The Stovebolt Site Forums The Parking Lot Big Bolts brake system questions - Dual masters

what is a good donor car for a dual master setup? specifically, I want to go to a part store for the rebuilt masters, and the junkyard for the rest of the hardware. Gus has the 46 1.5 ton brakes in the front and the 52 2 ton brakes in the back.

the brakes fluid that was in the front brake cylinders is so bad that it looks more like axle grease than it does brake fluid. so I figure I should fix the whole system with new lines, new wheel cylinders, and dual masters. I've got the wheel cylinders lined up, but I am not sure what the best choice for dual masters would be.

any suggestions?

(for reference Gus is a 44 1.5 ton with the 52 2 ton 2 spd rear axle)

-Mike R.

Does Gus have a hydrovac?

no Hydrovac, not that I can find. I'll look again tonight and make sure...

casue of the rear axlew change I am never sure of what is and isn't there if I don't go look at it.

-Mike R.

I don't know if hydrovacs were used that early or not. I only ask because converting from single to dual is more complicated if you have a hydrovac.

I would suggest you determine the bore size on your existing master cylinder and try to find a dual master the same size.

Because the rear has been replaced and therefore the rear brakes may not longer match original, I doubt anyone is going to be able to offer a sure-fire right answer...

Mike,

My 44 11/2 ton has vacuum assist, while my '51 two-ton has Hydrovac. I make the distinction as follows:

The 44 has a large vacuum canister, connected to the manifold via vacuum line, which provides added heft to the master cylinder. BUT, it's vacuum assist only - no brake fluid is involved at all. In fact, I could remove the canister mechanically, and not much would change.

The '51 has a somewhat similar-appearing canister, but it is more complicated, as it involves the brake fluid entering and exiting the canister. The master cyliner pumps fluid to the Hydrovac, which then distributes it to the wheels (at least, I think that's the general idea). When you bleed the system, you have to bleed the Hydrovac. If I were to remove the hydrovac, I'd have to bypass it with the fluid lines to maintain any sort of braking ability.

The vacuum assist was an option on "heavy-duty" Chevs in the '40s. I believe the Hydrovac was standard above a certain level in the '50s. Regardless, it's a good thing to have - the general claim is that the Hydrovac does over 70% of the braking if properly maintained.

Now, all that being said, I have nothing to offer about a dual-master set up! sorry.

-Michael S.

so that brings up a good question, is it worth the trouble to go to a dual master, or should I just find a replacement for the single and either add or fix the existing Hydrovac...

first though, I have to find out if I have a Hydrovac at all...

-Mike R.

I don't think it will be hard to find people who will take either side of that question! I'd want to know what you intend to use the truck for... If you wanted a parade-use only type restoration I'd be in favor of leaving it original. If you plan to build a long-haul cruser my bias would be to upgrade the entire brake system.

Have to agree with Oldsub on that. Nobody worried about a single-master system before duals came around. IMHO, the original system will be fine, IF it's gone through carefully and kept in decent shape. AND, have a parking/emergency brake you can trust if the worst happens. I'd get the Hydro working (assuming it has - or had - one!) and rebuild the existing system.

That being said, I agree that if this is a daily long-hauler, a dual system is relatively cheap peace of mind.

-Mike S.

well, no hydrovac, and no vacume boost either.

I accidentally got a replacement Master though, the parts shop ordered the wrong part and I ended up getting a master cylinder instead of a wheel cylinder.

I intend to use it to haul things to farmers markets.. assuming I get my farm going. so I will want to go with the dual masters from the sound of it. I'll use the single for now, and I can always move up to dual later. I am getting new everything related to brakes as I do this. I found a decent parts place where the guy behind the counter is resoring an old vehicle too and has the patience to go through all the books with me to find the parts.

anyway... the real wheel cylinders will be here in about 3-4 days, so I can put my front wheels back together. I'll need to re-read the posts on bench bleeding this new master... hey soon I'll have a brake system, and then I can move on to getting the engine running

-Mike R.