I'm working on a 68 Mopar big block for SCCA AutoX Cam class and want to know what folks think of hydraulic brake assist or keep it manual. I have Wilwood brakes front and in the rear. I have never used this type of system and need some input. If any one is running the system did you piece it together or did you buy a kit?
Kit

As general comment, with the Wilwood calipers, I think you will need strong assist. They have smaller than OE piston area and need plenty of line pressure like the Cobra style calipers I run on an E. It would be hard to get a manual bake setup to work well. It is hard even with the large area of the factory single piston calipers.

I upgraded to a double 8" booster and 15/16" master to get enough line pressure for full braking wihh my Cobra setup. I am considering "some day" upgrade to hydroboost for the more compact installation and additional line pressure capability.

We will see how mine works out. I bought 12.88" 6piston Wilwood fronts and 12.2" 4 piston rears. Wilwood recommended a 7/8" master with my manual brake setup. I want to keep manual as long as I can for the pedal feel.

What master do you have now?

The plastic reservoir the Chrysler Type 1 1/16 piston.

Hydroboost is a love it or hate it feature, when set up right many like the extra braking pressure it creates while others are happy with manual brakes. Its an expensive experiment that I am planning on doing when I get my care farther along. Tim

I have a HydraTech kit. http://www.hydratechbraking.com/

He sold me a kit minus master which I sourced at a parts store. It was a 1 1/8" 1980's Dodge D-100 or D-150 I believe.

From my understanding it is a gamble getting a junkyard unit but you can get a rebuilt one from multiple sources, maybe Rock Auto? You can get the master locally too. The master on Hydra Tech's site is #MC8144 http://www.hydratechbraking.com/mastercylinders.html

You have no pedal "feel" with a hydroboost. It will be next to impossible to modulate the pedal on the threshold of lockup. Do your calcs right, piston area for MC bore, pedal ratio, and you'll have phenomenal manual brakes.

This is the information that I was looking for. It looks like I need to start with manual brakes and I can see how it goes. I can look at the pads that have more bite also but.

I sent Wilwood what brakes I was buying along with details on the car. Intended use, tire diameter, weight, estimated weight distribution, pedal ratio, etc and they provided me with a recommended manual master. We will see how it works out.

I feel like

Where I need to be headed

Now there is some misinformation! This feel is really dependent upon the correct caliper piston diameters. I love this unit and have used on 2 cars that see the track regularly.

This could help you a lot with manual brake sizing.

http://www.jakelatham.com/radical/info/brake_calculators.shtml

Without knowing your piston sizes or the pedal ratio, I don't really know where you'll end up. It really depends on how much stopping force you want for the pedal force, but I am guessing you'd end up with a 7/8" master cylinder.

Using just general rules of thumb, I would start with 1g decel at 100 lb pedal force.

I ran my car with my plan of 6.25:1 aftermarket pedals, the cobra braking system, .45 pad mu, and 100 lb pedal force for 1g decel and ended up with a 3/4 bore master cylinder and about the same pedal travel as my current 11.75" cordoba brake system with a 15/16 master cylinder...which is mostly likable, but the pedal force for a good amount of decel is still quite high.

Yes, totally agree. On track regularly and it provides the best of both worlds for being aggressive at the track and cruising on the street. It will definitely let you know if if your pistion diameter balance is off, but all the more reason to get it right.