I asked about this in my build thread, My "new" truck, but only got one reply. So I'll start a new thread.

I see from Advanced Searches this topic has been covered over and over again. But after reading many (not all) of those threads, I am still uncertain what I need to convert my truck to the dual chamber master cylinder. I'm concerned about the push rod length.

Here's what I have, and what I want to have:

Have:
'65 F250 4x2 power assist 4 wheel drum brakes with the single chamber master cylinder. (see pic)

Want to have:
Power assist 4 wheel drum brakes with a dual chamber master cylinder.

I don't want to convert to front disks. I don't want to change the booster. I don't want to search for a junkyard donor.

I want to bolt on a dual chamber master cylinder and run new brake lines adding a proportioning valve (or whatever it's called) and a tee for the brake light switch.

As always, any answers are appreciated.

RockAuto has a dual chamber master cylinder for a '68 -'72 - 4 wheel drums and power. Will that use the same push rod as the single chamber power brakes I have now? Does anyone know if I can bolt that m/c on to my booster?

CARDONE SELECT 131388 {#D3TZ2140P, M83579} w/ Reservoir
Front Drum brakes; Rear Drum brakes; Power brakes

https://www.rockauto.com/en/catalog/...+cylinder,1836

Here's what I have:

 

Well, I can tell you what I have but it's not the same as you wish. I have '76 dual piston calipers and bought a master cylinder/booster assy for a '76. Replaced all the brake hoses(had to use a rear hose from a 4WD??) for the same '76 year model. The rear end is out of an '81 F350 SRW(huge drum brakes). The results are absolutely amazing. I've been driving Fords for nearly 40 years and have realized none have awesome brakes, but the above combo is right on the money.
My suggestion is to find out if any newer trucks had the same size brake cylinders and drums as yours, but had the dual res. M/C ('69 - up I think). You want to try and match that stuff as close as possible. E.G. If you have 2.5 x 12" drums front / back and a '69 has the same, get the M/C for that application.

 

1961/65 F250 2WD's have 12 1/8" x 2" front/rear drum brakes. Ditto 1966/72 F250 2WD's except Camper Specials and with a 7,500 GVWR

1966/72 F250 Camper Specials and F250 2WD's with a 7,500 lbs. GVWR have 12" x 2 1/2" front/rear drum brakes.

Dual reservoir master cylinders were introduced in 1967.

 

Bill, Does that mean all 66/72 Camper Specials have 7,500 GVWR?

OP, Looks like once you determine your GVWR you buy a M/C from a '67 accordingly and you're set to go.

 

No, it just refers to the fact that 1966/72 F250 Camper Specials and F250 2WD's (except Camper Specials) with a 7,500 lbs. GVWR have 12" x 2 1/2" brakes.

 

Thanks Bill. So if I'm reading this correctly, my 65 F250 2WD with 7500 GVWR has 12 1/8" x 2" brakes all around. This truck, if a 66, would have the wider shoes. N'est ce pas?

Therefore (now my assumptions will get dangerous) a master cylinder for a 68 F250 2WD should work on my truck. I choose 68, because I can't find a new dual chamber m/c for a 67 that states it is for 4 wheel drums AND a power booster.

 

Thanks Prostock.

I think Bill has covered this in his reply. Since my 65 2WD F250 has the narrower shoes, the dual chamber m/c from a 68 should work if it's designated for power assist, which is what I have now.

 

As I'm searching online for a new dual chamber m/c, I notice the pictures of ALL of the supposed replacements for a 68 F250 2WD with power 4 wheel drum brakes have the different sized chambers, which I think are for front disks and rear drums.

What am I missing? Is it possible, as stated by RockAuto, that the pic doesn't necessarily match the part, and the m/c will have same sized chambers?

NAPA



RockAuto



Advanced Auto Parts

 

The booster on your truck looks a great deal like the stock booster on a Galaxie from '65. I wonder if a M/C from a Galaxie would fit your needs? they also had 4 wheel drums, and the GVW was about the same.

 

Thanks James.

Unless I'm mistaken, dual chamber master cylinders were first available in '67, at least for the trucks. Maybe the cars had them in '65?

I did a search after I read this to see what showed for '65 Galaxie m/c, and the ones I saw are single chamber, like what I have now.

My F250 has a GVWR of 7500 pounds, so I imagine that's higher than on a Galaxie.

My daddy owned a brand new '65 Galaxie. He traded in his '62 T-bird for it. I was sorry to see the T-bird go...

 

You might want to PM Ultraranger. He seems to be the resident expert on brakes. He usually hanging out at the Bumpsides forum.

 

Federal laws mandated in 1967 that all U.S. domestic vehicle manufactures replace the single (suicide) reservoir MCs with tandem MCs. This is also when the brake pressure differential valve with brake warning light came into being. '67s had a one wire switch in the PDV. '68 and beyond had a two wire pressure switch.

No Ford light duty trucks came from the factory with (optional) front discs until 1968. Front discs were only optional on '68-'72 F250 and F350 trucks. No factory front discs available on any '67-'72 F100s. Power brakes was optional on any of the '67-'72 model trucks.

'67-'72 F100, F250 or F350 with 4-wheel drum brakes would have come with a MC bore diameter of 1.00". A '68-'72 F250/F350 with factory power front discs would have had a MC bore diameter of 1-1/4".

If you're keeping power all-wheel drums, it'll be best to stay with a 1.00" bore MC. A MC bore diameter greater than 1.00" is likely to present more difficulty in putting sufficient force on the brake pedal, to get the truck to stop within a reasonable distance.

My '69 F100 had manual 4-wheel drums when I got it in April, 2011. A few months later (2012), I added a '75 F350 dual diaphragm booster with a 1.00" bore cast iron MC. This proved to be an overly sensitive setup. In 2014, I replaced the front drums with '77 F100 front discs and replaced the conventional 1.00" bore cast iron MC with a more modern '95 Explorer 1-1/16" bore aluminum MC. This combination has proven to work exceedingly well.

 

Thanks for all this information Steve. After KO1960 remarked that I should contact you, I revised my advanced search for posts about master cylinders with your name only, and gathered much of this already this morning.

And I noticed in one of your pics, the m/c you showed with your 69 F100 all drum setup was the smaller front/larger rear chamber m/c I see in the pics from all vendors of new m/c's. So I take it, that works without having front disc brakes. I'm starting to think that's the only style "new" master cylinder available.



So I think the only other question I have is about bolting the new m/c to the booster. I read several comments about push rod length, but I don't know if that applies in my situation, since I only want to change the m/c and not the booster. The only reference I can find in the Illustrations parts manual is this one, which doesn't show the m/c and booster separated. The push rod part number 2143 shows differing lengths in the parts Text manual, but I don't see one specifically for the booster to master cylinder. And the Brakes section of the Shop Manual doesn't help.




.

 

I'm not certain what the booster output rod looks like on a Slick (?) --I've never actually seen a Slick booster in person. I'm used to dealing with brake parts from Bumps and Dents.

If the output rod on the booster for a Slick is like the ones on the Bumps/Dents, it will be threaded and can be adjusted by turning the tip clock-wise or counter clock-wise to shorten/lengthen it.

The booster output rod should come just short of touching the back of the MC primary piston (not actually touching), when the brake pedal is in the static position (pedal not being applied). There should be between .005"-.010" clearance/gap.

This procedure shows you how to measure and adjust the booster output rod for the MC being installed on the booster.

https://www.google.com/url?sa=t&rct=...OZYedkvaB_Y0cu

 

Great! Thanks again Steve!