Brake system pressure

[flyinlow]

Working on my Son's '70 Charger. Replace some brake lines while the engine is out. After bleeding I screwed the test gauge  in the divers caliper. 350psi STANDING on it. No power assist of course . Even without the booster I thought I would see 600-800 PSI ?

[mrob]

For what it's worth: on my 69 Coronet with manual disc brakes converted from a 74 A-body (with the stock size large single piston calipers) and a 1.032 inch master cylinder bore, I measured around 800 psi with normal pedal pressure and around 1200 psi pressing really hard on the pedal. FYI, my car stops pretty well with those brake pressures.
In my opinion, 350 psi sounds kind of low, especially if you were really standing on the pedal. Can you try again with the engine running and see if the booster will increase the brake pressure?

[John_Kunkel]

It all depends on the MC bore diameter. With a 1 1/8" MC, a 4-1 pedal ratio (typical for PB) and 100 lbs of leg pressure you'd produce a little over 400 psi of line pressure. Smaller MC bore increases the pressure.

Also depends on how much leg pressure you can produce by "standing on it". The older you get..........

http://www.wallaceracing.com/brake-master-cyl-calc1.php

[flyinlow]

I barrowed 19 inches of vacuum from my son's van via a 25 foot piece of fuel line. Max pressure with a healthy 30 year old standing on it was 900 psi. Better but still seams a little low?  The car was a 4 wheel drum brake car when we got it.  Added 10.75 rotors with pin calipers with Hawk HPS pads and 11/2.5  rear drums. Reused the original booster,  smaller diameter (Bendix ?). Do you need the larger diameter booster for disc brakes? Smaller piston MC?

[flyinlow]

I was using that calculator, how much does the booster increase the pressure on the MC rod ?

[b5blue]

Don't forget that funky lever peddle linkage under the dash. Ever try to stop a boosted Mopar with a defective booster?    (You can't!)