Power brake conversion
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Junior User
Joined: Jul 1999
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Power brake conversion
Quick question. I'm in the midst of the power brake conversion on my '70 F-100. Do I need to change anything under the dash or will the brake booster with supplied push rod simply bolt right up to the dash and use the existing pedal? Unfortunately, I didn't get the chance to purchase an entire donor truck and I'm not entirely sure what I need under the dash? Thanks in advance for any replys. Joe
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Power brake conversion
Hi Joe and welcome to FTE! You shouldn't need to change anything under the dash but did you get the bracket that goes between the booster and firewall? There's also a plastic tube that the pushrod passes through. The intake manifold needs the vacuum tree with the big port. How far along are you into it?
Barry
Barry
Senior User
Joined: Dec 2001
Posts: 105
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Power brake conversion
I am doing this very job on my '68 tomorrow, and for insurance, I pulled the pedal assy. from the '67 I got the booster from at the junkyard.
I am under the impression that the brake pedal is slightly different to accomodate the rod on the booster. I will let you know if in fact you do need to change pedal assemblies. I am teeing off of the distributor advance. I will let you know the size and type of T that I will end up using.
Good luck with your project.
I am under the impression that the brake pedal is slightly different to accomodate the rod on the booster. I will let you know if in fact you do need to change pedal assemblies. I am teeing off of the distributor advance. I will let you know the size and type of T that I will end up using.
Good luck with your project.
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Power brake conversion
Joe, if your headed back to the yard you might as well pick up the pedal too. Another thing to get is the vacuum hose bracket that bolts to the firewall, this supports the hose between the engine and booster.
Say nice looking truck rtbstrd! Your right, the pedals are slightly different. The standard pedal will work but it might be a little low. There is a slight difference in the location of the hole that the rod bolts to. Some boosters have an adjustable rod that can compensate for this.
Stockman could explain this better but the '67 pedal is quite different than the '68 - '72 pedals. So is the power booster, it's smaller than the later models. Also the brake light switch is more like the passenger cars, mounted down where the rod attaches to the pedal. You'll have to cut and splice your harness to it. Don't tee off the dizzy, the booster can "suck" a lot of vacuum and needs a direct source.
Again, that is a nice looking truck!
Barry
Say nice looking truck rtbstrd! Your right, the pedals are slightly different. The standard pedal will work but it might be a little low. There is a slight difference in the location of the hole that the rod bolts to. Some boosters have an adjustable rod that can compensate for this.
Stockman could explain this better but the '67 pedal is quite different than the '68 - '72 pedals. So is the power booster, it's smaller than the later models. Also the brake light switch is more like the passenger cars, mounted down where the rod attaches to the pedal. You'll have to cut and splice your harness to it. Don't tee off the dizzy, the booster can "suck" a lot of vacuum and needs a direct source.
Again, that is a nice looking truck!
Barry
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Joined: Dec 2001
Posts: 105
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Power brake conversion
Barry,
I got advice from my parts guy ('69 Camper Special) to T from the DA vacuum fitting. It's the small one in front, there is a bigger fitting for the carb. Should I tee off of that one instead?
Another post in this forum (waaaay back) indicated that it's ok to t from the dist. vac.
What are you suggesting, that I drill and tap the intake for a separate fitting?
Thanks for the kind words about my F!
I got advice from my parts guy ('69 Camper Special) to T from the DA vacuum fitting. It's the small one in front, there is a bigger fitting for the carb. Should I tee off of that one instead?
Another post in this forum (waaaay back) indicated that it's ok to t from the dist. vac.
What are you suggesting, that I drill and tap the intake for a separate fitting?
Thanks for the kind words about my F!
Senior User
Joined: Nov 2001
Posts: 294
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From: Calgary Canada
Power brake conversion
I just finished convering my '72 to power brakes. All I did was buy a rebuilt master cylinder and vacuum booster. I bought a booster from the junk yard at first but it leaked but at least I got the booster-to-firewall brackets and there was a $80 core charge on the rebuilt booster so the $12 I spent on the junker was necessary. The booster rod bolted right up to the original pedal. All I had to do was adjust the brake light switch a little.
