hey guys. im gonna put my motor i bought together, and i noticed that the pistons have carbon or something on the top.....whats the best way to get them clean again? and does it being on there matter? thanks

Just scrape it off with a putty knife being carefull not to gouge the piston. Then hit it with a brass brush. wash with soap and water and use compressed air to blow it dry.

Unless it is some exotic piston material, I used oven cleaner and it worked great...

Yeah- Easy-Off over cleaner works surprisingly well if the pistons are out of the motor- done that myself. If you're doing this with the pistons still installed just scrape it clean as best you can and then get ALL the crud out of the cylinder and ring area- especially the ring area. Last thing you want is clean pistons and scored cylinder walls!

+1 to Damon. If you do scrape them while in the block, use a shop vac instead of compressed air to clean up the dust. Don't blow the dirt throughout the block.

they are currently out of the motor.......ill probably be using some of that easy off oven cleaner to clean my block to be painted, so ill just use that on the pistons too.

Berrymans's Chemtool works GREAT. Buy the 1 gallon bucket and do them 1 at a time. It is the industrial carb cleaner stuff. Dip them in that stuff for about 30 minutes, rinse them off and air dry.
Be sure you lube the pins with oil thoroughly before reassembly no matter what method you use, you don't want the pins to be dry on fire up.

A trick I learned from some diesel guys is Cascade dishwasher detergent. Just soak them in a mix of Cascade and water overnight and they will look new. These guys get Cascade by the pallet, so they believe in it.

Jake, where is the warning? Berrymans is great stuff. The gallon can with the basket is real handy.

BUT, dont get it on you!!! It stinks to high heaven and wont wash off easily (the stink that is).