I have a 1950 1/2ton and doing a front disc conversion. I have ready many threads and have a question. I see the vendors offer a 1" bore but I have also seen 1-1/8" bore for disc/drum conversions. Which size MC is the correct size. Also, should I use 3/16" lines for the front and 1/4" for the rear? The PP valve has two outlets, I see that one outlet is plugged and the only one outlet is used and them TEE to got to the front disc. I also have seen drawings showing the two outlets used one going to each front brake. It seems like instead of having the fronts lines TEEd, It would be better to have individual lines to each front brake. any suggestions would be great. Skipper
The correct bore depends on what calipers you are using for the disk conversion. The volume of the bore compared to the volume of the calipers will set your pedal throw and the diameter (cross section, really) compared to the level arm on your pedal will set your pedal effort.
Are you going to a power and/or firewall mounted system?
As far as using a tee vs both ports on the proportioning valve, it is whatever you want. The two ports are connected internally so it it is basically just a built in tee. I used both ports on mine because that put all of the hardline joints where they were easy to install and inspect.
I've always figured the calipers have a bigger fluid chamber than wheel cylinders. If you're going to increase the size of things, it would be par for the course to increase the tubing size to the front brakes more than the rear. In reality, 3/16" for front and rear is probably fine. It seems to be the standard in cars made today.
A true proportioning valve will have a different pressure output between the fronts and rears, that is the reason to use that type of valve. The line diameter will be dictated by the port/tread size at the MC, proportion valve, and wheel cylinder/caliper.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
My 52 panel....dual MC with small booster mounted under the foor, from Pirate Jack in Asheville N.C. worked great the 7 years I drove it. With the dual MC one chamber is larger than the other and I plumbed the large one to the front brake. Used a 10 lb residual valve on rear brake line. The brakes would stand it on its nose. (Shoes on all 4 wheels)
I am not sure how you can fit a small booster on the MC, there is such little space. I checked the Pirate Jack site but I did not see a kit for the advance truck only for the 60 models. Thats great that you are using the drums all the way around. One reason I am changing to disc is that I have huck brakes and not the bendix brakes.
The proportioning valve seems to have small front outlet threads versus the rear. So perhaps it is meant for smaller lines up front.
Look a little closer- - - - -the metal lines are the same diameter on both ports. The fitting threads are different sizes as a method of "idiot-proofing" the installation so the front and rear lines can't be swapped by a ham-handed wrench jockey. Don't believe things like that can happen? There was a particular power steering gear used on some Mercedes models with the pressure and return lines with the same thread. If the high pressure hose got installed on the upper port, the pump would blow out the seals and empty the reservoir up the steering column and into the interior of the car. Hydraulic fluid IS NOT an appropriate treatment for custom leather upholstery! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Classic Performance Products (CPP) makes a booster that fits under the floor in the stock position - I have been running this for almost a year, and it works incredibly well with my 4 wheel disc setup.
~ Dave 1950 Chevrolet 3600 3/4-ton with 261 engine & T5 Transmission
That is a very slick set up and a 5-speed. I see that using the booster moves the MC further back. Do you know have to make a cut out on the floor of the cab to fill the reservoir?
Dave, loooks like mine did. Didn't know Pirate Jack quite carring them. I will add that I got the bracket from them to that made mounting a piece of cake.
Rc356, let us know what you do and how it works out.
Remote fill reservoirs are available for those "Corvette" style master cylinders.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Classic Performance Products (CPP) makes a booster that fits under the floor in the stock position - I have been running this for almost a year, and it works incredibly well with my 4 wheel disc setup.
Dave, no issues with the T5 hanging out there in the wind? I'm almost thinking of running some struts from the bellhousing to the trans on mine.
Mark, I believe I'd want to run a rear crossmember of some type to support the tailshaft housing. There will be a lot of torque load on the rear U joint area without some support. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Dual master for 4 wheel drums, use a 1 inch master, a 10 pound (red) inline residual valve for each line (wilwood). You can use a distribution block if you want to wire in a brake warning light. No combination valve needed although some use them anyhow. You don’t usually need the proportioning portion of the combo valve.
For a disc drum system, use a 1 1/8 bore master, a 10 pound inline residual valve (red) for the rear brakes. Because the master will likely be lower than the front calipers, or pretty close to that, install a 2 pound (blue) residual valve. Use a combination valve with this set up.
3/16 lines are fine. Front port of master is for front brakes, rear port for rear. Some combo valves have two ports for front brakes, one port for each side. You can run two lines if you choose, or plug one port and run one line similar to stock.
Dave, no issues with the T5 hanging out there in the wind? I'm almost thinking of running some struts from the bellhousing to the trans on mine.
I have asked this same question in the past. Someone, it might have been Lugnutz, mentioned some problem created by supporting the T5 with a crossmember in an early GM truck. Perhaps someone can weigh in with more specifics.
The T5 on my shelf, which is patiently waiting for me to install, is an early S10 tranny. It has those strut rods and I figure there would be no harm installing them. Although I struggle to imagine they do a lot of good.
A heavy as a horse stock 4 speed transmission hangs off the bellhousing unsupported on 3/4 and larger trucks without issue. That aluminum 5 speed will be just fine.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
Weight wouldn't be a concern on my part. Torque on the driveshaft on a hard pull could break that aluminum transmission case in half on a hard pull. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
