All I can do is relate MY experiences over time with regard to GM braking systems....
number ONE, as to my final observation...vacuum sux....
so how did I reach that conclusion??
after driving GM cars of various sizes for some decades, along with imports and Ford/Chrysler over the similar time frames....I found I got used to the universally squishey feel to brake pedals...but then again, i'm 6'5" and have a size 13 WWW foot....so if I hit a brake, that silly bitch better be solid and 4"+ of travel to the floor just never really GOT it far as I"m concerned....
so that is history....now to my '72 shark...and MY observations...which lead to the sequence of mods/build over some years...call it almost a decades' worth...
daily driver, every damn day I can find a excuse....this is NO garage queen...
I am not Rocket J. Super Squirrel, but I dont drive slo either...typical for most guys...
the car was dead stock when purchased in '95....I put serpentine drive and some electric fan mods on almost right away...the rad/pump having failed, and me having the parts in the garage...so I put that before the FI install...
one of the things was the 'new' serpentine pump had this O ring output pipe and so not knowing jack diddly about pressures...I stuck the stock '72 valving in the '88 pump ....thereby reducing the pressure from ~1500 psi to nearer 900 psi.....per my recollection from Jim Shea....
stock power steering ran fine, for some 5+ years....but the brakes were a bit less than most GM cars...I wrote it off as 4 wheel disc and so let it go...pedal feel being less than other GM cars of the era...never ANY of them all that great...too much travel, then the squishy feel at the bottom...but in a emergency they did stop the car ok...so fuck it...leave it alone...
so skipping the steering rack install which did not affect the brakes one bit, but handles well.....I was reading about this Hydro Boost...and after doing the larger diameter TRUCK master cylinder, I finally decided to do the switch...
and the car stopped like KRAZZZZY mad with that truck m/cyl on there, never having broken a hydraulic line on the HB install....
it was SO sensitive I went to a stock piston diameter m/cyl....to lessen the shorter travel of the brake pedal....
that is the final configuration....
upon tearing out the brake booster, I found #1..the thing held vacuum just fine with engine off....
there was a spring between the pedal rod and the m/cyl actuator rod...look at the GM overhaul manual for vettes..i'ts shown...it's a tough spring, but about 1" diameter and about 1/2"? of give to it....
well, 1/2 inch at the booster is about 6' at the pedal....
:hissyfit::hissyfit::hunter: