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Decent Vacuum Booster/Master?

Shawn

Shawn

Nuckin Futz!
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Earlier this year I was gung-ho for doing a hydroboost setup but after reading about some issues with having a ram and you need to send it to a place to remove the restriction I think I might stick with a vacuum booster setup with the larger dual diaphram 11" booster and keep things simple under the hood. Has anyone had success with a GOOD vacuum booster/master setup with 4 wheel disk brakes?

I see ones like this from CPP and I know others have suggested the C30 aluminum master with a good booster.

booster.jpg
 
@skunked changed like 6 of these a year or so ago. He had a supplier that was pretty decent to work through his issues
 
I actually had good luck with my old stock 87 master/booster but being a dumbshit I sold it cheap when I thought I was going hydro. Sigh...

Since I have to put a new master in thought I'd check for any better options for better stopping like a hydro setup. A master suited for 4 wheel disk brakes should be a better fit. The only thing that worries me is the cam size might be a little on the larger side. I need to call Comp Cams and see how much vacuum they predict if that's even possible or just get my frucken engine running and measure vacuum myself.
 
Not sure where my booster came from but we put the same one on Dad’s ‘68 Chevy P/U. Neither one has brakes at idle. I’ve tried moving the vacuum hose and changing the check valve. No brakes at idle. The guy at the local speed shop said he just saw a guy change out 6 new boosters in a row before he got a good one.

Edit: The booster is gold in color if that helps.
I was being sarcastic about no brakes at idle. They’re there, just no vacuum assist.
 
My blazer has a p30 master cylinder from a later model that is disc disc. I use my stock booster.
Years ago it was talked about pretty heavy here. Dont remember the specifics.
 
Engines make the most vacuum at idle..as RPM increases,vacuum decreases..
If the booster works better past idle,I'd suspect it is not getting sufficient vacuum to the booster--I'd think if anything the booster would lack power assist beyond idle ,more than AT idle!..
Sure its hooked to manifold vacuum,and the fittings and hoses aren't restricting the vacuum supply ?..
 
Last edited:
wasted wages said:
I just put a booster and MC from Summit on my '68 2wd... It uses some kind of pivot arm that comes off the brake pedal arm between the booster and the arm.
I converted the front drums to disk at the same time. The offset bracket seems to increase the amount of brake pedal effect without causing more pedal effort.. If that makes sense...

look here:
https://www.summitracing.com/parts/sum-760197/overview/year/1968/make/chevrolet/model/c10-pickup
Click to expand...
Yes the 67-72 trucks mc/booster has this funky setup.
It doesn't make it any stronger than the newer 73-87 style though.
 
wasted wages said:
I just put a booster and MC from Summit on my '68 2wd... It uses some kind of pivot arm that comes off the brake pedal arm between the booster and the arm.
I converted the front drums to disk at the same time. The offset bracket seems to increase the amount of brake pedal effect without causing more pedal effort.. If that makes sense...

look here:
https://www.summitracing.com/parts/sum-760197/overview/year/1968/make/chevrolet/model/c10-pickup
Click to expand...

What's with the tiny booster?
 
Appreciate the comments. I wanted to stay away from the smaller boosters. I want the larger 11" boosters with dual diaphragms. The larger booster will always win for the the strongest force for brakes. And
@diesel4me is correct on the vacuum.

I did some more research on my cam and I believe it its only going to produce around 12 inches of vacuum. Thats not going to give the suggested 18 inches of vacuum required by most boosters. It will kind of work, just have a harder brake pedal.

Comp Cam Specs
Intake Duration at 050 inch Lift:230
Exhaust Duration at 050 inch Lift:236
Duration at 050 inch Lift:230 int./236 exh.
Advertised Intake Duration:280
Advertised Exhaust Duration:288
Advertised Duration:280 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.576 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.570 in.
Valve Lift with Factory Rocker Arm Ratio:0.576 int./0.570 exh.
Lobe Separation (degrees):113
Computer-Controlled Compatible:Yes
Grind Number: 280XFI HR13

The only two fixes for a larger cam is a vacuum pump ($300) or go hydroboost. So maybe its best I stay with my original plan and stick with hydroboost and have the booster modified for the ram since that will be the cheapest option.
 
This explains the mod on the hydroboost.

quote-
Well, I'll say this; the hydroboost unit requires full compatibility with all prior brake and steering upgrades/modifications!
Immediately after installing the hydroboost, I noticed four minor issues:
1) The hydroboost unit itself, is an inherent 'fluid flow restriction' that slightly reduced power to my ram-assist steering and consequently returned some 'road feel' when driving. I liked this since the ram-assist had more power than I needed anyway. I removed my steering stabilizer again and left it off.
2) My '78-'79 F350 1 1/6" master cylinder was simply too small (volume-wise) for use with hydroboost, due to the large front calipers & rear disc brakes I installed and because I prefer a shorter, firmer pedal stroke. I knew that installing the typical 1 1/8" master cylinder wouldn't make much difference, so I researched and found a '76 F350 1 1/4" master cylinder (Raybestos MC39014). This became the perfect master cylinder for my hydroboost brakes. It fit the JBG Hydratech unit (mounting stud spacing) and it firmed & shortened my pedal stroke.
3) Using synthetic transmission fluid (like I had been for years) was slightly foaming the fluid but wasn't causing any actual driveability issues. I tried Valvoline SynPower power steering fluid and it was worse; it's garbage! (Valvoline discontinued it.) I flushed and refilled with Royal Purple Max EZ power steering fluid and the issue cleared up completely. It's the best power steering fluid I've ever used.
4) Lastly, I realized the hydroboost unit was momentarily interrupting fluid flow to my ram-assist cylinder, under hard braking. I was almost expecting this since I had often heard about it. Well, I was so happy with my ram-assist steering, that I wasn't going to tolerate this problem.

