what to use to clean pistons in block.

[Goat Blower]

Tranny fluid in the oil is a decades old trick, I actually just used that again recently with a light lifter tick sound, cleared it right up. Hydraulic fluid actually has cleansing properties hence the cleaning, but it won't do anything for dirty piston tops. Actually running ethanol fuels for the last couple of years has kept my tops perfectly clean, but simply leaning out your AF ratio for optimum power does almost the same thing. Piston tops get corroded from running rich like the factory tune.