Hey gang! I'm installing a vacuum booster under the floor of my '55 F100. I'm leaving the drum brakes front and rear. Do I need to use a residual valve for either front or rear?

 

Not as long as the master cylinder you are using is a drum only MC. Drum only master cylinders have a built in residual valve set at 10 lbs front and rear so you should be all set.

 

OK, and if I'm not using a drum only master cylinder? I think this one is a Corvette type dual res unit. It can be plumbed on the right or left side.

 

The problem with drum brakes are that they fade when hot. Seems like adding a booster will not solve the worst inherent problem with this system. Are you planning to upgrade at least the front brakes to discs soon?

 

It's likely I will go to disc in front eventually. I had a '56 longbed f100 for years, all stock and only had brake fade in extreme situations. Like Jose Wales said, "A man needs to know his limitations." I'm adding the booster to make braking easier, not to solve any problem with the system. Drum brakes are what they are.

 

Power boosters work well with drum brakes. If you want to reduce brake fade you just need to upgrade brake linings. For something this old, most auto parts outlets will only offer a "standard" lining material. If you want better, look for a place that relines truck and bus brakes, or a small to mid size industrial brake rebonder. There are some pretty decent brake lining materials out there that will make your drum brakes perform better than you would expect.

 

With that MC you are going to need 10 lb residual valves both front AND rear as that MC was probably made for use with four wheel disc brakes...

 

That is my plan. It looks like I will need to use a metering valve on the front also. I'll be looking into some premium shoes and also some sort of air vent design for the backing plates.