Using a smaller master cylinder on the JB7 brakes (13" drums) ok?

[Mattchu60]

I should start by saying - I upgraded to the JB7 brakes from a 3/4 ton (larger front calipers, rotors and 13" rear drums) 2 years ago on my truck which was originally a half ton. I did not touch the Master Cylinder, just replaced the flexible lines and everything bolted up fine.

The JB7 system came with a larger Master Cylinder and booster vs what my truck currently has. I recently came into possession of the larger MC and booster, but it appears the front/rear fittings on that MC are reversed in position on larger MC vs what I have now. This means to install it, I would either need to replace the lines from the proportioning valve to the MC, or bend the lines to fit the new positions.

So far, I have had no issues running the smaller MC, it seems to work fine. I do wonder though - if GM designed the system and thought a larger one was needed, maybe I should consider getting the proper one on there. Or maybe its pointless to switch them out.

The main difference I can see - the smaller MC has a 1-1/8" bore, the larger one has a 1-1/4" bore.

What do you guys think or know, I know little about brake system design, other than the basic concept of how they work.