brake conversion questions
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Senior User
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brake conversion questions
Howdy,
Preliminary info: my truck is a '72 f100...donor truck is a '74 f100
Two questions:
1. Do I need to exchange my original brake booster for the one from the '74?
2. The proportioning valve from the '74 is rusted out...do I need to find another '74 valve or can I use one from a later model f100/150? The master cylinders changed between '74 and '75 and also between '76 and '77.
Preliminary info: my truck is a '72 f100...donor truck is a '74 f100
Two questions:
1. Do I need to exchange my original brake booster for the one from the '74?
2. The proportioning valve from the '74 is rusted out...do I need to find another '74 valve or can I use one from a later model f100/150? The master cylinders changed between '74 and '75 and also between '76 and '77.
Fleet Mechanic
Joined: Jul 2002
Posts: 1,297
Likes: 34
From: S/W Virginia
Don't know about the brake booster, but any proportioning valve will work, as long as its off of a truck. All it does is limit the amount of pressure applied to the rear to keep them from locking up.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Originally Posted by tonpartain
Howdy, Preliminary info: my truck is a '72 f100...donor truck is a '74 f100
Two questions:
1. Do I need to exchange my original brake booster for the one from the '74?
2. The proportioning valve from the '74 is rusted out...do I need to find another '74 valve or can I use one from a later model f100/150? The master cylinders changed between '74 and '75 and also between '76 and '77.
Two questions:
1. Do I need to exchange my original brake booster for the one from the '74?
2. The proportioning valve from the '74 is rusted out...do I need to find another '74 valve or can I use one from a later model f100/150? The master cylinders changed between '74 and '75 and also between '76 and '77.
John
Postmaster
Joined: Apr 2002
Posts: 3,613
Likes: 6
From: Coal country
You didn't say if your '72 has disc or drum front brakes - I assume it has drums.
You MUST change the proportioning valve to a disc brake type if you change from drums to disc.
It is called a proportioning valve for a reason: it delivers more braking force to the front by proportioning it out, to give you more effective braking.
They can be had a boneyards easily enough.
You MUST change the proportioning valve to a disc brake type if you change from drums to disc.
It is called a proportioning valve for a reason: it delivers more braking force to the front by proportioning it out, to give you more effective braking.
They can be had a boneyards easily enough.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Originally Posted by idealtrucks
If you can't find a proportioning valve, just use your original distribution block and put an adjustable valve on the line going to the rear.
John
Fleet Mechanic
Joined: Jul 2002
Posts: 1,297
Likes: 34
From: S/W Virginia
All a proportioning valve does is send more fluid to the front and less to the back. It keeps the back drums from locking before the front discs do. If you just buy an inline aftermarket adjustable prop. valve and put in in the line to the rear, you are essentially doing the same thing, but are simply able to adjust it. Race applications use this all the time to get the bias that they want. 
