Any benefit to swapping from the old cast iron reservoir master cylinder to a newer style plastic? I happen to have one from a 98 2500 truck I parted out that is in excellent shape. Assuming it will bolt to my 86 W250 booster will it be any advantage over the old?

 

NO benefit. Cast MC is probably 4 bolt too...

 

Actually the old cast one is two bolt and the pattern looks almost identical... I have a rudimentary understanding of hydraulics and I know that if the bore and stroke of the piston is different you could drastically affect the force generated at the wheel cylinders (for better or worse). I may just hold on to the one I pulled from the 98 and in the event my cast iron takes a crap I will swap it in and see.

 

i have been told that the aluminum cyls cant be rebuilt. but dont know for sure. the hydraulics works like this . i had a heavy duty d250 1982. it had 1 ton brakes. i changed the rear cyls from 1" to 7/8 and the rear stopped locking up. I.E. less power. if you change the front master cyl to a smaller size you will put less power to the wheel cyl, reducing over all lock up.