As long as you are not putting the carb in there, you are good to go. I use straight prestone (Do not use water dilluted antifreeze). I remove rubber orings and carb's on other engines and that is all. I let it in there for a day. My crock pot will not boil the antifreeze. Make sure your crockpot does not boil the antifreeze either since that will stain the aluminum. The engine will come out like brand new.