I started a new thread so we can do some brainstorming on power brake boosters.
I am not happy with the amount of boost I get from the OEM booster. 50% more would be nice.
My biggest reason is my right knee. I have been driving Ol' Red 30 years, now. Because of my long legs, I have to hit the brakes with my right leg angled. This is wearing on my knee. I want to reduce the pedal effort to something a bit closer to my son's Accord Coupe.
Jim Stabe has just upgraded his ride with two new remote boosters.
http://forum.britishv8.org/read.php?7,64513,64528#msg-64528
So what will it take? Two remote boosters, like Jim? Or, maybe find a dual booster that will bolt to my master cylinder?
Does anyone know the ratio of the OEM booster?
Gonna spend some time investigating a 7" dual diaphragm booster.
I think stock is a 6" single. The 7" passes the eyeball test. As a friend once said, " That's do-able." Great positive attitude.
How much more boost? Don't know, yet.
How about a link to that booster Jim Staube used? I'd like to give it another look.
Jim
Carl,
Here is my dual 7" Booster. Been using it for about 17 years and it's worked great. Finish is showing it age but other than that no complaints. Bolted straight to stock location on my 1980 B. Got it from a hot rod parts web based company in WA. Ford 7/8" master, maybe, don't recall and I am a poor accountant etc. Great pedal effort, more power than stock but it did not lose any feel. Bit tight with my FI but just cleared air intake as you can see.
874CDBF1-06A9-4B01-B96A-33F236596EF6.jpeg
6DE263E7-C7ED-4A58-A737-8DF2C35467FA.jpeg
And here I thought I had stumbled across a new, easy brake mod!
Did you have to extend your brake lines, Mike? How much did it change the pedal effort?
Jim Stabe said he used two VH 44 remote boosters by PBR. They are available in different specs.
From Jim:
QuoteGoogle images had a few spec sheets for different versions of the VH44 and also for the larger VH40. The specs included the output port size and the ones I got had a 3/8" 24 thread in them. I connected to my existing plumbing by using a 3/8 24 to -3 AN adaptor with a copper washer and then using 37 degree -3 AN tubing nuts and sleeves. Some of the versions used 5/16 output threads.
(http://i3.photobucket.com/albums/y83/dattoman/Brake-Parts/vh.jpg)
http://hydroboost.com.au/boostertypes.htm
http://hydroboost.com.au/techtalk.htm
Carl,
Needed 3 short section of lines. Other than that it's stock lines but with addition of 10lb residual valves on rear and a rear bias valve. Car has Rover SD1 4 piston calipers though, so tough to give direct comparison to stock booster as it was all done at same time.
597CFBB3-4597-40A5-8DF9-DFDB70DBDF71.jpeg
0EF9BBBD-6DF4-47AF-AC61-5D2E1787E319.jpeg
Thanks Mike!
I have been planing to add a 2 lb residual valve to the front. So adding a 10 lb to the rear would take car of needing slightly longer brake lines. Since, I think, the 7" dual booster is longer than the OEM booster.
There ya go, Graham. Git'er built & let us know what ya think. ;)
Hmm, another angle. Is it possible to get a same size as OEM booster with a higher boost ratio?
I'm far from an expert on boosters but I believe that dual diaphragm units have a greater pressure rise than single diaphragm units. Not sure what a stock MGB comes with but it might be worth a couple phone calls to the folks that make them.
One issue that I'm reading about is that boosters require a minimum 17-20" vacuum to operate correctly. One typical 7" dia., universal booster advertised on ebay, specifically notes that "requires 18" vacuum".
Given that my cam gives me, at best, 13" vacuum at idle, I'm not convinced that a booster is available for my setup.
Guess I stick with manual brakes unless someone says otherwise!
Graham, Muscle car guys use a vacuum reservoir(can) to compensate for low idle vacuum.
https://www.youtube.com/watch?v=v9G0TN4ZacM
Analysing what you posted, Jim, it seems to me that addition of a reservoir only adds reserve volume to a system without addressing the fundamental issue of low vacuum. After all, isn't brake/booster performance increased when there is a larger pressure delta across the diaphragm.
Doesn't it makes sense that if atmospheric is on one side of the diaphragm and 13"Hg vs 20"Hg on t'other side, that pedal assist would be noticeably different.......or am I overthinking this!
Maybe that's why Carl's brake performance is questionable....not sufficient vacuum!
Graham, this video explains it pretty good:
https://www.youtube.com/watch?v=0OMIzCvYefY
If you look at what you are doing when braking, you may find you have more than enough vacuum. At idle you may only have 13" but when you are traveling at 40, 50 60 mph you are more likely at 16" or better. Suddenly you need to stop, you lift off the gas and apply the brake. While you are driving along at speed your vacuum is likely 15"-17" but when you take your foot off the gas the vacuum jumps to 20" or more. and with a reservoir that has a one way check valve, the vacuum will be captured at the higher level. My car idles at 16" and cruises at 15" to 17" but when I let off the gas it is way over 20" and the booster works very well. You seldom need boosted brakes at idle.
