Well folks, as some of you know I have a 1979 F-700 dump truck. I love this old truck but I have always been fearful of the single circuit master cylinder setup that it came with from the factory....I installed a newly rebuilt master cylinder and hydrovac booster about 8 months ago. Apparently, the booster has gone bad already.
Have any of you ever done a hydroboost conversion and done away with this older style hydrovac setup? I feel certain that this conversion could be done but I don't know much about a hydroboost. I know enough about the hydrovac to want to do something different! LOL!
As always, any information would be greatly appreciated!

 

I have not seen this done, but it should not be that difficult. If I remember right the 1977 Ford truck shop manual shows a hydroboost setup in the B Series used for school busses. So it should be possible to get a listing of the necessary parts from the appropriate parts manual. If you can get access to the shop or parts manual that covers 1979 check out the braking setups available on the B Series. From the firewall forward they are the same as the F Series (500, 600, 750).

 

Ok thanks for the information! I am also curious if I would have to change the wheel cylinders, drums, and shoes as well. My truck has the larger 7 inch shoes on the rear brakes and I think the wheel cylinders are about 1 1/2 inch diameter. I didn't even think about the school busses, though!

 

As long as you stay with the same type of brake fluid, and get a hydroboost master cylinder with close to the same fluid delivery volume as the old master cylinder, you should have no need to change the wheel cylinders. I suggested the B Series setup because the B and F Series brake systems are similar. I have contemplated getting a parts list together for such a swap, but have never had the time to do it.

 

This may sound like a stupid question, but how would I be able find out the volume of my existing master cylinder as well as matching it up to the hydroboost master cylinder? I really appreciate all of your advice! You have a way of making all of this seem POSSIBLE!!! I have done brake upgrades on some of the older muscle cars I have owned over the years, but my dump truck is a whole new bowl of wax for me!!!

 

Actually pretty simple. You should be able to look up or measure the diameter of your existing master cylinder. Then with a bleeder fitting open on a wheel cylinder measure the stroke of the push rod going into the master cylinder. Take half of the diameter, square it, multiply by 3.14, and multiply by the stroke. That is cylinder volume. Do the same for the proposed doner master cylinder. You need enough volume so you can still fully apply the brakes with some shoe wear - too small a volume and you would be pumping the brakes to stop.

Really not much different that what you would do for a car. Hydraulic brakes are not that difficult to figure out on these trucks once you get past a remote booster

 

I know its an old thread but maybe he is still looking for something?

 

I wonder if this ever happened. I have the same truck with the same problems and want the same solution.

 

OP was last on in August of 2017, last post 4/5/2016 looking for brake shoes.

I would suggest a new thread if you want to pursue this idea.