Weak brakes
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Weak brakes
Hey Guys
I just finished my 2 year resto on my 79 f150 4 wheel drive.
Took it for it's first test drive and the brakes are no better then manual brakes.
I am running a 92 460 efi coupled to a zf 5 speed. I retained the hydraulic clutch and only had enough room for an 8 inch booster due to the proxcimity of the clutch master. Anyone else running this setup and might have a solution?
Thanks
I just finished my 2 year resto on my 79 f150 4 wheel drive.
Took it for it's first test drive and the brakes are no better then manual brakes.
I am running a 92 460 efi coupled to a zf 5 speed. I retained the hydraulic clutch and only had enough room for an 8 inch booster due to the proxcimity of the clutch master. Anyone else running this setup and might have a solution?
Thanks
Laughing Gas
Joined: Jun 2010
Posts: 1,056
Likes: 10
From: Indiana, PA
x2 on the hydro boost.
I always liked it driving around Superdutys and am in the middle of the swap onto my 76 Ford.
Here is a great resource for doing the swap.
Welcome to Hydratech Braking Systems :: High Performance Hydraulic Brake Assist Systems
They can sell you a swap "kit" for your truck, though you can do it all yourself with a little bit of fabrication for a lot cheaper.
I always liked it driving around Superdutys and am in the middle of the swap onto my 76 Ford.
Here is a great resource for doing the swap.
Welcome to Hydratech Braking Systems :: High Performance Hydraulic Brake Assist Systems
They can sell you a swap "kit" for your truck, though you can do it all yourself with a little bit of fabrication for a lot cheaper.
Postmaster
Joined: Nov 2011
Posts: 2,553
Likes: 10
An 8" single booster is not near enough. An 8" double booster would likely work OK. Agree hydroboost would work best.
I run the original big (10 or 11"?) booster on my '78 and brakes are great... with near stock size tires. With taller tires, I understand the stock system gets marginal.
I run the original big (10 or 11"?) booster on my '78 and brakes are great... with near stock size tires. With taller tires, I understand the stock system gets marginal.
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New User
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Thanks for the replys,I do have a double diaphragm booster however there is this weird lever that doubles the through before the booster that I left intact, not sure how to eliminate that. Perhaps that could be part of the problem.
Postmaster
Joined: Nov 2011
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There are lots of linkage variations on these trucks. Did you switch it from manual to power brakes with the resto? Hopefully you got a complete PB linkage and pedal setup from a donor truck.
In general, increasing the "throw" is common with PB since the booster is applying a lot of the force.
As a suggestion for a couple of diagnostics, try pulling and plugging the vacuum feed to the PB and drive it around the lot. Are the brakes worse or the same? This will tell you if the vacuum booster is doing anything.
It also would not hurt to put a vacuum gauge on the vacuum feed and make sure you are getting full vacuum.
The other area to check is MC pushrod length. If (or since) you are using a non stock combo, the pushrod from the booster to MC may be the wrong length. Usually they are adjustable. Too short would give you weak brakes. Too long would make the brakes drag. I don't have a step by step to check and it takes a special tool. Trial and error may work.
In general, increasing the "throw" is common with PB since the booster is applying a lot of the force.
As a suggestion for a couple of diagnostics, try pulling and plugging the vacuum feed to the PB and drive it around the lot. Are the brakes worse or the same? This will tell you if the vacuum booster is doing anything.
It also would not hurt to put a vacuum gauge on the vacuum feed and make sure you are getting full vacuum.
The other area to check is MC pushrod length. If (or since) you are using a non stock combo, the pushrod from the booster to MC may be the wrong length. Usually they are adjustable. Too short would give you weak brakes. Too long would make the brakes drag. I don't have a step by step to check and it takes a special tool. Trial and error may work.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
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Regular User
Joined: Sep 2014
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From: Bathurst, New Brunswick
This may seem like an overly simple question but, are the rear brake shoes adjusted out? If they aren't, the pedal feel isn't going to be good and the brakes aren't going to respond like they should.
Link to a simple procedure for adjusting the booster-to-MC output rod length.
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Link to a simple procedure for adjusting the booster-to-MC output rod length.
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More Turbo
Joined: Dec 2013
Posts: 647
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From: SOUTHBURY CT
i was having issues on my 79 f250 till i learned that little rod needed to be turned out u dont need special tools just a wrench to hold the rod and a wrench to turn the adjuster, it should stick out about 15/16 of a inch.
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