Gents - thanks for the enlightenment!
Carl
A few newer GM cars use an electric vacuum pump. I know that the Chevy Cruze does for sure and it is there to add supplemental vacuum for the brake booster, due to the small engine displacement and the fact that it's turbocharged.
I seem to remember seeing them on newer Tahoes as well. Not sure what year though, but I'm thinking in the 2010 to 2013 range. 2015 and newer use a mechanical vacuum pump that is belt driven.
I would think that it may be possible to incorporate the electric vacuum pump in the system with a vacuum switch that turns the unit on if the vacuum drops to a certain level. The best part is that they are fairly small and could be mounted just about anywhere.
With higher vacuum applied to the booster, you may even find that the stock booster is adequate!
Bill
Thanks, Bill!
I have been aware of using a reserve vacuum can for a long time, as I have huge cam in my Camaro. Never occurred to me that I would need one for my MGB. I guess first order of business is to measure it. The high comp. JN block does use a slightly larger cam.
I noticed that the remote boosters have different ratios, so thought maybe I could find a direct swap that had a higher ratio. They don't always give that info, though.
I ran across this on the internet this morning. http://brakepower.com/help_abc_16_BAR_t.htm
The booster itself is a vacuum canister, and should hold enough for one or two boosted applications, maybe more depending on how hard you hit the pedal. An aux canister will add more uses between. You can base the size on the booster itself.
Jim
Yeah, a reserve canister is not going to help an engine with low vacuum to begin with. I guess that means using an electric vacuum pump, like Bill suggested.
Here is a Brake Bias calculator to go with the one Jim S. posted.
http://www.tceperformanceproducts.com/bias-calculator/
This is the calculator I used to design my brake system. It is an Excel spreadsheet so I couldn't post mine on this site but you can download it - it is the attachment in the first post. I like this one because it takes center of gravity height into account as weight is transferred during a stop. It came out pretty much on the money for my car.
http://locostusa.com/forums/viewtopic.php?f=5&t=14424&p=153058
My TR6 with its big cam, made 7" at idle. And it does matter, because if you're tootling down the high street at pretty much idle, that's how much vacuum you have when some pedestrian walks out in front of you.
So I fitted an electric vac pump and a vacuum switch, gave me 19".
Worked well for the five years I ran the car.
Ivor
Thanks for the link on that spreadsheet. After inputting values it is obvious from the results that I have a problem in the front calipers. Must be some stuck pistons, blockages, or something. Didn't think it was working the way it should.
Jim
Finally went out & measured the vacuum on my engine. Warmed up, it pulls 17" with an occasional dip to 16". When I reve the engine to 2500rpm or so & let off, it jumps to 21". That seems pretty normal at my altitude of 1450'.
The MGC, over the years, had a number of different booster ratios available ranging from 1.6 to 3.0. Rather than changing my booster to something else, I would like to source a stock size booster with a higher boost ratio. If, there is such a thing.
Hmm....
QuoteIMHO the PBR VH40 units, either in dual NA spec or solo EU, AU configuration, are state of the art direct replacements for the OEM calibration of the Girling MKIIB units. I have only spent a little time going through some barely legible spec information to conclude the VH40 PBRs have about a 30% more effective boost than the OEM Girlings which compare nearly equally to the larger Lockheed substitutes. -Robert Kirk
https://www.mgexp.com/forum/mgc-forum.48/new-brake-boosters-again.2096630/
Nevermind, the PBR VH40 boosters are remote only.
Carl, I saw a picture recently of a dual diaphram street rod booster in a MGB but can't find it now.
On this thread, Jim? ;)
Mike Stemp posted some pics of his on page one. Seems the way to go.
Carl, Yep, that is the one. I looked everywhere except page one on this thread. Speedway has them:
https://www.speedwaymotors.com/Speedway-Dual-Diaphragm-Power-Brake-Booster-7-Inch-Chromate-Finish,8446.html?sku=91031432&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=EAIaIQobChMIgeeQneXJ4QIV7h-tBh2dyweGEAQYAyABEgLEkPD_BwE
Helpful video on that link too. Not too long.
So to be clear, the advantage of the dual diaphragm is that it doubles the pressure applied to the M/C? (for the same booster diameter)
Jim
I don't think it doubles, Jim. Just eyeballing the 7" dual booster, the front diaphragm looks to be a good bit smaller than the rear.
Not much info out there on actual booster ratios. Did find this on Ebay:
"A 7" Dual booster gives you 27% more stopping power than a 7" single"
I think the MGB booster is a 6", so a 7" dual booster should be quite an improvement.
