The Stovebolt Site Forums The Parking Lot Big Bolts 1967 Chevy C-50 with Ford F600 Master Cylinder?

A few months ago I pulled a 1967 Chevy C-50 out of my neighbors woods, and have been slowly working on getting it going. It has a 350 engine, SM420 transmission, the two speed rear end, and the single reservoir master cylinder with a single under cab brake booster.

When I went to work on the brakes, I noticed that someone had welded together an adapter plate and had used a Ford F600 master cylinder (Rockauto PN F22977 for $100, also known as Bendix 11129).

From some searching I did here on the board, it looks like Napa part UP 36229 ($160) was stock on this truck.

Did people commonly adapt over to the Ford master cylinder to save money? And does anyone know if there are downsides to doing this? Both are 1.5" bore, but I am unsure if they have similar throw distances.

I know I am going to have to replace my master cylinder (and probably rebuild my Midland Hy-Power booster) but I figure that if I am going to do it, I might as well do it right the first time.

I see no advantage or disadvantage, depends on what you want to pay for a master cylinder, and if you like looking at an adapter.

Depending on your intended use, you may consider swapping to a dual circuit master cylinder and run two boosters under the cab, one for front and one for rear. Or a firewall mounted booster before the dual circuit master cylinder.

You say you will do it right the first time. That would either be the correct Chevy master, or a newer dual circuit master, depending on if you plan to use the truck or not.

Grigg

I wanted to run a dual circuit master cylinder with a firewall mounted booster, but when I searched I couldn't find any information about it.

I tried looking in my dealer service and overhaul manual for part numbers, but it said that the 1967 C50 never had the option for a dual circuit master cylinder.

Also, the biggest dual circuit drum/drum master cylinder I could find was a Bendix 11331 with a 1 1/8th inch bore, made for 1970 C30 trucks. The rear brakes on the C50 are huge, and are twice as large as the front. I was not sure if this master cylinder would work with brakes like that so I just gave up on the idea.

Some people said it was OK to use disc/drum dual circuit master cylinders with drum/drum brakes as long as you use residual pressure valves, but there seemed to be some arguing about whether it worked good or not.

The biggest disc/drum master cylinder I could find was a Bendix 11584 with a 1 5/16" bore. While this is usually mated to a hydroboost (power steering pump) assisted brake system, they can also be bolted up to a normal firewall mounted vacuum brake booster.

Any insight into what dual circuit master cylinders would work would be greatly appreciated.

Thanks

Well, I think I may have found a solution. Here is my thought process:

Problem:
In a single circuit system the wheel cylinders all expect to be at the same PSI when braking. The front to rear brake balance was set by carefully chosing wheel cylinder sizes.

If you convert to a dual circuit system, uneven braking could occur because the front and rear brakes use very different volumes of fluid, and would build pressure at different rates.

Solution:
Split the brakes up diagonally. By doing it this way each circuit should require the same volume of fluid, and all should build up pressure like they would normally in a single circuit system.

It would probably also be safer to split them up diagonally so I would never lose both (huge) rear brakes at the same time.

The key to this plan is just making sure that both chambers in the master cylinder are sized the same. I guess this was common with drum/drum dual circuit master cylinders, so hopefully it will not be an issue.

I will probably just pick up a refurbished master cylinder for $33 (R12700, it should work with a firewall vacuum booster I have on hand), and see what happens.

I will also pick up two brake pressure gauges so I can see how well this all works.

Swapfile check out some mid 80's 60series in the
salvage yards .I have 2 that are equiped with dual
master cyl & Hydraboost they also have electric backup pump. About 2 years ago we swaped this system into a 1968 C60 worked excellent. Also some
F---s and IH's had this system. There is another
booster system out there that has a vacuum booster
before the Hyraboost these are mainly on school busses. I also owned a 80 F700 that had just a very large diaphram booster & dual master cly mounted on the firewall, this also worked well.
As far as using a disk master on a drum system as long as a residual pressure valve is used no problems will occur

Have A Good Day -----FERGY

I don't think splitting the brakes diagonally is a good idea. The trick in splitting to a dual master is the balance of front versus rear brakes, and a diagonal split means you have that challenge twice.

I would investigate the master cylinders used on '68 to '71 trucks. The dual master became a Federal requirement during that period and the switch to disk brakes began in '71. I'm sure you'll find that something in that period at least gives you the right specs.

A residual valve serves two purposes.

One is to keep brake fluid from all running back into the reservoir and that only matters if it is below the wheel cylinders. That would not be the case in your '67 C50.

