What size Vacuum reservoir to install

[Bihili]

My BB with the small supercharger has vacuum around 15 and the power brake booster is almost non-existent on the 8 inch double diaphragm booster.
I just purchased a modern GM vacuum pump and also a separate vacuum switch with hopes of improving my disc/drum braking.
The company selling the switch recommends a reservoir and a relay.

http://www.evwest.com/catalog/product_info.php?products_id=290

Is there a minimum size the vacuum canister reservoir should be,
how do you compute the correct size?

[markm]

15 inches should operate a decent booster, I believe my street driven Camaros have that or less with L-82 and 30-30 cams and PB. If I ever decide to switch to assist on 55/56 I will look in to hydro boost.

[NickP]

My BB with the small supercharger has vacuum around 15 and the power brake booster is almost non-existent on the 8 inch double diaphragm booster.
I just purchased a modern GM vacuum pump and also a separate vacuum switch with hopes of improving my disc/drum braking.
The company selling the switch recommends a reservoir and a relay.

http://www.evwest.com/catalog/product_info.php?products_id=290

Is there a minimum size the vacuum canister reservoir should be,
how do you compute the correct size?

If vacuum is the same as any other pressurized system there should be an amount of the volume used per depression of the pedal and what the evacuator can recover in what period of time. Most likely, I'm way off base but it seems like it's simple reverse logic.

[chevynut]

Bill, do you have PS? IMO I'd quit messing with the vacuum assist and go Hydroboost like Mark suggested. You'll get a lot better braking, imo, and it takes up less space than your booster. An Astro Van HB is only around $150 new thru RockAuto.....btw, I sell adapters. ;)

[Bihili]

Bill, do you have PS? IMO I'd quit messing with the vacuum assist and go Hydroboost like Mark suggested. You'll get a lot better braking, imo, and it takes up less space than your booster. An Astro Van HB is only around $150 new thru RockAuto.....btw, I sell adapters. ;)

Yes I have PS but I am not ready to throw away my chrome MC and Booster just yet.

Also I noticed the Treadle-Vac Power Brake Vacuum Reservoir Tank appears to be larger than the Jegs or Summitt 5"x 7" tanks.
How do I know what size I need?
If I have buy one and it is visible then I will get a chrome one but if I can hide it under the fender somewhere then I might even make one to fit.

[chevynut]

The smaller the reservoir, the more the pump runs...the larger the reservoir, the less the pump runs. I don't think there's much volume required to run the brakes. I imagine you could even run the brakes on the pump alone, without a reservoir, but it would run every time you touched the brakes.

You could probably use your existing MC with the hydroboost, if you go that direction.

[Maddog]

The pump will run when you touch the brake pedal regardless if you have reservoir or not. When you touch the pedal (move it) you crack open the valve on the booster and atmospheric pressure floods the booster which helps to push the master. Since you normally have your foot on the pedal for more then an "instant" all vacuum is pretty much gone and a tank doesn't help much if at all. A good pump will maintain 20" vac but is noisy if you don't install it in a insulated box-in the trunk.