pistons for 2.2 and 2.5 engines

To be avoided at ALL costs on Chrysler turbocharged 2.2 & 2.5 engines. A snippet from the sealed-power webpage-

"Contains 12.5% or more silicon content. Special melting processes are necessary to ‘super-saturate’ 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. Our hyper-eutectic material is also being used in light and medium diesel engines to replace some of the eutectic pistons with iron groove inserts used for additional heat and wear resistance of the ring groove. Heat and wear in the ring groove contribute to groove ‘pound-out. In the Sealed Power hypereutectic pistons, the hard, finely dispersed silicon particles serve as ‘micro-inserts’ at the surfaces of the piston, especially in the surfaces of the precision machined ring grooves. The increased strength, heat and wear resistance provided by the high-silicon content hypereutectic piston material allows for elimination of the groove inserts in several piston applications."

Ed Peters, retired Chrysler failure analysis engineer did a study of hypereutectic pistons and this is what he determined..

1) Adding 8-16% silicon reduces excessive material waste by 25% during casting (reduced flashing)
2) Piston reject rate is reduced from 3% to less then 3/10's of 1 percent.
3) Added silicon creates pores and voids in the piston.
4) Piston cannot handle the thermal loads a turbo engine exhibits.

In short there is no performance benefit to making these pistons, it's all about reducing cost to MAKE MORE MONEY.

In my opinion you are good for low performance application, but if you are thinking about high performance, invest in a set of forged slugs.

 

[kermit]

Piston Coatings-

Dave's 16V pistons.

(Dave St. Louis's Turbo III pistons)

There are a variety of skirt and top coatings for pistons- The Teflon coatings on the skirts reduce wall friction, coatings on the underside help shed oil and ceramic coatings on the top help reflect heat back into the combustion chamber and help protect the piston in case of excessive EGT temperatures.

Note: A noted engine builder has warned me that coatings on the top of the piston may protect the piston but will reflect more heat back into the engine making it more prone to detonation.

I don't know a lot about coated pistons though, but this is what I've read.

 

[Shadow]

Keep your tune SAFE with conservative total timing and run proper fuel for the boost and they'll go 300hp @ 20psi no prob. Just DON'T let them knock.

 

[bfarroo]

The 2.2's are probably better than 2.5 as the piston design is better. I'm not sure the keith black pistons are any different than the parts store ones and I know GN guys run the hyperutectic pistons with a lot of boost, they just seem to be junk in our motors.

 

[ShelbyMopar89]

Here is a set for you. The good news is the other two are just fine.

These are the Keith Black ones you are talking about. They have no problem handling the HP, but as said before they can not handle any detonation at all. These have about 5 K miles on them at 23 PSI which actually worked out to five years for me because I do not drive it much. I went with Weisco this time around.