The Stovebolt Site Forums The Parking Lot Big Bolts BRAKES ON A 1952 4400

I JUST GOT MY BARN FIND 4400 BACK ON THE ROAD AFTER 20 PLUS YEARS AND NEED A LITTLE OPINION/ FACTS ON BRAKE PERFORMANCE. NEW WHEEL CYLINDERS FRONT AND BACK, MANUAL CORVETTE 1 INCH DUAL MASTER, 10LBS RESIDUAL VALVES AND A ADJUSTABLE PROPORTIONAL REAR VALVE.AND BRAKE HOSES. I ADJUSTED THE SHOES TO THE POINT WHERE THE TEMPERATURE IS WITHIN 10 DEGREE OF EACH OTHER ON A HARD STOP. WHAT EVER I DO I CAN NOT GET THE BRAKES TO LOCK UP FOR A PANIC STOP. THE REAR BRAKES DO HAVE 2 WHEEL CYLINDERS EACH WHEEL .SO WHAT I AM ASKING IS IT POSSBLE TO GET THE BRAKES TO PERFORM BETTER. THE TRUCK DOES STOP AND DOES NOT GET FADE THE DRUMS ARE NOT WARPED AND THE PEDAL IS FIRM BUT NOT STONE HARD.

welcome to the site! Is your master cylinder the same inner diameter as the old one? Also, does this truck have a hydrovac, and if so, is it working properly?

p.s. it is considered yelling to type in all caps, plus it is harder to read.

Rich, I think your master is too small. I believe you should have an 1 1/4" or 1 3/8" bore. Don't be afraid to use a bore listed as a metric bore of 32-36mm. You need to be pushing more volume. I tried a lot of master's when making my disc brake conversion for these larger trucks. I settled on these numbers from Carquest...

-Booster 5471098 1994-1996 Chevy 2500 gas
-Master E151640 1996-2002 2500-3500 Express van

Hope that helps.

I started with a 1 1/4 piston, like the factory one, but dual, the petal was so hard once the system was bleed, the push rod bent, So I went down to a 1" and the petal was better. If I go down any smaller the pressure will be higher with no volume, if go larger the petal might not even move. There is no hyravac assist.I was thinking of moving the master farther back and installing a 7" vacuum booster, but the fill hole will have to be under the seat. I had to move the master back to fit the brakes lines one the side.

doing a bit of math, the original bore was 1 1/4", but that 1 1/4" fed all 4 wheels. Since you are using a dual cylinder, you want roughly half the volume on each cylinder (probably more like 65-70% on the rear since, like on mine, I have 2 cylinders on each rear wheel and one on each front) but you get the idea.

I think you are probably fairly close and are on the right track with adding a booster. Once yo uadd a booster, you may want to put the larger bore master back on.

anyone retrofit 7inch booster under the floor with the sm420. the brake on the tailshaft crowds the master and the booster.i already had to space out the master itself now i need 3 more inches and cut a access under the floor

If the pushrod bent it is a poor design. The brake MC mount and any linkage should withstand all the foot stomping you can give it.

I don't see how the original would bend or fail in use, your replacement should be just as good.

My 46 is a little different design. When you push the brake pedal, it moves the rod forward. I think yours moves it back! I have the GKT134 trans. Not sure of the size difference.

http://s1006.photobucket.com/user/r...Conversion/IMG_1229_zps959455b2.jpg.html

My '50 4100 has a 1.25" bore m/c, the front wheel cyls are 1.25" and the rears are 1.5". Originally it had a hydrovac unit on it also. I rebuilt everything and bypassed the hydrovac and I have PLENTY of brakes. In fact, it'll lock the wheels down, no problem.

Thank you mechanic58 I have a 1 1/4 ready to installed, just waiting for a vacuum booster to come in. Is your pedal real firm or is mushy or is it what I hope a comfortable and you can feel your braking power?

The pedal is very firm. In fact, I kinda have to be careful about how vigorously I step on it, sometimes it'll lock up the rears pretty easy. It needs an adjustable proportioning valve since I don't usually drive this truck around with a big load on it.

Well I installed a 1 1/4 g30 master and a 7" booster.The pedal is a lot easier, It goes down a third before the brakes start to work. Stopping better, I have the shoes adjusted real close. If I go back 3 clicks ,like manual states, on the adjusters I get crappy braking.

After adjusting the push rod nipple on the dual diaphragm booster out to .513" and installing a 41-46 factory vacuum spacer port, the brakes are firm and stop on a dime w/ empty payload and exceptable with a load.

after multiply adjustments on the shoes and the little shaft on the booster and a 200 mile break in, the truck stops like a new truck. a total success.