There's nothing wrong with the setup that you have... LOL other than the **** in the bearings. Get the oil galleries and everything cleaned out, new bearings and get it back together. It won't be the end of the world having mixed and matched pistons, that is just REALLY strange. I wonder what the weight difference is and if someone balanced that assembly, lol. What are your plans with your car? Now might be a good time to build a forged shortblock.... Seems like the popular thing to do! *wink*

 

those cleaner pistons are from a vette. the teflon coating on the side gave that away. the brown ones are the stockers. maybe something let loose in the motor then repaired before you bought it

 

The cleaner pistons are the revised pistons used in the newer LSx engines (i forget what year they changed them ). I would take the crank, rods and pistons to a reputable local machine shop and have EVERYTHING rebalanced. GM does a poop job on the balancing anyway then someone goes and throws different parts in there. Just my opinion....

Brad

 

I agree with ForceFedHP. Have everything balanced and checked. It is not worth blowing up your new motor because you skimped on a couple hundred bucks.

 

If your going to have it rebalanced...might as well spend $300-350 on a set of Probe forged pistons....they are pretty cheap and a quick upgrade for not much.
and some ARP rod bolts and your good to go 600 rwhp.
Then get it balanced

 

You read my mind

 

I womnder if maybe the previous owner took it back complaining of "piston slap" and they replaced some of the pistons with the newer, upgraded pistons? Just a wild guess. Very strange. I am just trying to figure out why someone would only replace 5.....sounds like a dealership move...lol.

 

I had to replace a rod piston combo on a 1995 318 chrysler because of hydro lock before. Piston, rod, and ring combo came all together. The rod had been bent so I got the entire assembly. Maybe something similar happened to yours?