ok noob question

i currently have the head off the car. should i clean the pistons? there is some build up on the top off them. what should i use?

 

I wouldn't. You don't want carbon getting down between the piston and bore or in the rings. It's just my opinion, I've never read anything that says don't do it.

 

If you were pulling them I would say go for it.

 

I have typically done this in the past with other cars and it has helped with pinging.. Just make sure you dont gouge pitts in the top.

 

Automatic Transmission Fluid is pure detergent. Soak a rag and stuff it in the bore for a few minutes.
When I was a kid, my dad would pour ATF over the bare valves with the engine running to remove build up and sludge. A little ATF the goes by the rings and into your oil wont hurt anything but you would probably want to do an oil change just to be sure.
Don't flame me guys, he was an excelent mechanic.

 

if you bring whicever piston youre claening up tp TDC, you can spray 'em clean with brake kleen. it'll eliminate the possibility of you accidently gouging the piston head. but then you'll have some leakage into the oil pan. but since you have the head off you can change the oil. or you can soak a wash rag with brake kleen and wipe the piston.

 

Or you put it back together and use something like BG44K which decarbonizes an engine while it's running.

 

If you are using brake cleaner you need to re oil the bore and rings as the brake cleaner removes it.

 

use scapel like dentist.

 

I think some 80 grit sand paper would do the trick. If that does not work try sand blasting it.

On a serious note, I agree with EK9, BG44, good product.