Front Drum to Disc Swap - same proportioning valve?

[seven-t]

I'm changing the front drum brakes on my newly-purchased '70 F250 to disc brakes; I pulled the complete ibeams and spindles from an early '71 F250 donor truck (**note: I brought a printout of the removal instructions from the Fordification tech section - great work!**).

Question: Is it likely that the proportioning valve is the same for drum and disc brakes? (I didn't pull one from the donor truck.)

I ordered new front rubber brake hoses, plus a set of axle pivot bushings and radius arm bushings. The steering links were missing on the donor truck, but the pitman arm appeared to be the same as what's on my truck, so I believe I'm good there . . . (I also pulled a Bendix power steering box and pump, which will be my next project after the brakes).

Any recomendations? Thoughts?
Thanks.

[fordman]

no you need the donor portioning valve. the old distribution block is just a pass thru kind of thiing it doesn't regulate pressure from front to back like a proportioning valve does.

[FORDification]

Drum brakes have a distribution block....basically nothing more than a tee. Disc brakes have a proportioning valve. If you swap to disc brakes, you need to throw away the drum-brake distribution block and install the proper proportioning valve.

[seven-t]

Well, glad I asked. Great info. So, can I re-use the steel brake lines on my existing truck, swap 'em from the distribution block to the valve? (the donor truck's lines had been snipped below the master if I recall correctly . . . )

[72stepside]

That's what I did. I had to replace the lines from the master cylinder to the valve cause I didn't like how they fit.

[FORDification]

Well, the distribution block is typically mounted on top of the steering box or on the rear of the main crossmember, so your existing drum-brake lines won't work. You can get the lines from the donor truck, but considering how you could completely replumb all the hard lines in the braking system for about $30 in materials and an afternoon's worth of work, I'd highly suggest going this route.

[seven-t]

Uh, yeah, but I've never made brake line fittings...

I just grabbed a flashlight and climbed under the truck (btw; does it matter that the current truck as POWER disc brakes?)

The 'block' is mounted to the inner left frame rail, just behind/below the steering box. 5 fittings. 1 line from the master at the bottom, opposing that is the line which runs to the rear brakes. Line 2 from the master is at the 'top' of the block, which appears to "t" to the two front brakes. Between the two incoming lines is a sender (broken, no wonder the brake warning light doesn't work!)

Thanks. Ken.

'70 F250 - soon (hopefully) to be a reliable tow vehicle!

[FORDification]

Uh, yeah, but I've never made brake line fittings...

There's nothing to it, providing you have the proper double-flare tool, available at any auto parts store. Check out the following link:

http://www.fordification.com/my67-p34.htm

I just grabbed a flashlight and climbed under the truck (btw; does it matter that the current truck as POWER disc brakes?)

No, it make no difference to the braking system...it has no idea whether there's a power booster installed or not.

The 'block' is mounted to the inner left frame rail, just behind/below the steering box. 5 fittings. 1 line from the master at the bottom, opposing that is the line which runs to the rear brakes. Line 2 from the master is at the 'top' of the block, which appears to "t" to the two front brakes. Between the two incoming lines is a sender (broken, no wonder the brake warning light doesn't work!)...

That's the manual-drum distribution block. It won't work with disc brakes.

[seven-t]

Alright, I'll give it a try (though now I'm thinking I might wait 'till after my next race in the event I have a problem with the swap).

Last question, I think: Is the valve ever located somewhere else besides on top of the steering box? I ask this because from the donor truck I also pulled a bendix box and power steering pump and definitely did not encounter the valve . . .

Ken

[FORDification]

The prop valve is normally located on top of the steering box on the '73-'77 trucks, and on the back of the crossmember on the '78-'79 trucks.

Even with all the '67-'72 trucks I've parted out, I haven't found an F250 with factory disc brakes (they weren't available on F100s until '73). However, I believe the factory prop valve might be in the same location as the drum-brake distribution box...but it'll be a different-looking piece from the '73-up version. Here's what a prop valve from a '72 Camper Special with factory discs looks like. At least this is what I THINK it looks like...I saved this pic from an E-bay auction, and it was identified as such:

[seven-t]

I'll head back to the boneyard and pull the valve, then confirm what it looks like and its location (and post a photo, too).

[rjewkes]

the 77 i had, had tha prop valve on the backside of the engine crossmember.

[FORDification]

It was a mid-year change...they would've been put on the back of the front crossmember halfway through the '77 production year.

[seven-t]

I pulled the (factory) disc brake hardware from a '69 and '71. The donor trucks had a distribution block AND a proportion(?) valve (the one shown in Keith's photo above) for the front brakes (it appeared to be the same distribution block as the drum brake set-up, with one of the front line 'outputs' blocked-off). It was a true "bolt-on" swap.

One hiccup, however, was that the new rubber brakes hoses I bought had larger fittings than what were in the calipers. Was there a change in the calipers (4 piston Dayton) along the way?

- - -

Anyone know whether the power brake master cylinders are the same - that is, factory drum vs factory disc?

Finally, should anyone be interested I have a spare proportion valve...

Ken

[seven-t]

Btw - if it'll help your tech section I can shoot and send photos of the distribution block and proportioning valve (for what it's worth, given the location of the valve I do not believe it regulates between the front and rear brakes... but rather it balances between the front left and front right).