The second purpose is to keep the brakes ready to apply. For drums, that's keep some pressure on the springs, for disks its keeping the pads close to the rotor.

The issue is to hold the shoes against the brake springs you need about 10 pounds. That much pressure will actually apply disk brakes, so they need much less pressure, usually 2 pounds.

Your application should have 10 pound valves in both the front and rear circuit, though it may not be critical and the residual valves may in built into any master cylinder you buy.

Getting the balance between front and rear right can be handled with a porportioning valve. That valve will allow you to limit the pressure to the rear to prevent the rears from locking up before the fronts.

If you can choose a master with bores the same as the stock one that is probably not an issue either.

My experience with the cheep rebuilt master cylinders is that they all leak. Everyone I've ever bought leaks from the rear portion into the front, requiring frequent refilling and bleeding of the rear brakes. I'll never buy a cheap rebuilt master again.

I was doing some more work on the brakes, and here are some more part numbers I found:

Front Left Wheel Cylinder 7/8"
Bendix 33406 $50

Front Right Wheel Cylinder 7/8"
Bendix 33407 $50

Front Wheel Cylinder Kit 7/8"
Bendix 66820 $9 (both sides the same)

Rear Wheel Cylinder 1.5" Kit (4 Total Required)
ACDelco 18G20 $6
These are made for an F600, but is apparently the same. I found the part number on the seals that are currently on the truck.

I was unable to find a place to purchase new rear wheel cylinders. All of my wheel cylinders are in relatively good shape (except for the rubber), so I am just going to buy rebuild kits for all of them.

All the lines were rusting or rotting away, and many were filled with junk, so I am replacing it all.

I am picking up 50 feet of bulk brake line at Mc-Master Carr, and a bunch of AN3 fittings, hoses, and adapters from Summit Racing.

Hopefully the part numbers will be useful to others in the future.

Did you have 1/4" brake lines?
I would think you did, and AN4 would be 1/4". AN3 may be to restrictive?

Yeah, my stock brake lines were 1/4" OD, but...

1/4" OD brake lines are .194" ID, which works out to have a cross section area of .0295 square inches.

3/16" OD brake lines are .132" ID, which works out to have a cross section area of .0136 square inches.

Since I will be running two lines to the rear brakes now, it works out to be .0273 (.0136 * 2) versus .0295, which is only about 7.5% smaller than a single 1/4" OD line. I do not think it will be an issue.

Side note:
I never noticed just how big the dual rear wheel cylinders were until I pulled them out and sat them next to the single front cylinder:

[img]http://img412.imageshack.us/img412/6191/mastersmalllh8.jpg[/img]

They are huge!

I did some more cross referencing, and found some more part numbers:

14"x2.5" Front Brake Shoes - $65 for a set for 4
Normal - Raybestos 109RR
Premium - Raybestos 109PG

I guess there was also an option for larger 15x3 brakes. I do not have these on my C50.

15"x3" Front Brake Shoes
Normal - Raybestos 134PG
Premium - Raybestos 134RR

Still no luck on the rear shoes, but luckily my rear shoes are still in good shape.

Worst case, I could probably reline them myself like I did with the parking brake, but I am not sure I trust my own work that much... yet.

No information on front or rear drums yet, but they are pretty beefy and should be able to be machined again if needed.

When I got the truck I noticed it had a snapped off front wheel stud. Napa said they didn't have and couldn't get the stud, and the GMC dealership said they no longer carried it.

I went to an International truck dealer, and while they didn't have the parts, they were able to give me some part numbers. These part numbers are able to be cross referenced back to Napa orderable parts.

Front Wheel Stud
Euclid E-5682
Budd 82525
GMC 3763619
Gunite K46009
NWRA X-1108

Rear Wheel Stud
Euclid E-5683
Budd 82526
GMC 3765876
Gunite 46009
NWRA X-1109

Lug Nut
Euclid E-5734
Budd 81269
Dorman 611-043
Firestone NT-30
GMC 3771410
Gunite 45681
Gunite K-45681
NWRA X-1110
Std. Forge 303119
Trailmobile 21-W182
Trailmobile 38-5734
World Truck 1338002

Another interesting note:

Raybestos lists part number MC34403 has a stock 1 1/8th inch single circuit brake master cylinder for use with non-power brakes. Napa carries this both new ($75), and remanufactured ($35).

If you have a master cylinder/hydraulic clutch combo, it is part number MC19089 for $200.