Power brake conversion
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Cargo Master
Joined: Jan 2004
Posts: 2,512
Likes: 8
From: Cook Forest and Irwin PA
Power brake conversion
I have a 1981 F100 that has manual front disk, rear drum brakes.
I have a 1990 booster and M/C that I wish to install.
From what I have seen underneath the dash/hood is that the 4 bolt mounting is the same and there is the same cast bracket that strengthens the firewall to the steering column mounts.
the rear brakes on the trucks are exactly the same.
the front calipers are different (one was a 4x4, other was a 2wd)
It appears that BOO is the same on both trucks and so is the pedal fulcrum length.
Has anyone ever done this conversion? Both the manual M/C and the power one appear to have the same fittings and both go into a proportioning valve.
Oddlly, since the rear end on the 81 is from the 90, I retained the DSS - I guess I could technically transplant the RABS as well? (but I digress)
I note that for 1981 there are 2 2wd calipers - w/o PB and w/PB.
and apparently if you change calipers, you also need to change kingpin bushings. Lets assume this is a future project...will the stock calipers explode or something if boosted? (having not done any measuring I am assuming the the manual calipers have more surface area to provide stopping power)
Ideas? suggestions?
(I also note the 80-82 2wd trucks had a different front 'Twin I beam' than the later models, but it is located the same. I guess I *could* yank the front end off a 2wd 87-newer and be done with it...)
I have a 1990 booster and M/C that I wish to install.
From what I have seen underneath the dash/hood is that the 4 bolt mounting is the same and there is the same cast bracket that strengthens the firewall to the steering column mounts.
the rear brakes on the trucks are exactly the same.
the front calipers are different (one was a 4x4, other was a 2wd)
It appears that BOO is the same on both trucks and so is the pedal fulcrum length.
Has anyone ever done this conversion? Both the manual M/C and the power one appear to have the same fittings and both go into a proportioning valve.
Oddlly, since the rear end on the 81 is from the 90, I retained the DSS - I guess I could technically transplant the RABS as well? (but I digress)
I note that for 1981 there are 2 2wd calipers - w/o PB and w/PB.
and apparently if you change calipers, you also need to change kingpin bushings. Lets assume this is a future project...will the stock calipers explode or something if boosted? (having not done any measuring I am assuming the the manual calipers have more surface area to provide stopping power)
Ideas? suggestions?
(I also note the 80-82 2wd trucks had a different front 'Twin I beam' than the later models, but it is located the same. I guess I *could* yank the front end off a 2wd 87-newer and be done with it...)
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
> I have a 1981 F100 that has manual front disk, rear drum brakes.
I thought the only thing offered in 1981 was power front discs, never heard of manual discs that year.
> Has anyone ever done this conversion?
Not exactly how you are doing it. What I usually do is go buy a master/booster combo for a disc brake F-350 of that year and swap it right in. From the 70s to at least the 90s, most of the brake stuff swaps right in. Except for vans.
> both go into a proportioning valve.
Equalizer valve - it prevents total brake loss if one circuit fails.
> since the rear end on the 81 is from the 90, I retained the DSS - I guess I could technically transplant the RABS as well? (but I digress)
Yes, that year it still should be an autonomous system (mid 80s-1990) and not tied to the main CPU. Plus, your 1981 does not have a computer. So, that year range is a good swap.
As for the calipers, I think it is what you said, the piston has a wider surface area and that is the difference.
I thought the only thing offered in 1981 was power front discs, never heard of manual discs that year.
> Has anyone ever done this conversion?
Not exactly how you are doing it. What I usually do is go buy a master/booster combo for a disc brake F-350 of that year and swap it right in. From the 70s to at least the 90s, most of the brake stuff swaps right in. Except for vans.
> both go into a proportioning valve.
Equalizer valve - it prevents total brake loss if one circuit fails.
> since the rear end on the 81 is from the 90, I retained the DSS - I guess I could technically transplant the RABS as well? (but I digress)
Yes, that year it still should be an autonomous system (mid 80s-1990) and not tied to the main CPU. Plus, your 1981 does not have a computer. So, that year range is a good swap.
As for the calipers, I think it is what you said, the piston has a wider surface area and that is the difference.
