Before starting the resto I struggled a lot with adjusting the 40’s drum brakes. And they did not work very well either. So high priority was to add front disc brakes. Rear discs is not important and you get a rust problem on salted roads. I was lucky and got hold of a set of 42 axles that had been lying around in a garden for some years. Not a beautiful sight, but some sand blasting can do magic. At the same time I found a LJ70 that was sold in parts, and got power steering, brake master and power assist from this. I am not sure if the old 40 drum master could be used, but a disc brake system requires a higher volume of brake fluid than disc brakes to operate so I decided to change to a disc master to avoid problems.
More 40 topics here: land-cruiser-40
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Calipers
The calipers was very rusty and the pistons was completely stuck so I was afraid I had to buy new. But by using a grease gun and soldering a grease nipple onto a brake bleeding screw I managed to pump the pistons out. A grease gun can deliver a very high pressure. Use a clamp and/or peace of wood on the piston that comes first to get both out. Add a clamp on this too, and gradually loosen the clamps as the pistons move.
I had to buy new pistons and split the calipers to allow for honing the cylinders. This is normally not advisable due to possible leakages, but the only way to get these two operable. Toyota do not sell the internal seals, but I found them on the net. These are standard O-rings and easy to source. I have not had any leakage problems, and the brakes operates just fine.
The master and power assist is nearly bolt on, two holes in the firewall has to be moved a few millimeters, and the cylinder rod must be shortened a bit.
Proportioning Valve
Also a proportioning valve is needed to distribute fluid between front and rear, and I fitted one from the 70. This is a load sensing valve that sends more fluid to rear brakes when heavy loaded. Not exactly necessary, but I got it cheap and might as well use it. The valve sits on the right side on a 70 so I had to make a new bracket to get it to the left side.
After practical testing I experienced that the rear wheels blocked before the front wheels when braking hard. This can be dangerous as the rear can swing out and you easily loose control of the car. So I had to fit an inline Wilwood proportioning valve in the rear brake line in addition. This worked fine. To adjust it, find a dirt road, and hit the brakes. Adjust valve until front wheels locks up first.
In retrospect I would not have needed the 70 proportioning valve.