Well, I'll tell ylou something about boosters you probably already know; they can leak.
The Bendix Hydro Vac on my Rambler had 56 years in service, it was working, but I thought it was time for a refresh, so I sent it for rebuild.
On return, they mentioned that it had a big vacuum leak and on their test rig it didn't work at all.
Now, their test rig doesn't have a 327 vacuum pump, so it was working on my car.
And even with the engine off, it held some vacuum.
But as I now realise, it wasn't working very well. The brakes now are a lot sharper.
And, I've had an intermittent problerm where the engine won't idle. Happened after a long run when it was thoroughly hot. Couldn't find any cause, thought it was bad petrol.
And. it used to pink on acceleration even though the timing is correct,.
Now, both those problems have gone.
Cause? I guess, the vacuum leak.
The more stuff you have, the more there is to go wrong.
Ivor
I bought the dual diaphragm booster from Speedway referenced earlier in this thread and installed it along with a new master cylinder (the master cylinder was needed because the stud spacing is much wider than the MGB master cylinder hole spacing). The boost is much more effective than stock, pedal effort is far lower but the brake feel is still very progressive.
The booster fits the MGB location without modifying the mounting surface. However, for ease of installation (relative), I shortened the mounting studs on the booster so that the retaining nuts could be tightened with a ½ inch socket on a 1/4 inch wobble drive extension. I also had to make a clevis to adapt the booster input push-rod to the MGB brake pedal. The booster push-rod is threaded 3/8-24 and clevises fitting that are way too big. I made the clevis from 1/8 inch thick, ¾ inch wide bar stock. I bent it around a 3/8 inch bolt (to get the proper spacing), welded a 3/8 stop nut to the end, then drilled through the clevis and threaded it 3/8-24, starting the tap in the stop nut. To finish, I drilled the clevis for the brake pedal pin, then compressed the ends in a vise so that the cotter pin would go in the end of the pedal pin. I also shortened the booster push rod as needed. The master cylinder fits on the booster with no clearance problems with the hood. Plumbing was simple because I have 4 wheel disk brakes and had no need for proportioning valves or pressure retention valves. But there are many master cylinder options besides the Wilwood cylinder I used. Just about any GM, Ford, or Chrysler cylinder will bolt up to the booster and these are available for disk/drum configurations with built-in pressure retention valves for the drum circuit. I do not know if these alternative master cylinders will fit in terms of hood clearance, but for reference the Wilwood cylinder I used is 8.15 inches long, 3.22 inches high from the center of the bore, and 3.14 inches wide at the reservoir. The widest part of the reservoir is about an inch from the side of the engine compartment and the height of the front of the reservoir is about equal to the top of the channel containing the fender bolts. Note: the Wilwood master cylinder came with a push rod extension that goes between the booster and master cylinder. This may be needed but not included with a different master cylinder, but the extension rod is available separately from Wilwood.
booster.jpg
clevis.jpg
Damn you, Larry.....now you've got my project wheels turning.
...nice installation summary.
Pretty clean install Larry, worth keeping in mind.
Jim
Is that 7" diameter booster, Larry?
It is a 7 inch booster;
https://www.speedwaymotors.com/Speedway-Dual-Diaphragm-Power-Brake-Booster-7-Inch-Chromate-Finish,8446.html?sku=91031432&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=EAIaIQobChMIgeeQneXJ4QIV7h-tBh2dyweGEAQYAyABEgLEkPD_BwE
Thanks, Larry. Please post your review of the swap. This is something I have pondered for quite some time.
Larry, What is the piston diameter of your Wilwood master cylinder? Thanks.
The piston diameter is 1 inch. This is also rather commonly found in OEM master cylinders.
I have now driven a few hundred miles with the new booster and I can report that it works even better than I expected. It allows the true power of the Wilwood front brake conversion to be realized. Pedal effort is low, very much like any modern car, but the brakes are easy to modulate. The highest speed stop I have tried was from 90 mph and it was effortless. This is almost a bolt in conversion with only minor fabrication needed, and probably has the biggest improvement vs time or cost of anything that can be done to an MGB. I am hoping someone who already has the stock MGB booster tries this and provides an independent assessment of the advantages...
Thanks for the update, Larry!
I plan to, maybe this Fall. Do you think it would provide similar results with the OEM master cylinder size?
With a smaller bore master cylinder the booster will appear to be even more powerful but there would be a somewhat longer pedal travel than what I have. However, if you have stock brakes pedal travel will be stock, but I assume you have upgraded brakes...
In any case, you will need a new master cylinder since the MGB cylinder flange is too narrow.
I have always had stock brakes. Still have the original front rotors on the car. :)
I guess you don't get them turned when you replace the pads?
I may have had them turned once in 1991. I need to measure them again. I'm sure they are at or below minimum specs by now.