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Adding a power brake booster.

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3 years 10 months ago #210215 by Dave_64
Hi All.
Unsure if I had asked this question before, but here goes.
Assembling just what stuff I have here and what's still needed, for the 1963 Karrier Bantam rebuild.
Original brakes were a Girling type SINGLE circuit master cylinder which didn't have a booster.
I got hold of a DUAL circuit new master off a 1975 Chev C30 which has the same one and a quarter inch bore, length of stroke close enough to be the same, made up a half inch thick adapter which bolts to the original bracket, then the dual circuit bolts to it. Needs a hatch in the floor once cab sorted out for filling. The Chevy set up was for a disc front/drum rear, so wouldn't have the residual pressure valve in the front section, but after market add ons are readily available, if you know what PSI is required.

The larger Karrier Gamecocks run the same size brakes, shoes, cylinders etc but also runs a remote mounted vacuum tank, hard up against the chassis in front of the drive axle.
Like a lot of this stuff, some of it is getting hard to get. Have seen and heard quite often of people adding a small vacuum tank, quite often off a Japper of some type. Diesel engine going to be used has it's own vacuum pump.
Any thoughts?
Dave

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3 years 10 months ago #210218 by JOHN.K.
You do need a tank in case the engine stalls and you need to stop several times ..........boosters like the PBR VH90 have a fair size vacuum res built in ,and can go for several applications after the engine stops ,or vac supply is cut .
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3 years 10 months ago #210220 by Lang
Replied by Lang on topic Adding a power brake booster.
No eBay APP ID and/or Cert ID defined in Kunena configurationDave

I have put these kits on at least 5 of my old military vehicles in the last few years.

Only take an hour or so to fit. They just go in line to boost the existing system so no worry about master cylinders or messing with pedals and linkages.

The difference is hard to believe. My Dodge weapon Carrier stops as easily and well as my Nissan Patrol ute.

If by some remote chance they fail you are just back to your original pedal pressure and can soldier on'


Lang

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3 years 10 months ago #210221 by Dave_64
Lang, get your drift, but I'm also surmising that the vehicles mentioned were running a single circuit system. I wanted to go to a dual circuit system for the added safety, The way my existing pedal and master cylinder are set up, they are hard up against the chassis rail, which doesn't allow room for any sort of combo booster/ master cylinder. Have seen set ups where the master cylinder feeds the remote mounted boosters which are sometimes placed further down the chassis where theres more room. Reckon maybe Bedford or D series Ford had something like that. Have also seen setups where had two boosters set up, each one serving a seperate circuit, don't think I should have to go to that extreme. I was thinking more of simply replacing the original single circuit Girling M/C with the Chevvy dual cicuit one, and plumbimg both lines into some sort of remote booster, but as I said, most systems I have seen only allow for ONE input/output line, hence two individual boosters. Maybe not making myself clear. Already have the dual circuit M/C in place, not plumbed as yet and thus no booster as yet.Dave

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3 years 10 months ago #210227 by charlie chapman
In which part of the brake "circuit" would you insert the booster. My truck is an Austin K2, with a separate circuit for the front pair of brakes, and another separate circuit for the rear brakes

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3 years 10 months ago #210228 by Lang
Replied by Lang on topic Adding a power brake booster.
Dave

On my last restoration, the 1941 half ton Dodge I fitted an inline booster kit that had dual circuit. It split the main line from the master cylinder into front and rear. I know it is only halfway to a full dual circuit master cylinder but it has the most likely problems of blown hose or wheel cylinder covered.

I have been looking and will continue to do so but at this stage can't remember the details other than I got it off ebay (probably from China). it came with everything, hoses clips brackets etc. Standby.

Lang
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3 years 10 months ago - 3 years 10 months ago #210229 by Dave_64
Not too sure, thats why I threw it up here. Just spoke to a bloke who looked after a few D series Fords, said its not quite as simple as I made it out to be. You have to take into consideration things like the length of the piston stroke which also controls the proportioning valving. According to this bloke, said I may be better getting the original single circuit master cylinder resleeved with a stainless bore and the look for a remotely mounted booster canister, similar to the Ford type. May be the way to go, as per Langs idea. As long as the vacuum canister tank can be mounted somewhere on the chassis remotely.
Last edit: 3 years 10 months ago by Dave_64.

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3 years 10 months ago #210230 by Lang
Replied by Lang on topic Adding a power brake booster.
Dave

Don't know why you need a vacuum canister tank with a VH type in-line booster. No normal vehicle has one (and yours is just a tiddler not towing a semi). If you lose vacuum for some reason you are better off than a modern inbuilt system which relies upon it and brakes become super hard to push. You just revert to the pressure the factory designed.

Lang
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3 years 10 months ago #210232 by Dave_64
Lang,
Looks like I am not explaining myself clearly.
If I look up any of thoseVH tpe boosters, as in mod 44 or 90, whatever, it shows them as being a combination booster AND master cylinder.
Because of space restrictions.I simply don't have the room on the chassis to fit that type of combo where the original would sit.
For the same reason, cannot mount the larger Gamecock type booster/M.C.
I may not be making myself clear, so will start again. If I revert to the original single circuit master cylinder, it only has ONE outlet.
That line goes to a junction which splits into TWO lines. one going to the front brakes, other going to the rear.
So far so good. Mine never had any type of vacuum booster on it at all. AS mentioned before, next model up in size (Gamecock) had a vacuum booster built into the master cylinder but were placed in a different position, so can't use one of them either, even if I could get one.
So, unless those PBR type have a dual circuit outlet, how are they mounted?
I can vaguely recall having a VC Valiant (drum brakes all around) had the master cylinder bolted to the firewall, then had a single line going to the booster. Vacuum line was tapped straight into the inlet manifold.
Line coming OUT of the "device" bolted to the vacuum canister, ( mounted on the inside of the mudguard) went to the original brake line junction box, if thats what you call it.
I may be confusing say a "VH44" type vacuum brake set up as being the same as say a HZ Holden, where the Booster itself is bolted to the firewall, then the master cylinder (dual circuit) is bolted to it. Simple.
So, going by your last post, and referring back to your mention of the Dodge where you said you mounted one, I take it that you used the existing Dodge master cylinder (which would have been a single circuit type??) mounted the booster somewhere under the bonnet and plumbed a vacuum line into the inlet manifold. Then ran either a SINGLE or Dual line from the vacuum booster to the wheel cylinders??
As I also said, my engine already has the vacuum pump fitted to it, so would also want to utilise it If i can.
Whilst I have the cabin off, now is the time to sort out the braking.
Hope you can follow that.
Dave

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3 years 10 months ago #210234 by Dave_64
If I understand it correctly, with the firewall mounted vacuum booster with the rod going from the pedal, through the booster which the diaphragm gives extra pressure , (or at least makes the effort required less) then into the bore of the master cylinder.
Straight forward.
So, how does the remote mounted type ADD more "leverage" or add extra pressure to the brake circuit? Doesn't have any piston in it that I can see, or if it does have an internal one (piston) must be quite small.
I don't want this thing to stop on a "dime", but a few people who have these old jiggers say that the picks were never the best devised, and any small edge has to be a benefit.

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