Hello,

I have a 1982 F100 with manual brakes. I would like to convert to power brakes. From what I can tell from various parts suppliers, it looks like I should be able to buy the power booster and mount it on the firewall, mount the master cylinder on the booster, make longer steel lines to the master cylinder, and run the vacuum line to the manifold. Is it really that simple? Is the power brake booster a "shoe-in", or is there some difference in the brake pedal as well? It looks like my fire wall has the four holes for mounting the booster - it looks like it has an adapter plate that mounts in these four holes and has two studs that the master cylinder is mounted to.

Parts suppliers list different master cylinders for power brake versus manual brakes. However, they appear to be physically identical. Also, both show as having a 1" bore. Is there any significant difference between the two? My master cylinder is old, so I have not problem with buying a new power brake master cylinder, I am just wondering what the difference may be, and how that might affect my conversion.

Thanks,
Jim

 

It is not a hard conversion, you hit most of what you need to do in your post. You will need the power brake pushrod (pedal to booster) as well the bracket for the brake light switch as the pedal will be a bit lower in relation to its old position. Sometimes there is enough adjustment though to make up for the difference without changing the bracket. The pedal is a bit wider as well, at least in the case of the automatics. Your choice on if you want to change the pedal if you have a automatic. Certainly there were manual transmission trucks with power brakes made

If the parts book shows a different cyclinder, than ther is probably a important difference. Unfortuantly I have never had a manual braked 80-86 truck that I have worked on in the master cylinder replacement department, so I can't tell you exactly what the difference is. It could be though that the actuating rod is the iffernce,a s it may be attatched to the power brake cylinder directly, and in the case of manual brakes it is attatched to the pedal -- Power brake setups do require a rod between not only the master cylinder / booster, but also between the booster / pedal.

You are lucky in that most of these trucks were equipped with power brakes, and there are lots of parts available used at the wreckers / parts recyclers.

I hope this helps, David

 

There may be a difference in the brake pedal itself. I was looking at converting my mustang to power brakes, and I noticed the pedal for power brakes has a different pivot point to take advantage of the boosters help. The non power pedal is setup to give you more leverage on the MC. As I said though this is on my mustang, may be different for trucks, but something worth looking into.

You should be able to get that cheap though, I just got the entire pedal bracket assembly so I could convert my truck to a manual, and it only cost me $25 from the junkyard. It was nearly $200 from LMC, and that didn't include pedals.

 

Thanks for the information. I was just looking at the AutoZone web site, and it looks like I can get a rebuilt power brake booster with the power brake master cylinder already attached for $131. It looks like the booster includes the linkage to the pedal. I would have to order that, but they normally stock the booster and MS separately, and it looks like the booster includes the linkage on both sides. The price for the separate pieces is similar, so I will probably go that route. My truck has a manual trans, so the pedal is no issue as long as the linkage fits. The remaining issue that you pointed out is the brake light switch. I had not thought of that. I will check into that today. However, that can't be a show stopper. If I can get the booster, MS, lines, etc. installed and working, a brake light switch will be no problem even if I have to fabricate something.

Thanks again,
Jim

 

Sounds like a good find and a good plan. David

 

i dont know if ytou already mentioned this and sorry if you did, but did you locate a source for the vacuum for the power assist?

 

Well, to be truthful, no. I don't know where the factory connected the vacuum line, but if it went to the manifold directly, there is sure to be a plugged hole there. They would not have gone to the expense/trouble to make different intakes for manual vs power brakes. I don't think it will be a problem to find vacuum somewhere.

Thanks.
Jim

 

Update, for anyone who is interested (maybe you are considering this change for your truck?)

I bought the power brake booster and the power brake master cylinder. Removing the manual brake MS and installing the power brake booster was a snap. I did it myself in about 30 minutes. It would have been a 15 minute job if I had a helper to hold a wrench under the hood while I turned the rachet under the dash.

Next I installed the power brake MS. This was a 2 minute job. It took longer to tear open the plastic bag that the MS came in than it did to install it.

The old steel brake lines to the old MS where in good shape and were more than long enough to reach the new MS location. The front line (which goes to the rear brakes) went on without any problem. The rear line (which goes to the front brakes) was a different story. The nut on the line was the wrong size. The lines are -3 size, or 3/16" diameter, which normally takes a standard 3/8" - 24 brake line nut. However, there are two other "standard" brake line nuts for -3 lines which are called "Master cylinder nuts". These come in 7/16"-24 and 1/2"-20 thread. The rear steel line for the manual brake MS uses the 7/16" - 24 nut. The rear steel line for the power brake MS uses the 1/2" - 20 nut. I am going to have to cut the flare off of the one line and replace the nut are reflare the line.

Regarding the master cylinders, they appear to be physically identical (at least, the casting seems to be identical). Both also have 1" pistons. The differences that I have found so far are the different size for the one brake line, and the manual brake MS has the linkage attached to the piston, so I can't just put the old MS back on. There might be a way to remove the linkage and use the old MS with the power booster, but I don't want to put a 25 year old MS onto my new power booster.

Incidently, looking at the LMC Truck catalog, they have a pre-bend stainless steel brake line kit, but they make no distinction between manaul and power brakes for my truck. Makes me wonder which nut the rear MS line comes with?

Ford did some crazy stuff with Master Cylinder nuts on my truck. I replaced the steel lines on my rear axle. When I got to the brass "Tee" where the two steel lines connect to the flex line, I discovered that one side of the Tee used a standard 3/8" - 24 brake line nut, but the other side used a 7/16" - 24 MS nut. I had to cut the flare off of the new line and the old line, swap the nut, then reflare the new line. You would think that they were worried that I might put the Tee in backwards!

Oh well, it all looked so easy, I knew there would be some little hitch somewhere. If you are thinking about making this conversion, check the size of the threads on line connections on your new MS to make sure you have the right size brake line nut before you start. My truck is dead in the driveway until I can find the larger nut and install it. I have found a source for them on the internet, but so far I have not found any parts store that carries them. Looks like I will have order the new nut and wait for delivery.

Jim

 

You know most auto parts stores(at least around here) carry brake line adapters. I installed a booster/MC combo from a 90' F-250 in my truck, and both brake lines were different sizes. What I did was take both MC's down to the store, found a replacement line that fit my old MC so I new what the size was and then looked through the drawers of adapters for one that would fit between the line I had found and the new MC.

 

you hit it right on the nose with the adapters thats what a couple of my trucks have hed on them.