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Power brake conversion
Sometimes you can’t get enough adjustment on the brake light switch when the pedal is lower. A few posters had to make a spacer block when this happened, no big deal. I did this conversion when I first got my truck. I originally used the existing pedal but eventually ended up pulling a power pedal later. Sedric, out of curiosity, how much lower did your pedal go?
PH, I’m not that familiar with the vacuum hose routing on the 240 but the V8s used a special vacuum tree on the intake manifold with a big port just for the booster. The tree for non-power brakes only has the small ports. Personally I wouldn’t tee off the small vacuum lines because every time the brakes are applied the booster will “gulp” a large volume of vacuum. A small hose can’t supply the instant demand so it slowly bleeds it to the booster as fast as it can. When this is happening it robs vacuum from the other components that are in the same tee. This is kind of a backwards explanation, the booster is really bleeding air back into the manifold.
Man, I love the color of your truck!
Barry
PH, I’m not that familiar with the vacuum hose routing on the 240 but the V8s used a special vacuum tree on the intake manifold with a big port just for the booster. The tree for non-power brakes only has the small ports. Personally I wouldn’t tee off the small vacuum lines because every time the brakes are applied the booster will “gulp” a large volume of vacuum. A small hose can’t supply the instant demand so it slowly bleeds it to the booster as fast as it can. When this is happening it robs vacuum from the other components that are in the same tee. This is kind of a backwards explanation, the booster is really bleeding air back into the manifold.
Man, I love the color of your truck!
Barry
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Junior User
Joined: Jul 1999
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Power brake conversion
Wow, thanks for all the quick responses. I'm just getting started on the conversion. A buddy of mine had a later 70's frame(he used the majority of the body parts for one of his projects). I just took a sawzall to it and cut off the front half of the frame. Scored the P/S gear box, cooler, and everything else free. In the process of stripping the I-beams, spindles, prop. valve and all the rest of the greasy mess! I'm also doing the P/S conversion. Still need the shorter column and double groove pulleys. My intake already has a hole plugged off on back for the vacuum source for the booster. Sounds like I still need the bracket between the booster and firewall.
The pickup itself is a '70 F-100 Flareside w/ 302. I've posted on this site in the past, and have always gotten great advice!
The pickup itself is a '70 F-100 Flareside w/ 302. I've posted on this site in the past, and have always gotten great advice!
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Joe Kucinski
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
Power brake conversion
Ozzie, you got the easy parts, those parts that you don't have are the killers. That is why I always recommend that everyone buy his donor and get all the parts, and give the hulk to the crusher.
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John
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John
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In the cool still quiet of night, you can hear chevies rusting away.
Thread Starter
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Junior User
Joined: Jul 1999
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Power brake conversion
You're definitely right there, John. I'm in no hurry though. The PS and PB are a luxury. I've daily driven it to work the last three years the way she is and it doesn't bother me a bit. Unfortunately, the wife likes it too much and wants to be able to drive it herself some. Is that a good or bad thing??? Hhhhmmmm..... I readily admit though that it will be a pleasure to drive once the conversion is done. Thanks again guys. Joe
Lead Driver
Joined: Feb 2000
Posts: 5,374
Likes: 46
From: Palm Bay, Florida
Power brake conversion
Is your truck a I6? thats what I'm getting from this.
If so I recently went through the same problem with a vacuum source with mine:
My intake had only 1 large vacuum port just under where the carb mounts, so I got a brass threaded nipple (short) and a "T" then a barbbed 3/8" fitting for my brake booster to hook to, then used a factory vacuum tree to hook up my PCV valve, & trans. modulator line to. Your distributor vacuum needs to come from the small vacuum port on the carb itself.
My suggestion is to get the booster to firewall bracket, and pedal from the same truck that you got your booster from & use it all in your truck for a trouble free installation.
If so I recently went through the same problem with a vacuum source with mine:
My intake had only 1 large vacuum port just under where the carb mounts, so I got a brass threaded nipple (short) and a "T" then a barbbed 3/8" fitting for my brake booster to hook to, then used a factory vacuum tree to hook up my PCV valve, & trans. modulator line to. Your distributor vacuum needs to come from the small vacuum port on the carb itself.
My suggestion is to get the booster to firewall bracket, and pedal from the same truck that you got your booster from & use it all in your truck for a trouble free installation.
