proportioning valve question
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New User
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From: Far Northwest Oregon,
proportioning valve question
Good morning, I have a question about the flow proportioning valve on my 67 f250 4x4. I just put the power break can and the master cylinder out of a 73 f250 2wd on my truck last night. Do I have to change the flow proportioning valve also? The one on the 67 is a brass block about 1/3 the size of the one on the 73.
Postmaster
Joined: Apr 2002
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From: Coal country
Old F250: I assume you also upgraded to front disc brakes as well? If you still have drum brakes in the front, then you need to get the proper master cylinder (M/C).
The '73 2wd M/C is (most likely) for front disc brakes, and you have to use either a M/C for drum/drum brakes, or change out your fronts to discs.
The disc/drum M/C is different internally, to work with disc brakes.
If you do not use both the correct M/C and the correct proportioning valve, you will be in for some nasty surprises.
You should be able to re-use your old M/C, or get one for a '67 with power brakes.
The '73 2wd M/C is (most likely) for front disc brakes, and you have to use either a M/C for drum/drum brakes, or change out your fronts to discs.
The disc/drum M/C is different internally, to work with disc brakes.
If you do not use both the correct M/C and the correct proportioning valve, you will be in for some nasty surprises.
You should be able to re-use your old M/C, or get one for a '67 with power brakes.
Postmaster
Joined: Apr 2002
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From: Coal country
If the donor truck has front drums, you are good to go!
However, if it is a '73, then it will have front disc brakes.
There is the possibility it is really a '72 with drum brakes which was erroneously titled as a '73. (This often happened at the end of the model year, when left-overs were sold in September.)
1973 was the first year that front discs were mandated by federal law.
Now, there may have been an exception for "heavy duty" trucks, and the '73 F-250 may have qualified as a heavy duty truck, and therefore may have front drums.
However, if it is a '73, then it will have front disc brakes.
There is the possibility it is really a '72 with drum brakes which was erroneously titled as a '73. (This often happened at the end of the model year, when left-overs were sold in September.)
1973 was the first year that front discs were mandated by federal law.
Now, there may have been an exception for "heavy duty" trucks, and the '73 F-250 may have qualified as a heavy duty truck, and therefore may have front drums.
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New User
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From: Far Northwest Oregon,
I jist got back from looking at the doner truck and you are right , It does have disk brakes. So I went and bought a master cylinder that works for drum brakes - $18 not to bad. I am still worried about the proportioning valve. I am going to put what I have together and see what happens. Thank you for the help.
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Postmaster
Joined: Apr 2002
Posts: 3,613
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From: Coal country
Since your old proportioning valve is drum/drum, I am not sure why you need a newer proportioning valve if all you added or changed was the power booster?
Maybe someone else can weigh in on this one?
It doesn't seem to me that you need the newer proportioning valve.
Maybe someone else can weigh in on this one?
It doesn't seem to me that you need the newer proportioning valve.
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New User
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From: Far Northwest Oregon,
I put it all together and I have a hard pedel. No free pedel. It is pushed up so hard I can not push it down far enough to make the brake lights come on. It's like the E-brake is on all 4 wheels. Any ideas?
Postmaster
Joined: Apr 2002
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From: Coal country
It sounds like the push rod from the pedal to the booster is incorrect.
Those of us who do this conversion (including the discs changeover) on the '65 and '66 trucks run into this problem. I can tell you that the '73 and later rod is too long, which will push the pedal up too high.
My initial measurements of my son's '72 indicated the same issue, so you may need to shorten the rod.
Others have also indicated that a new hole can be drilled in the brake pedal.
I have the booster from a '76 F-150, and it has a flat bar instead of a rod. When I finish the installation, I will need to drill a new hole in the bar/rod to keep the pedal in the right place.
Try researching the '61 - '66 forum for more details.
Be sure to use only information from '65 and '66 trucks, though as the '64 and earlier ones are a completely different animal under the hood and frame.
Good luck!
Those of us who do this conversion (including the discs changeover) on the '65 and '66 trucks run into this problem. I can tell you that the '73 and later rod is too long, which will push the pedal up too high.
My initial measurements of my son's '72 indicated the same issue, so you may need to shorten the rod.
Others have also indicated that a new hole can be drilled in the brake pedal.
I have the booster from a '76 F-150, and it has a flat bar instead of a rod. When I finish the installation, I will need to drill a new hole in the bar/rod to keep the pedal in the right place.
Try researching the '61 - '66 forum for more details.
Be sure to use only information from '65 and '66 trucks, though as the '64 and earlier ones are a completely different animal under the hood and frame.
Good luck!
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New User
Joined: Dec 2003
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From: Far Northwest Oregon,
Mine has a flat bar instead of a rod also. So you are saying that I need to drill a new hole in the brake pedal arm, (up or down)? This was a problem before I changed it over. The hard pedal thing. The rod coming out of the can into the master cylinder has an adjustment scrwe end on it and I have screwed it all the way in and it still is not short enough so I guess the new hole thing is my next step.
Thanks, Rick
Thanks, Rick
Post Fiend
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From: Brea CA
Originally Posted by banjopicker66
The disc/drum M/C is different internally, to work with disc brakes.
Last edited by BB; Sep 27, 2004 at 04:06 PM.