Well, I've turned two trash heap T-Vs and a pile of spare parts into two things of beauty. I had only done slide valve rebuilds made from 1954 through 1955. They must have discovered that those models became pretty useless because they quit making them, altogether. The slide valve refers to the means the vacuum is turned on by one cylinder moving inside another until their vacuum ports line up as you move the pedal lightly with your foot. There's about 3/8" of movement to make the vacuum passages line up. Once vacuum is allowed into the cylinder vacuum pulls the power piston away from you and into the cylinder pushing the rod that displaces brake fluid in the master cylinder. That's power assist.
When the rod enters the master cylinder it displaces fluid in the chamber. The only place it can go is out to the wheel cylinders where the pressurized brake fluid causes the brake shoes to be pushed apart with their abrasive material rubbing on the inside of an iron or steel brake drum creating the friction necessary to stop the car. As soon as you let off the brakes vacuum is shut off and the forward movement of the stainless steel rod slowly stops and is pushed all of the way out of the master cylinder by another force, spring pressure, pulling both brake shoes to their rests on all 4 wheels. That spring energy is converted to hydraulic pressure that returns the rod to its most retracted position by pushing the fluid back into the master cylinder under pressure. There is a device that makes the return of the pedal slowly return to normal position. When the return process in completed a washer on the end of the rod trips the tilt switch, opening the means for fresh fluid to flow into the master cylinder, compensating for the loss of brake fluid while driving. If your tilt switch is not being activated your fluid is not being topped off automatically.
I used the hose clamps provided on the cast rubber vacuum hose. If you used water or fuel line they will collapse the moment you start the engine. It's designed for pressure, not vacuum. You can use a hose clamp on the power piston side of the hose, but using a spiral clamp on the check-valve side the shuttle cannot fully retract to open the compensating valve because the clamp thickness lessens the travel the compensating valve needs. That 1/32" makes a difference.
The sleeve valve was a great car stopper to begin with, but the tiniest bit of wear would ruin braking capacity until you had nothing but a big vacuum leak which badly affected the way the car ran and the way anything with a vacuum motor operated. Antenna, heating and cooling controls and wipers would all be affected, even the way the car ran as low vacuum affects timing. The poppet type used in '56 and '57 was an answer to a problem no one knew they had. The only whole units available after the beginning of 1956 were poppet type, a much more effective way of turning the vacuum on and off with the tap of the brake pedal. They lasted considerably longer than the sleeve-valve. I'm surmising that maybe 5% of the sleeve valve remain.
I was fortunate enough to have been given a Treadle-Vac when Mad Scientist walked amongst us. He inherited the family's Mark II and turned it into an admitted FrankenMark, changing every single system he could. He describe it as sadly neglected in need of some electronics. He solved the low fuel relay that did, electronically, what the original did with very fragile components. He was my hero, and my antagonist at the same time. He asked me one day if I would like a brand new Treadle-Vac he had no use for, digging it in that he had gone the disc-brake dual master cylinder route of his own design . I might have trusted what he designed. I stuck the T-V on the shelf. It had a Ford part number and the unit was stamped F specifically for the Mark II. It was a galvanized vacuum chamber and no green plating on the MC. It had a Continental part number in a dark crayon on the zinc plated canister. Now I have to see if I took pictures. The other two T-Vs came to me in exchange for an original metal filler hose that looked new. Until he reminded me that he had traded me the two units I could offer no help to Chris in his quest for solving his braking dilemma. He needed a working T-V to reverse brake work done by a previous owner that no one could make work right. He needed a core and offered decent money for one. He also made an offer for a unit rebuilt. I tore open the box of two I had forgotten about and found that could make 2 out the best parts of 3 and found that Harmon Classic Brakes offered the most complete kits I had ever seen. I had Chris order kits for two complete units had them delivered to our house. I set about messing up every plan I had for a 2 week period while I media blasted all the parts, even treating the zinc die cast master cylinders to glass beading that left them better looking than new. The kits were missing a couple of gaskets that I easily made, but it was very complete, overall.
I swore 10 years ago that I'd never work on anything with a deadline, but there I was. He was hoping to get the brakes working right before its appointment with an upholsterer and I set about making it happen.
It was just as easy to build two side by side, but did a boat load of preliminary work to get to the assembly. After chasing every thread and wire brushing every fastener I was able to get his out the door as I took a breath of relief. The second T-V is going in my Mark II to replace the acid-damaged unit. I will rebuild that sleeve valve unit and will install it, even for a short time so I can report on a new to new comparison.
I hope this resolves Chris' brake-bias problem. If I were younger I'd start a business reversing disc brake and dual master conversions for people tired of standing their car on their nose every time they hit the pedal. I wish there was a way for people to compare new drum to new disc before throwing a parts package at a car put together by a retailer that's not a brake engineer. I'm not one, but I don't claim to know everything. What I do know is that properly set up factory brakes will serve you well using the best engineering of the time. Having an operable emergency emergency brake resolves 90% of the safety issues and new flexible brake lines solves the other 10%. In fact, the US banned lawn darts as too dangerous, but drum brakes are still used extensively on semis and the rears of many production cars. Why is that?
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Barry Wolk
Farmington Hills, MI
C5681126
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Originally Posted by Barry Wolk
