1966 Fury , Disc Brake Booster
- Thread starter cdnfury
- Start date
Use the 68-71 bendix double diaphragm unit. The '72 and later boosters are too big around to fit the space available. If you had manual brakes to start with, you will need a power brake pedal as well. I am assuming this is for the '66 shown in your avatar
Dave
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There is more to this conversion than just changing the booster and front spindles. You will also need a disc brake portioning valve. It is highly recommended that the system be converted to a '68-'71 dual path master cylinder as well. You will need to check the size of the front brake tubing, it should be 3/16'' any smaller than that, it will need to be upgraded. Depending on the size of your rear brake shoes, it is also likely that you will need an adjustable portioning valve to re-balance the braking system. The front brake hoses will also need to be replaced as calipers use a different hose. You will need to buy or fabricate new tubing from the master cylinder to the portioning valve.
www.inlinetube.com can supply the brake tubing and portioning valve.
Dave
I'll admit that I haven't been involved with such a conversion, just looked around at parts differences in other possible brake upgrades, over the years. As the factory proportioning valve, although I haven't verified this in Chry parts, might well be the same for all models (at least sedans) and the basic f/r weight distribution was usually about 55/45 f/r, then getting the prop valve from the donor vehicle might work decently well. I also don't think the valve varied with the different rear brake shoe widths, either. In my years in GM parts, I haven't seen those things being mentioned in the GM parts books, either. That doesn't mean they are "all the same" among Chrysler products, either. There can be differences in how the lines attach, the brackets involved, and the line sizes. Getting something that pretty much fits your vehicle architecture will be the best and still be adequate for the future demands of the upgraded system.
When I looked into the sections of the 2018 Mopar Performance catalog, there was still an adjustable prop valve listed. Ford and GM also used to sell them, but I strongly suspect they were pretty much all the same, all things considered. BUT it will need to be correctly adjusted! I believe this is usually done "trial an error" and will need access to a stretch of diserted roadway or a race track to do your test/adjust on. There might be some designated starting points in the instructions, though, which could help.
IF your donor vehicle is in a salvage yard, best to "get dibs" on the brake system from the firewall forward until you've got your car back on the ground and working again! Lest another customer need something you do, get it, and then you're searching for it/them other places on other cars (which might have some differences in them, however small or large).
CBODY67
When I looked into the sections of the 2018 Mopar Performance catalog, there was still an adjustable prop valve listed. Ford and GM also used to sell them, but I strongly suspect they were pretty much all the same, all things considered. BUT it will need to be correctly adjusted! I believe this is usually done "trial an error" and will need access to a stretch of diserted roadway or a race track to do your test/adjust on. There might be some designated starting points in the instructions, though, which could help.
IF your donor vehicle is in a salvage yard, best to "get dibs" on the brake system from the firewall forward until you've got your car back on the ground and working again! Lest another customer need something you do, get it, and then you're searching for it/them other places on other cars (which might have some differences in them, however small or large).
CBODY67
The factory valves were mated to the application, ie A-B-C bodies and the various rear shoe widths. The '66 in this example did not have a portioning valve as it is a single pot master cylinder, it just had a distribution block. The portioning valves became necessary as the front discs take about three times the pressure to operate as the drum wheel cylinders. The different sized rear brakes will generally operate at the same overall pressure to the wheel cylinders if no modifications are made as part of the conversion. The problem comes with varied rear shoe width providing different stopping power, so the portioning valve needs to be mated to the size of the rear brakes for the braking to be balanced properly. The factory mated components have the balance built in, when doing a conversion using dissimilar components, an after market adjustable portioning valve is often necessary to re-balance the system. In factory applications, the balancing could also be accomplished with different master cylinders, rather than different portioning valves.
Dave
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We know that a drum brake vehicle didn't need a proportioning valve. Pressure differentials needed for the f/r balance was in the diameter of the wheel cylinders and tubing relationships. The "hydraulic leverage" of sorts.
Even then, as the brake shoes and drums got wider, the same balance would work as the shoe widths went to heavier or more "HD" use applications where additional stopping performance was desired.
The other issue is that many people, when they hear a tire skidding, might back off the pedal pressure enough to silence it. OR, quite the opposite, just put more pressure on the pedal ("for all it's worth"), relying upon the tire/road friction interface to make things happen as best it can.
Engineering issues aside, on the assembly line, if the prop valves were indeed "multiple", using color daubs to differentiate them to the vehicles they were needed on, then "assembly error" might result in a vehicle that was dangerous to stop, either from not enough brake pressure to the rear or too much. These errors would need to be minimized, whenever possible. So my suspicion is that a "will work, generally" prop valve was used rather than many specific ones, with front disc brakes/rear drums. Many road tests of the middle '60s showed a Chrysler full-size car stopping with the rh rr tire skidding (and juddering) in the magazine's panic stop testing. Some notations were that such was "normal" for Chrysler products, back then.
The key thing about brake system design is to have plenty of reserve stopping power for one panic stop, good heat durability for uneven terrain, and not too much that soft road stopping is tricky.
CBODY67
Even then, as the brake shoes and drums got wider, the same balance would work as the shoe widths went to heavier or more "HD" use applications where additional stopping performance was desired.
The other issue is that many people, when they hear a tire skidding, might back off the pedal pressure enough to silence it. OR, quite the opposite, just put more pressure on the pedal ("for all it's worth"), relying upon the tire/road friction interface to make things happen as best it can.
Engineering issues aside, on the assembly line, if the prop valves were indeed "multiple", using color daubs to differentiate them to the vehicles they were needed on, then "assembly error" might result in a vehicle that was dangerous to stop, either from not enough brake pressure to the rear or too much. These errors would need to be minimized, whenever possible. So my suspicion is that a "will work, generally" prop valve was used rather than many specific ones, with front disc brakes/rear drums. Many road tests of the middle '60s showed a Chrysler full-size car stopping with the rh rr tire skidding (and juddering) in the magazine's panic stop testing. Some notations were that such was "normal" for Chrysler products, back then.
The key thing about brake system design is to have plenty of reserve stopping power for one panic stop, good heat durability for uneven terrain, and not too much that soft road stopping is tricky.
CBODY67
Just checked the '70-'71 Chrysler parts book, only "body platforms" had different prop valves. All C-body valves (except possibly for "Y") were the same valve in a given model year. No mention of rear brake sizes, FWIW. 5-107-_.
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There is a brake warning valve and a metering valve on the '70 models, no prop valve. The prop valves came later. In any case, he is probably going to need and adjustable prop valve given the dissimilar components.
Dave
In both the '67 and '70-'71 listings, I was looking for disc-brake specific parts. Found none in the '67 listings, but did in the '70-'71 listings. Different parts groups for the "tee" and what was on the later models, too. So, with no formal "proportioning valve", how were the front/rear pressure biases for disc/drum systems done? Just curious. I'll admit I'm not that well versed in how Chrysler did these things, so I'm curious. I know what GM did with a "combination valve" (prop valve w/switch) and figured Chrysler and Ford did similar. So, just asking the question. In the mean time, I'll do some more looking in the parts and service manuals.
CBODY67
CBODY67
bulldogchesty
Senior Member
The proportioning valve is KH 89410. I am trying to rebuild one now.
The early Mopar's with disc brakes used a brass metering valve mounted on the frame rail at the spit for the left/right front brake tubing. This metering system has a small orifice inside that measures the fluid flow to keep the front brakes from applying too quickly or too slowly. Must have been an interesting design problem for the folks working on fluid dynamics! This coupled with an appropriately sized front/rear piston assembly in the master cylinder is how they proportioned the brakes.
Dave
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