I think if you pull all the original stuff you are probably OK. From what I was able to read, the 1978 valve should have this metering capability built into it. I think this thread applies - https://www.ford-trucks.com/forums/1...valve-pic.html

 

Thanks for your help

 

This is what I used. It's kind of nice being able to adjust the rear brakes to help balance the truck.

It's $90, but it fit right place in and works well.

https://www.summitracing.com/parts/w...SABEgIUl_D_BwE

 

Hey Surveywaters. Some good info, but I'll add a little bit of my experiences with this type of project too.
And I'll add that to at least a limited degree every truck is a little different, so the old "your results may vary" saying certainly can apply.

With Ford disc brakes, depending on which ones you utilize, the caliper pistons are actually kind of small compared to many. So the 1" master size is not completely out of line. I don't disagree with what was said so far, and for our customers we typically sell 1.125" masters fro just about every boosted application. Firmer pedals are good, but the big reason is lots of our Bronco customers use GM truck calipers with a notably larger piston size. So the slight extra size works well as long as you have a good booster. But that's the other kicker. With so many Ford boosters being quite small, the available boost is not exactly what you'd call massive until you get to the larger diameter models, or hydroboost. But lots of members here have more experience swapping booster models than I ever will. Usually with pretty good results from what I've read.
But as an FYI, my '79 F350 with monster rear drums and the big dual-piston calipers up front still uses a 1" master cylinder. Even with it's larger diameter booster too, which for many years was the go-to upgrade for Ford truck owners with the smaller boosters. But now they're like hen's teeth, so you almost always have to have yours rebuilt rather than just going down to the local store to buy a new one. Too bad too, but that's what finally made my decision to go hydroboost if I can.

With our vintage Fords, at least the ones I'm familiar with, the residual pressure check valves are located inside the ports of the master. Most modern replacement masters don't even come with them anymore, because their primary function was, as mentioned earlier, a hold-over from when master cylinders were typically mounted down low. So low that fluid back-flow was a problem. But if you think about it, the part about them keeping the shoes closer to the drum is kind of problematic. The springs are usually so stiff that no check valve can keep a drum brake shoe from being pulled all the way back to the central anchor and pivot points. Maybe they'll hold off retracting for a few seconds, but eventually they will always come back to rest all the way back. Only proper adjustment guarantees that the shoes stay close enough to the drum to do any good. Which is why we always hope out auto-adjusters work properly! (which many of mine did not unfortunately).

To add discs to your front, you will remove the check valve completely from your front brake port. It's not really a matter of replacing it with a 2psi version in most cases. It's just getting rid of the old one completely, while leaving the one in the rear circuit intact if you want.
If you happen to have a brake system with external check valves, then great you can remove and/or replace the one for the discs with a 2psi version. But with most Fords I'm familiar with, if you have an older master you can verify the presence of a check valve by gently probing through the orifice in the seat with a poker of some kind. If you feel a spring loaded thingy inside, you've got one. If your poker/prodder tool just goes straight in with no resistance, you likely don't even have one.
To remove the old one I've always just used a sheet metal screw of the proper size to just thread into the brass seat (the cone shaped bit under the line fitting) then pull the cone seat out to access the check valve parts. Pull out the spring, the rubber seal and the steel ball if it has one, and then re-insert the cone seat. Install the hose/line again and you're in business.
Most, if not all Fords have the front brakes plumbed to the rear-most port. Not all manufacturers do it this way, and maybe Ford didn't always do it either, but all the trucks I've known were plumbed that way.
If you would prefer a check valve in both circuits, they area available from different sources as separate in-line fixtures. I've often thought of using them, but never have.

Regarding the proportioning/combination valves, this is another bit that is not etched in stone. And this is where I always go into the way the trucks are set up and what it's being used for. Are you going to be a street cruiser, or a wood hauler? Are you going to auto-cross it, or daily-drive it?
The combo valves are very nice to have, but not an absolute necessity depending on how the truck is set up. If it's well balanced now, and the rear brakes are not too large or powerful, then you might even try driving it as-is with just the distribution block and no prop valve. My '71 Bronco is done this way with manual brakes (1" master) Ford F150 front discs, stock 11" rear drums, but with the next size larger wheel cylinder. Stops on a dime and is super stable and, unlike most people recommend, my rears lock up just a tiny bit before my fronts. I know the logic of not wanting to swap ends, but mine does not tend to slide out of control when the rears are locked up and they give me a good indication when the fronts are near their limit. I can handle a skid, but I hate it when the fronts are locked and you have to modulate the brakes even more carefully because locking the fronts to me is totally out of control!

I'm a big proponent of the manually adjustable prop valve that Cleveland is talking about. Not only are the aftermarket combo valves prone to leaking out of the hold-off / delay valve, but if the use of your truck is varied, this allows you to fine-tune when your rears start reaching the limit. I've got no prop valve on my '71 with the Ford brakes, but a manually adjustable Wilwood on my '68 with the GM calipers.

Hope I didn't just add confusion to this discussion. But my experiences have been what they've been, and so far everything has worked out well. I don't know what front brakes you'll be using, but some of this might come in handy.

Good luck!

Paul

 

Thanks. I have an aftermarket 1" master cylinder with a 7" vacuum booster. The check valves are inline, not in the MC. The rear drums are the original '69. The front are factory '78 F150. I'll try just removing the front.

 

Cool. So are your valves factory, or were they installed later?
Definitely post up a pic if you can. I'd like to see them either way, but especially if factory!

Thanks

Paul

 

This is the last up I bought


https://www.ebay.com/itm/202339016126