It seems like forged is better but why? I want find a rebuild kit and the Hypereutectic pistions are like 100 bucks less? kevin

Depends on what you are planning to do with the build. Hypereutectic pistons are good for mild to mid build and can handle a 150 shop of NOS. Forged pistons can handle a lot more. What are you trying to accomplish with the rebuild?

Its a LT1 and im just going to rebuild with a hot cam and little stuff for now but never any nos. Maybe later on put some big heads and a big cam but for now just simple stuff.
kevin

Forged pistons are stronger, but they are obviously more expensive, they also expand less and require more piston to bore clearance.
Hyper pistons are not as strong, but expand less letting you run tighter piston to bore clearance. A high quality hyper piston has some benefits. Tight piston clearance is one. They are also able to put more material in critical areas in a hyper piston, without adding unecesary weight, due to the casting process, So even though forged material is stronger than a hyper material, the casting process allows them to make up for SOME of the disadvantage.
A forged piston will deform in severe engine damage, but hyper pistons tend to explode. Which is one reason why they are needed in boosted applications.
Hyper pistons will last forever in just about anything, as long as it NEVER runs lean or detonates. That is somewhat easy to accomplish naturally aspirated, but can be a little difficult with nitrous or boost.
By the way, if you build a motor that needs forged pistons, TRW or speed pro forged pistons are not really of the quality you need. They are made of an inferior material than most other forgings, and are also very heavy.

Ok i will just get the hypereutectic ones. I was just looking on summit for the rebuild kit? Is that a good or bad thing?
kevin

imo the speed pro pistons are very good quality, i have used them for yrs. i use them in ls1 engines. currently my dd ss makes 490rwhp with speed pro hypereutectic pistons. they will pose no prob. as long as the proper piston to bore and ring gap are correct.
another engine i built with speed pro pistons is making over 700rwhp with a t76 turbo. its all in the installation and tune.

summit has the lt1 rebuild kit, i used this kit on my old 355 lt1. 030 over.
i assembled the engine to abuse it. slapped a t60 turbo on it with a fmu made 450rwhp, street racing, track, wheel stands, never went. sold the car running hard lol
they are enuff for your build. proper assembly, ring gap, and block machining is the key

Not really sure what you mean by that.

What I meant by that was, and this is a quote from the KB-silvolite website"The dThe design flexibility enjoyed by the KB series of pistons has an advantage over present day forging practices. The die for a forged piston must be designed so it can be easily removed. This limitation makes it difficult to make a light weight piston without sacrificing strength.

The KB pistons' utilization of the permanent mold with multiple die parts allows undercut areas above the pin hole and material distribution in the skirt area that stiffen the entire piston unit. The forged piston requires thick skirts to achieve comparable piston rigidity. A rigid piston rocks less in the cylinder and improves ring seal.

The forged pistons' thick skirts add weight. The design of KB pistons gives us the option to build the lightest pistons on the market.
And when I said I am not a big fan of speedpro pistons, I was refering to their forged pistons. The hyper piston is of very high quality, for that matter so is there forged piston, but because it is an inferior material than most other forged pistons, it needs to be in a class of its own, which is better than cast, but well below the quality of SRP, or wiseco, ETC.

If you go hyper, be sure to pay attention to the ring gap

If you ignore the mfr specs you will butt gaps and break ringlands which is where 90% of the bad feedback about hypers comes from