Martilo,
I've attached some pics of my dial setup when I'm adjusting bearings. It's easier to do it on the car, because the weight of the indicator base will keep the rotor in one position.
As for the rx7 master cylinder. It is off a power unit (vacuum). I'm gonna take it off the booster and figure out a mount to bolt it up. The booster in this application (and others) uses engine vacuum on one side of a diaphram that is typically 5-10 times the diameter of the master cylinder. Therefore, with engine vacuum (8-10psi) helping, you have to press a lot less on the brake pedal. Some cars use a hydraulic assist and some newer VW's and Audi's are using an electric assist. Without a booser, most people find 50-65 lbs of force at the pedal acceptable. With a booster you may only have to give 10-20lbs of leg pressure.
Race cars never run boosters because the give a spongy feels and don't help with driver confidence. When you're running 340km/hr, you need all the confidence you can get. Depeding on your driving style you may want a larger diameter master cylinder that gives you a very short travel at the pedal, but will require more leg force. I personally prefer a short travel pedal. The increased pedal force doesn't bother me. If the lady of your house also drives the car, then she'd probably not like the pedal effort required to stop the car.
This rx7 unit I'm looking at adapting is available in 2 flavours 23.8mm and 25.4mm. It's a aluminum master and tandem just like the stock VW MC. I think the 23.8mm unit will work well with P-car brake conversions. The 25.4mm would require a strong right leg!
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