I am bouncing around between running manual brakes (stock master cylinder with 4-wheel disc proportioning valve), or installing a power brake dual diagraphm booster and large master cylinder that I was going to use on another classic.
http://i5.ebayimg.com/04/i/05/df/92/24_1.JPG (http://cgi.ebay.com/ebaymotors/8-DUAL-CHROME-BRAKE-BOOSTER-KIT-LEMANS-CAMARO-FIREBIRD_W0QQcmdZViewItemQQcategoryZ33566QQihZ019Q QitemZ8027245218#ebayphotohosting)


The engine builder assures me that this motor will vacuum support the booster, but I am a little uncertain.

What would you do, or what would be best. Also, will my stock master cyliinder support the new system?

Which brakes are you running - stock disc/drum or 4 wheel disc? If 4 wheel disc - what type? The bore size of the calipers is really what determines the bore size of the MC you should use.

I personally prefer power assisted brakes, but a lot of folks prefer manual brakes. Some even prefer manual brakes because they don't like the looks of a booster.

I have to plead ignorance on the bore size. The rears are ford discs and calipers (9" rear end). The front are the CCP (CPP-?) kit from Matt's. I don't have any super-duper extra large disc kit.

I am a little worried about a ~500hp SBC allowing enough vacuum. I don't know if having the dual 8" booster helps the vacuum situation or not. I am CERTAIN that big 'ole chrome master cylinder is big enough though.

Here is my understanding on the subject: (hobbyist level here)

The smaller the caliper bore, the more line pressure is required to achieve adequate clamping force.

The smaller the MC bore, the more line pressure it produces.

If you use a large bore MC with a small bore caliper, you'll get a high firm pedal, but not enough line pressure to properly operate the brakes.

If you use a small bore MC with large piston calipers, you'll get enough pressure (maybe too much) but due to the volume required to move the piston in the caliper, you'll get a low pedal, or possibly it will go to the floor.

It's also important that the front and rear brakes are matched in terms of requiring close to the same pressure to operate them effectively. A mismatched set of fronts and rears won't usually work very well together. One or the other will be getting either too much or not enough line pressure. Sometimes this can be compensated for with and adjustable prop valve on the rear line. You can always dial out a little pressure, but you can't add pressure.

If you slap that chrome MC on there, at best it's a crapshoot. There is a "chance" it will work fine, but a bigger chance is that it won't.

If I were you I'd research the bore sizes of your calipers. Once you get that info, post it back here and one of the experts should be able to give you better advice on the choice of MC to run.