After doing some research, I learned the hydroboost is designed to 'priority feed' pressure to the brakes, while simultaneously restricting pressure to the steering gear (especially under hard braking). I had two choices; either disassemble my new hydroboost unit to grind an internal passage between the pump port & the gear port (so the spool valve couldn't restrict fluid flow) or send it to Vanco for their Hi-Flow modification. Being a true "do-it-yourself" type of guy (and being 99% successful at many modifications I've done), I decided to jeopardize my hydroboost unit. It was a risk I was willing to take because if the modification didn't work, I'd have to send it to Vanco for repair anyway (and I just had to know). I had previous hydroboost rebuilding experience & good literature. So I removed the unit, disassembled it, neatly ground a passage between the two aforementioned ports (Dremel tool), cleaned and reassembled it. After the reinstallation, I went for a test drive and quickly realized that I had ruined my new hydroboost unit. The steering worked great (no interruption when braking) but the hydroboost unit lost most of its power assist. I thought my high output steering pumpwould be enough to feed both, steering & brakes equally BUT evidently, this needs to be metered/controlled by the hydroboost spool valve. So if any of you were contemplating this, don't! I then sent my hydroboost unit to Vanco for repair and their Hi-Flow modification. I received excellent customer service and Van charged me a good price. Van told me, in regard to my Hi-Flow attempt, "God bless you for trying...you were right there...but you just did the wrong thing".

When I road tested my 'Vanco repaired & modified' hydroboost unit, I was amazed at how well the brakes and steering worked together.
I noticed these three things:
1) The ram-assist cylinder's fluid flow was no longer momentarily interrupted when braking.
2) The Hi-Flow modification seemed to make the power steering fluid 'bleeding process' easier & faster.
3) The Hi-Flowed hydroboost unit was no longer a slight 'fluid flow restriction'. It increased power to my steering and I lost that small gain in 'road feel' (that I got when initially converting to hydroboost). LOL! I've been driving this "finished product" for almost four months and it's been flawless. My '78 Bronco finally has the steering & braking quality you'd expect from a new truck.
I hope my experience helps someone else.
 
Shawn said:
Appreciate the comments. I wanted to stay away from the smaller boosters. I want the larger 11" boosters with dual diaphragms. The larger booster will always win for the the strongest force for brakes. And
@diesel4me is correct on the vacuum.

I did some more research on my cam and I believe it its only going to produce around 12 inches of vacuum. Thats not going to give the suggested 18 inches of vacuum required by most boosters. It will kind of work, just have a harder brake pedal.

Comp Cam Specs
Intake Duration at 050 inch Lift:230
Exhaust Duration at 050 inch Lift:236
Duration at 050 inch Lift:230 int./236 exh.
Advertised Intake Duration:280
Advertised Exhaust Duration:288
Advertised Duration:280 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.576 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.570 in.
Valve Lift with Factory Rocker Arm Ratio:0.576 int./0.570 exh.
Lobe Separation (degrees):113
Computer-Controlled Compatible:Yes
Grind Number: 280XFI HR13

The only two fixes for a larger cam is a vacuum pump ($300) or go hydroboost. So maybe its best I stay with my original plan and stick with hydroboost and have the booster modified for the ram since that will be the cheapest option.
Click to expand...


Wasn't aware your can was swapped,must have missed that ..
For sure a hotter cam will reduce manifold vacuum,thus leading to your lack of power assist...
Some cars have factory electric or mechanical vacuum pumps,maybe you can get one off a salvage yard donor,I think some Volvo's used them ?..
I looked into getting one to replace the one on my 6.2,but got the govenor on the TH400 modified by Greg Ducato ,which has helped it shift much better ,so I backed off looking for one..
 
diesel4me said:
Wasn't aware your can was swapped,must have missed that ..
For sure a hotter cam will reduce manifold vacuum,thus leading to your lack of power assist...
Some cars have factory electric or mechanical vacuum pumps,maybe you can get one off a salvage yard donor,I think some Volvo's used them ?..
I looked into getting one to replace the one on my 6.2,but got the govenor on the TH400 modified by Greg Ducato ,which has helped it shift much better ,so I backed off looking for one..
Click to expand...

Yeah sorry, entire engine has been swapped out and went a little too hot on the cam I guess. Old 496ci with mild cam worked nicely with old stock booster. I'll see what I can find looking for volvo vacuum pumps.
 
My buddy has a vacuum pump sitting on the shelf, I'll ask him if he wants to sell it.
 
So I called Vanco to port the hydroboost booster today and price was more than I was expecting.

-To rebuild and port a good core $450
-new ported hydroboost booster $700
- new booster / master / hydraulic lines $955

Vanco master part is from 82 Vette and is the standard iron.

I may get a good core for $35 and send it but thats still lots of cash to spend on a booster only. Makes me want to just stick in a 7/8" Wilwood master only and call it a day...
 
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