The Stovebolt Site Forums The Shop Area Driveline 46 1/2 Ton Dual Master Cylinder?

Was looking to see if anyone has installed a dual circuit master cylinder on a 46 1/2 ton with drum brakes? I checked the OEM single circuit brake cylinder and it has a 1" bore diameter and a 1.5" stroke.

I tried an ACDELCO 18M1020 (recommended by one of our Canadian friends) which has a 1" bore (but a longer stroke) It does not generate enough stopping power.

If you have accomplished this I would appreciate the master cylinder model # you used.

Best regards,

Larry

I wanted a dual master cylinder for my '46, but could never find one. I wanted something that would just bolt in place. '47 and up has a conversion option for this upgrade, but I think there would be some fabrication to make it work for a '46. I'm just sticking with the stock master cylinder for now, but interested if someone has a simple solution for all-around drum brakes.

Every car I own has a single reservoir mc (Ford trucks excepted) and that's all I've ever owned. I've never had a brake failure. As much attention as antique cars get from their owners, leaks are likely going to be found long before a failure.

As a counterpoint, I suffered a catastrophic brake failure on my buick and narrowly avoided an accident because it had a dual MC and the rear brakes still worked.

There were no leaks, but one of the braided softlines blew out of its crimped end during a hard stop and I lost the front brakes.

I am a big proponent of modern braking safety equipment.

Not knocking modern advancements but catastrophic sudden failures are rare. I keep my vehicles, especially brakes, in perfect working order and check everything frequently and repair things as soon as I find a problem.

Yes I have done this conversion on my 46 1/2 ton
I used a corvette manual (not power) disc brake master (‘83-‘84) 1” bore.
Per photo I bolted a L plate to the existing support plate of the original master, which moved it back some.
I put residual pressure valves, 1 front 1 rear, and an adjustable proportioning valve on the rears.
I used a grade 8 bolt to extend the pushrod, (cut off the head and rounded/polished that end).
My truck has a T5 gearbox. Required a new hole in floor for access.

Did/does it work? Yes but Keep reading….

My truck came to me with tired huck front and good bendix rear drum brakes on a shot single master cylinder. Braking sucked.
I rebuilt the front hucks with all new slave cylinders, shoes, springs, turned drums, etc and since the master cyl was crusty inside I installed the corvette split master. Brakes still sucked (don’t mix bendix and huck…)
I got a set of bendix 54 hubs and backing plates for the front from a fellow bolter,-installed with new drums turned on the hubs, new studs, new slave cylinders, shoes, springs, roller bearings, replaced all the steel brake lines, and DOT certified SS braided/ coated flex lines.

Yes, truck stops great now, rock solid pedal, reasonable pedal pressure, and pedal travel right…. Adjusted bias so with no load it just starts to lock the rears in a panic stop test.
Its brakes, I kept at it until it was right on. Wouldnt settle for less.

Hank's, what are the red fittings on the brake lines?

I guess I should state that the brakes on my vehicles are all rebuilt to factory spec with no mixing or cobbling together of parts. Ol' Roy's Huck brakes on all 4 corners work great as they were designed (and restored).

Residual pressure valves,

i would have been fine with original eqpt if it worked properly and all in safe condition, but that ship had long ago set sail on Hank and what I had was just not acceptable.

Chuck

Of course.