Brake master cylinder compatibility - Vintage Mustang Forums
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post #1 of 5 (permalink) Old 07-11-2019, 07:42 PM Thread Starter
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Brake master cylinder compatibility

Hi Friends

So I think I have the theory in my head correct. If I buy the enclosed link master cylinder. I would not be able to hook it up with a 4 drum brake vehicle without adding a 2 inch long inline residual valve and perhaps the valve in the master.

Which means if I want to convert to a front disc upgrade kit at some future point I need to modify brake lines again.


https://www.ebay.com/itm/M-B-M-1964-...M/222793539422



https://www.ebay.com/itm/1964-5-1973...item25dd15c1d6


Ideas ?


Thanks !

66 Fastback

289 Auto C4 "C" code with added 4 bbl


We've got a full tank of gas, half a pack of cigarettes, it's dark... and we're wearing sunglasses.
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post #2 of 5 (permalink) Old 07-12-2019, 12:38 AM
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Originally Posted by malstrom View Post
Hi Friends

So I think I have the theory in my head correct. If I buy the enclosed link master cylinder. I would not be able to hook it up with a 4 drum brake vehicle without adding a 2 inch long inline residual valve and perhaps the valve in the master.

Which means if I want to convert to a front disc upgrade kit at some future point I need to modify brake lines again.


https://www.ebay.com/itm/M-B-M-1964-...M/222793539422



https://www.ebay.com/itm/1964-5-1973...item25dd15c1d6


Ideas ?


Thanks !

Residual pressure valves are recommended, but the number of drum to disk conversions that omit them, without even realizing, is somewhat staggering. You would want a residual pressure valve and you'd probably want one inline to both front and rear circuits if using a non-drum master (this one appears to be disk / drum - so make sure there is no residual valve in the rear circuit already from the master cylinder). All drum / drum systems I'm aware of used residual valves @ 10PSI +/- to both circuits, but I'm not a "Mustang expert" so, take that for what its worth. You would NOT want to retain the combination valve however (looks like a standard Pv2 unit) - It would direct and delay pressures inappropriately for a drum / drum system - that being the case, you'll need to re-plumb your brake lines anyway if you move to disks later.



A note on residual pressure valves - those suckers leak. I mean, perhaps not all of them, but I've found them to be yet another weak link. You might look into an appropriate thread sealant - its the only way I've got them to hold, you shouldn't have to technically, but such as it is.



Allan.
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post #3 of 5 (permalink) Old 07-12-2019, 01:24 AM
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You should not use that brake booster kit with drum brakes. It has a PV2 combination valve, it's the brass thing that hangs under the master cylinder. Here's a couple of links to help you understand that valve: 172-1353 AC Delco Reproduction Proportioning & Combination Valve - classicperform.com/Instructions/PDF/PVK.pdf

Maybe you can use the kit without the combination valve for 4 wheel drum brakes. Then you might need residual valves instead. Then when you decide to change to disk brakes in the future you will need to fabricate all the brake lines again...

The Pirate Jack disk brake kit should work with the booster kit.
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post #4 of 5 (permalink) Old 07-12-2019, 10:12 PM
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If you're planning to do the disc brake swap at some point but want to do the dual-circuit master cylinder upgrade NOW, but the cheapest '67 manual brake master cylinder you can find, run the front brake line to the existing distribution block and put a plug into the rear circuit port in the block, and run the rear line directly to the rear line directly to the master.

You're not going to find a practical solution to upgrading the master to one that will function properly with both 4-wheel drum and disc/drum systems. Either do the disc brake and master upgrades at the same time or spend the extra fifty bucks.

Bart

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post #5 of 5 (permalink) Old 07-13-2019, 02:36 PM Thread Starter
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If you're planning to do the disc brake swap at some point but want to do the dual-circuit master cylinder upgrade NOW, but the cheapest '67 manual brake master cylinder you can find, run the front brake line to the existing distribution block and put a plug into the rear circuit port in the block, and run the rear line directly to the rear line directly to the master.

You're not going to find a practical solution to upgrading the master to one that will function properly with both 4-wheel drum and disc/drum systems. Either do the disc brake and master upgrades at the same time or spend the extra fifty bucks.


thank you Bart, Cougar70 and Treozen

I guess I cant make a two step process out of this. Sure glad I asked before buying the master.

I would not wish to rip out and plumb brake lines twice. I am finishing the rebuild of new drum wheel cylinders a stained possibly leaky hose now. Just to get the car back one The road.


I am so mad and depressed that DOT 5 has rusted the bottom only of the master and not the sides of the bowl. WHy all this damage with wet tries in thee years of storage I dont know.

So any idea on how to clean that old single master bowl. lintless rags, brake cleaner ( maybe not) alcohol.?

66 Fastback

289 Auto C4 "C" code with added 4 bbl


We've got a full tank of gas, half a pack of cigarettes, it's dark... and we're wearing sunglasses.
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