DodgeM37

Dot 3, 4, and 5.1 are all glycol-ether based fluids. The difference is the boiling points - higher number, higher boiling point. The down side to these is they are hydroscopic; they absorb moisture. Which can cause rust and corrosion. Dot 5 is a silicon based fluid is is not hydroscopic. The Military uses this fluid since vehicles can sit unused for long periods of time. However Dot 5 can absorb air if not stored properly and can cause a weak petal. The two fluids are not compatible and when changing from one to the other the system must be thoroughly cleaned or bad things can happen.

Have several long block cranks out of the engines. Any tips or tricks to see if they are 237, 251 or 265?