I have an aluminum lightweight master that I got from mancini @8 years ago. It failed and I need to get another. I have a 68 charger, manual brakes, mopar action 11.75 rotor swap front, stock drum brakes.

mancini website lists the MC, but two different bore sizes....what's better for my manual brakes, bigger or smaller bore?

for the life of me I can't remember what I bought so long ago, I have a vague recollection of calling them and saying "gimme" and I guess I got lucky. I will say that it always stopped the car very well...

Can you measure the bore size of the old one?

I could...but it's at the body shop...about to emerge from a 6 month vacation getting all redone. the shop owner called me today and said that he has been moving it around and the pedal is very mushy when you first apply the break. once it's pumped up it's fine...but not good enough in my book.

I was hoping to have it ordered and here before I get the car back.

Were the brakes ok when it went to the shop? Have you tried bleeding them?

well, I've been told a 1" bore MC is the default for manual front disc brakes, so you could go with that.

smaller bore will mean less pedal effort, but you also need to balance stroke volume to make sure you're moving enough fluid.

I did a bunch of math, calculating mechanical advantage from the pedal (lever), and the hydraulic advantange, and figured out that with a 7/8" bore, I would only need 50 lbs of "leg pressure" to get the maximum braking effort. armed with that number in mind, I called up maste power and being the brake experts that they are, convinced me I needed a 1" bore for the stroke volume needed for my disc brakes

so I bought the larger master.

then, later discovered that the POWER brake master was only 15/16" bore! I could have probably gone with the 7/8" and been OK!