how do I determine the right brake rod length

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bunchoftrucks
Posts: 123
Joined: November 12, 2011, 4:52 pm
Location: Colorado Springs,Colorado

how do I determine the right brake rod length

Post by bunchoftrucks »

I'm trying to get some solid information on setting my brake push rod to the right length and can't seem to get any good answers.I swapped a 79 F-150 4x front end into my 66 F-100 4x to get the disc brake front end. I used a 69 Mustang M/C and the 79 prop valve. I just don't feel that I'm getting the braking power I should be and need some direction.
64 F-250 4x4 391 FT
66 F-100 4x4 352 FE
64 shortie 302/AOD
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totten
Posts: 284
Joined: January 1, 2012, 8:05 pm
Location: Erlanger,ky
United States of America

Re: how do I determine the right brake rod length

Post by totten »

Maybe your petal is too low. did you set the petal at same height? I had to cut the m/c push rod to match stock rod. You didn"t say if power booster was added. I used 68 mustang m/c and split front and rear brake lines to master cylinder. I have no power booster and stock 4-wheel drum brakes. Works good.
1966 f-100 ranger,red and white,240,cruiseomatic,3.00 gear,a/c.
bunchoftrucks
Posts: 123
Joined: November 12, 2011, 4:52 pm
Location: Colorado Springs,Colorado

Re: how do I determine the right brake rod length

Post by bunchoftrucks »

I didn't think to measure it before I did the swap so I don't know the correct pedal height. The m/c that I bought didn't come with a new push rod and the stock unit wasn't long enough at all. I didn't use a power booster, used a 68 disc/drum m/c and split the lines front and rear. It doesn't feel like it has enough without alot of leg, I checked the pedal ratio and found it to be low.
64 F-250 4x4 391 FT
66 F-100 4x4 352 FE
64 shortie 302/AOD
ICEMAN6166
Posts: 11470
Joined: July 11, 2006, 11:28 am
Location: Dove Creek, Co. elevation 6842
Poland

Re: how do I determine the right brake rod length

Post by ICEMAN6166 »

why did you not use the m/c for a 79 f150 4x4?

i have done the dual m/c conversion a few times with 4 wheel drum brakes and used m/c from 72 f250 4x4 with drum/drum, shortened rod from 72 f250 4x4 a hair under 1" and no problems.

maybe the m/c for the mustang does not have a big enough bore to push the fluid needed for the 79 4x4s disc brakes.
1966 F250 4x4
1964 Rambler Ambassador 990
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Cam Milam
Lesley Ferguson
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totten
Posts: 284
Joined: January 1, 2012, 8:05 pm
Location: Erlanger,ky
United States of America

Re: how do I determine the right brake rod length

Post by totten »

I have to use good leg pressure with mine. Might need power booster off of 79. The 68 mustang m/c bore is 1",should be large enough too push disc brakes on front. I would set petal height first for ratio. The push rod that i shortened about 1" like ICEMAN said. It was still longer than the stock rod. Or use 79 m/c with booster. Tony :2cents:
1966 f-100 ranger,red and white,240,cruiseomatic,3.00 gear,a/c.
William-in-St George
Posts: 579
Joined: December 31, 2009, 5:26 pm
Location: Saint George Utah

Re: how do I determine the right brake rod length

Post by William-in-St George »

BTDT! I sawed the rods, drilled the pedal and generally screwed around with this issue for a long time. The right answer is to simply add 4 one inch spacers between the fire wall and step linkage. This deal is 100 % all Ford stuff except for the 4 spacers. I use the brake pedal from the donor truck (wide pedal), the brake support from the Slick, a gasket/firewall seal from Mustang, mechanical step bracket from the Donor (Ford), the booster (usually core this), and the master cylinder of your choice. I like the lines to exit the MC on the left and use a 1 1/4 inch diameter piston. If you have a hard pedal it is likley that you are using a MC with too large piston. If you peel your face off the windshield everytime you use the brakes likley you have a too small MC piston. Really all this is easy and all Junk Yard parts too boot!
William-in-St. George
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