I've used this trick on my Jeep(s) for loosening up carbon deposits & cleaning out the combustion chambers without pulling the heads. Just don't do it on a vehicle equipped with a catalytic converter, it'll clog it up quick.
Dilute 2 pints of ATF with about 2 pints of water, put it in a jug with a good spout.
Run up the engine to around 3k rpms and have an assistant keep it there.
Trickle the mixture through the carb slowly (DON'T LET THE ENGINE STALL!).
After using up most of the mixture, run the engine at about 1k rpms for about 5-10 minutes. This will drive out any moisture remaining inside the exhaust system.
Afterwards, add some 2-cycle engine oil (about 2 oz) to a full tank of gas.
Oh yeah, if you have touchy neighbors, I don't suggest this trick.... It'll cover an entire block in a white fog and is noisy as heck....
I did this for the first time on my '77 Cherokee, and the amount of carbon that came out of that AMC 360cid was amazing....