power brake conversion question

[kurts704]

Converted my 67 k10 to power disc brakes with 80's 1/2 ton axles. I got a 72 power booster and master cylinder, with the 80's prop valve. The brakes work well, but if I stall or lose vacuum I have absolutely no stopping power whatsoever. I mean NOTHING. I'm fine driving it, but real nervous that if the truck stalls I'm screwed. Anybody know if something in this combination is no good?
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[LowGT]

Someone can chime in if I'm talking out my you-know-what, but you can put a check valve in the vac line going to the booster. Basically holds vacuum so you can brake once after the engine stalls. After that, you're hosed.

[shawno72]

Even if you lose the booster you should still have manual brakes. Prob will have to just about stand on the brakes but should be able to stop. If not then something else may be wrong.
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[Longhorn Man]

power brakes with no vacuum takes a LOT of effort to apply. These trucks seem to be worse than other vehicles. (it is much harder than a manual brake setup)
You need to test your booster. When the engine is first shut off, you should have enough vacuum left to apply the brakes with relative ease) 2 or 3 times. If the pedal goes 'hard' before that, then you most likely have a bad booster.
I personally lost an engine to a booster that worked like this, shatterred a piston from a major lean condition in one cylinder.