Thanks I checked the MC first thing. unless i take it off and check my self, the supplier and ORiley assured me it is correct. 1"
Installer made the rod to fit this install. I am going to adjust the rod inside, to lengthen the travel and see if that works. maybe the brakes themselves are adjusted to tight as well. I will figure it out. Thanks for your help and all that offered

 

new booster setup





Mechanic tied the vacuum into the existing line off the back of the carb

 

PCV hose goes to that port on back of carb. You need direct vacuum from intake for power brakes.

 

will do Thanks

 

You see that brass fitting with a rubber cap on it? Take that one out and install another fitting that has a nipple on it that the booster hose can clamp on too. Most parts stores have a variety of "weatherhead" fittings. get one there. The intake's hole should be a standard 3/8" pipe thread.

 

 

Yep. That's the spot. Only do it with a new fitting that has the bigger nipple. The booster will be able to react as fast as it should.

 

With using that fitting it's like thr vac booster trying yo breath thru a straw.

 

I replaced that fitting with the proper fitting. although my problem with the brakes still remain

 

If I read your comments correctly, you feel you have too much break too soon?
In the voice of Carl from Sling Blade, " Ahite then, did you check the self adjusters to make sure they're not too tight? mmmhmmm. I like 'em french fried taters"

 

That's the next step, I want to rebuild the brakes anyway.It is straight as an arrow. the interior is in great shape as well.
Next step after the brakes is to remove the bed and work on the frame rust. I am restoring as much as I can.

 

That's not why I wanted you to correct the source of the vacuum. I wanted that for your safety. Brakes are your life. I think it is the booster to M/C rod needing to be adjusted shorter. To Steve's suggestion. Check that 1st.

 

Power brakes don't need as large of a pedal ratio (mechanical advantage) as a manual brake setup. The typical pedal ratio of a manual brake setup is close to 6:1. Typical pedal ratio of a power brake setup is close to 4:1. This is the distance measured between the brake pedal pivot (fulcrum) to the brake pedal pin where the booster input rod attaches.

Unfortunately for most of the Bumpsides and Dentsides, Ford didn't see fit to alter the pedal ratio for the majority of the power brake boosters installed in these trucks.

The input rod to the booster would need to curve downward and the pin on the brake pedal would need to be moved lower than where it is now (roughly 1.250"). Some of the Bumpside boosters had a threaded adjustable input rod. A curved eyelet input rod could be fabricated to thread in place of the straight eyelet. However, the problem then becomes moving the pin lower on the brake pedal for the curved eyelet to attach to. The Bumpside brake pedal curves right in the area where the pedal pin would need to be moved to (this is very easy to do on an early Mustang) but, not so easily accomplished on a Bumpside.

A booster with a bell crank (cantilever) bracket that mounts to the firewall, between the input rod and the booster, will alter the ratio but, many trucks don't have this setup and the ones that do just have single diaphragm boosters, not a dual diaphragm.

If the booster output rod is adjusted too far out, it will keep the brakes partially applied even when the brake pedal isn't being applied. If the booster output rod is adjusted too short, it will make the brake pedal have excessive forward travel before any significant brake force will be applied.

Changing the length of the booster input rod will not change the ratio of the pedal to the booster. It will only change the height of the foot pad on the brake pedal, relative to its distance off of the floor. The only way to change the the pedal ratio here is for the pin to be moved a greater distance away from the pedal fulcrum --but as already explained, not so easy to do with most stock Bumpside/Dentside boosters.

Since reducing the pedal ratio on a Bumpside generally isn't so easily accomplished, the only other means to reduce brake sensitivity is to change the bore diameter of the MC. If the brakes are too sensitve, the bore diameter will need to be increased. --this may require experimenting with several MC diameters before the desired braking is accomplished.

If your current MC has a 1.00" bore, a 1.062" (1-1/16") bore diameter MC would be the next step up. It will have a 6% reduction in output pressure compared to the same amount of force applied to the brake pedal with your current 1.00" MC.

A conventional cast iron MC with a 1-1/16" bore was used on the '78 F250s.

BrakeBest Select NMC1676 - Master Cylinder | O'Reilly Auto Parts

Other than the choices above, the only other alternative is to just get used to the way the brakes are .....or, put discs on the front. Drums are self-energizing. Discs aren't.

 

Hey Ultraranger great info. I'm also changing my booster and I went with the Explorer master cylinder like you. What rod or rod length did you use for the Explorer master cylinder.
For me, with the F250 booster and master cylinder I had before, the rod was 5 1/2" long and with the remanufactured booster I got the rod is 4 1/2".
Should I use the longer rod like before with the Explorer master cylinder or the shorter rod?
It's a difference of 1" and from what I understand if the rod is to long it will keep the brakes applied and to short maybe the pedal will hit the floor?
Thanks
Kenny

 

Thank you for the great explanation. I think I will try the new Mc.
I will get back on the outcome.