Taming the HydroBeast

Seems everyone comments about how sensitive a Hydroboost is. What if you lower the hydraulic pressure, will that reduce sensitivity? Someone alluded to their being a spring in the Saginaw Power Pump that can be trimmed to lower pressure. I'd be concerned that this might lower pressure so that the power steering might be adversely effected........So

Could a pressure regulator be inserted in the high pressure line going to the Hydroboost to reduce it's pressure? Would the pressure regulator allow enough flow so that the hydroboost still worked effectively.

Anyone know what the Saginaw pump output pressure is regulated at?

Thanks

Don't have that answer - but I was thinking maybe a slightly smaller bore Master Cylinder? Might move some of the "overly sensitive" aspects.
Will be watching for other posts here!

phantomjock said:

Don't have that answer - but I was thinking maybe a slightly smaller bore Master Cylinder? Might move some of the "overly sensitive" aspects.
Will be watching for other posts here!

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I thought of that also when buying my hydroboost/MC combo. The manual MC has a 1 inch bore and the PS MC has a 1 1/8 inch bore. Seems like so many people have been annoyed with the hydroboost sensitivity, someone probably has tried a manual MC.

Anyhow just to be safe I bought a hydroboost that adapted to the vacuum boost firewall mount and a power brake MC.

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:

Are you guys installing hydro boosters out of diesel half tons? .... if so are you aware that the hydroboosters are tuned to the weight of the vehicles they are in ... That is probably why you are having trouble with touchy brakes ... and you are looking for trouble if you do this ... i have broken calipers in emergency stops ... not good. If you get a hydrobooster out of a mid 90's astro van which has similar wieght to our vettes ... you will have brakes that work perfect ... mine do.

Mr.Kiss said:

Are you guys installing hydro boosters out of diesel half tons? .... if so are you aware that the hydroboosters are tuned to the weight of the vehicles they are in ... That is probably why you are having trouble with touchy brakes ... and you are looking for trouble if you do this ... i have broken calipers in emergency stops ... not good. If you get a hydrobooster out of a mid 90's astro van which has similar wieght to our vettes ... you will have brakes that work perfect ... mine do.

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Do you by chance have any info/breakdown on these HB units??

all I can find is a bunch of part numbers and NO breakdown pix with any reference .....

I just installed a ebay HB unit on a P30 camper project, and have NO assist at all from it, the output end of the unit does not look like the one on the vette at all....I think there are some missing parts....the pedal is hard as a rock, almost no give at all, but it does act like manual brakes, in other words, extremely hard to stop the thing....

:friends:

No ... I have no info on them ... I have just played with them abit ... there used to be a company called hydratech that did hydro boost conversion kits ... the owner used to be extremely knowledgeable on them and would tell you anything you wanted to know, but the last time i called him, the companies name had changed and he was not answering phones ... I doubt you are missing any parts ... not much can be taken off of them without them leaking fluid like crazy .. i suspect that it has a bad seal inside .. but i have never ventured inside of them ... just replaced them when they quit working ... sorry i can not offer much help ... but if you are building a camper vehicle .. just head down to the local truck junk yard and grab anouther off of a 3/4 or 1 ton truck ... should be lots of those around and not to pricey

Going to Rock Auto for instance, I find the say '85 chebby P30 motor home chassis had a few engine options from diesels to BBC....

and so the pumps varies a bit in part numbers...

not sure what is going on there....

is it the pump itself or the housing with two return ports....I just T'd the lines on the vette, works fine...

did the same on the Clamper/Motor home....

IF I get engine speed up, I can get the power steering back, but to test brakes at say 2000 rpm engine....I have to be careful as it's in a hilly driveway...

so I hesitate to mess with it a whole lot that way...

what I really want is to change the output valve, and see what happens...as I dunno what that junkyard pump had on it....

like I said, the vette had all the same stuff and when I added the HB, no problem, just motored right along...

:surrender:

when you say Ted the lines ... do you mean the return lines to the pump? If you lost power steering after you put on the hydro boost ... i would suspect that the hydro boost is by-passing all the preasure in the power steering system out the return of the hydro booster ... this is a sign of damaged seals inside the booster ... alot of failures happen to the hydroboosters, when the PS pump fails and puts shrapnel through the PS system ... the shrapnel scores the cylinders in the booster and you get all kind of wierd problems ... had one that would apply maximum preasure to the brakes as soon as the engine would start ... we tried to find parts one time for rebuilding the hydro boost units but had no luck here in canada ... and now a days the junk yards are full of them for $50 bucks a pop so it is not even worth our time to try to fix them ... just put on anouther ... good luck in your fight but i would bet you got a damaged booster.

IF you can find one, HB units are over 100 bux here....in Florida....

never even seen one at either of two junkyards....

I call around and all I get is negatives....

:flash::sweat:

well negatives are no good .... and it will cost a 100 bucks if i try to send some down to you ... and i can not promiss that the wrecker ones will be good and if you have to send one back then that just costs more money. if you get a bad one from a wrecker here they just keep swaping them untill you get a good one. Sorry i can not be much help....

Mr.Kiss said:

well negatives are no good .... and it will cost a 100 bucks if i try to send some down to you ... and i can not promiss that the wrecker ones will be good and if you have to send one back then that just costs more money. if you get a bad one from a wrecker here they just keep swaping them untill you get a good one. Sorry i can not be much help....

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No sweat man, I think I can figger it out, and I suspect it's not the booster, but pump flow/pressure and so to figger out how to change that....

then the issue is that I have the largest m/cyl there is on this truck, wonder if maybe somehow it's too much?? can't see that with ~1000 psi on the pump pressure, supposedly....

:shocking: