Brake proportioning valve
 

I need to replace the brake proportioning valve. I have a 1970 F250 2 wheel drive with front and rear drums. Can I use a proportioning valve that says its for front disc / rear drum? I cannot find one specifically for front drum / rear drum.

Power brakes or no?

What gives you the idea you need a new "brake proportioning/metering valve"
Your vehicle didn't have one from the gate....

You can use one but I wouldn't count on the clamping/stopping power as they were made for disk/drum and wouldn't work right for your application....reservoir volume, metering needle, farting ability, etc.

What you need and these older drum/drum vehicles required was a distribution block....that's all.

Do you have a dual master cylinder? One port to the front, the other to the rear, right?

All 1967 and later F100/350's, Bronco's & Econolines have a dual master cylinder.

C8TZ-2B257-D .. Brake Pressure Differential Valve-Use with Drum Brakes (with/without P/B makes no difference) / Obsolete

Applications: 1968/72 F100/250 2WD & F350.

It is a dual master cylinder and power brakes. Is it possible to get a new distribution block? I'm replacing everything in the brake system from the vacuum booster to the wheel cylinders and all the hardware inside the drums, brake lines, etc.. I assumed it was a proportioning valve but I can't find a distribution block either.

FoMoCo: Brake Pressure Differential Valve that some peeps call (in error) a proportioning valve (see post #4).

It's not referred to as a distribution block.

Pic: Scroll down to 2B257 and read what it says:

Click on the pic twice to expand it, so it will be easier to read the C8TZ-2B257-D applications.

https://cimg8.ibsrv.net/gimg/www.for...111a3a5028.jpg

So what is my best option for replacing it?

Unless someone removed it, or you have brake fluid going everywhere when you press on the brakes. It should be there. Why do you think you need to replace it? But if you really want one, National Parts Depot should have one.

I need to replace it because I removed the old one along with all the brakes lines, vacuum booster, etc... thinking it would be an easy part to replace. Everything was covered in grease and corroded to the point I doubt I would have had success removing the lines.

You don't have to replace it. There's a rebuild seal kit available from Muscle Car Research.

https://www.musclecarresearch.com/valve-kit-whead1

Ok, I need some clarification here, please. With the drum/drum set-up I wasn't aware that these vehicles used the brake pressure differential valve as used with the disk/drum setup.

I've worked on vehicles so equipped (drum/drum) and they weren't running the differential valve, only a distribution "box" from the M/C.

What am I missing? Or am I too far gone to remember this?

Thanks...................?

The block does not alter the master cylinder pressure at all. However if there is pressure change, like a leak in either the front or rear system there is a spool inside that will shuttle to the low pressure side. This would prevent the mater cylinder from going dry and you losing all your braking ability. If it is still functional the brake light on the lower left of the dash would come on alerting you to a problem.

Hope that makes sense and as noted they can be rebuilt.

cstoyer

Thanks, cstoyer.....I'm well aware of the function of these valves, as having rebuilt/replaced a few over the years.

It's just that for the life of me, I didn't think drum/drum vehicles had a "proportioning" valve....a metering/ distribution block, yes but not a disk/drum type valve that was the same for a drum/drum set-up.

I guess I'll have to re-school myself on this.....if I can remember how to read...Hahahaha!

The block was only used on pre-'67 model vehicles with single pot MCs. Beginning in '67, when the drum/drum brake systems were split and used with a tandem MC, the pressure differential valves were added to the brake system.

The block was just a hydraulic manifold. The PDV contained a valve spool.

Ok, ultraranger......thanks for the time dilation clarification on this....:-X22