Please help me confirm master cylinder choice

[Northern Goat]

I currently have a Wilwood disk brake kit with 13 inch rotors (front and rear) and the SL6R calipers (front) and SL4R rear, for my 1970 GTO project. I will be upgrading the front rotors to 14 inch, but I think this is irrelevant. I will also be using a 9 inch dual diaphragm booster and I need to confirm my master cylinder specs before ordering. I am looking at a master with a 1inch bore, the Front ports are listed as 12x1 BBL and the rear as 11X1.5BBL (not sure what the last two specs mean). Can anyone help to confirm whether or not this master will work well with my brake set up? Also do I really need to run a proportioning valve? Would prefer not to if I can get away with it. Just another connection that can potentially cause issues.

[Apogee]

The outlet ports on the master cylinder are ported for M12x1 and M11x11.5 ISO bubble flare fittings. I'm not sure which part of that you don't understand, however the "M" stands for "metric" and then the two numbers are the nominal thread diameter and thread pitch in millimeters. It sounds like you're looking at running a 1993-2002 F-body master cylinder if I had to guess.

As for an adjustable proportioning valve, I would suggest running one in any well balanced brake system since they allow you to get more performance out of the rear brakes in less than full-deceleration stops, which tend to be the majority of them in a street application. Can you run without one? Yes. Will you potentially have premature rear brake lockup issues because of it? Yes, more than likely IMO.

Tobin
KORE3

[Northern Goat]

Thanks Tobin. Will take your advice, as you are obviously more versed in this arena than I.