Drum/Drum Power Brake Conversion Help

[LSUMurse]

I've read a ton of posts on the forums and gained much insight, however I can't find a definitive answer to my questions.

I am looking to add a booster to the brakes to make the truck a little easier to drive for the little woman. I currently have drum/drum and don't (at this time) wish to change to disc. I realize I will need a booster, bracket to the firewall, the vacuum line, and the rod to the pedal.

My question is: Do I have to farm these parts off a pre-71 truck? Can I use the setup off of a mid to late 70's truck and just use my stock master cylinder, etc? I also have the stock 2-barrell carb (on a 307), is there a port to connect the vacuum line to?

Thanks in advance,
-Stephen

[hugger6933]

Well Stephen I will for the sake of helping on your truck deal set aside the whole Razorback / Tiger thing. Come now I had to take a shot, you have LSU right in your screen name. All kidding aside I am not near as rabid as most folks get. Now back to real important stuff the truck. You can use a later booster but you will need to make sure of what is needed to change it over to the square body style, and I am thinking that is the braket off of the 67-72 type booster. So if going to the trouble to find one to get the bracket off of to put on the later type booster why not just put it on the truck? The correct booster willhave the push rod attached to it if I remember, so to change it over you will need to remove the master cylinder [but not remove it from the truck, no need to break the line open] and pull it forward. Next there will be two more bolts holding the push rod plate to the firewall , remove them and the inside the truck remove the brake switch and the push rod. Install the booster then reverse the rest from the tear down. It is as about striaght forward as it can be. The carb question does not matter as the port that you will get your vaccum soruce from is the plug on the intake manifold, behind the carb. Now some say that the pedel hole needs to be droped down and redrilled but I can't speak to this cause I just don't know about that maybe some one else will help you on that, I do know the booster will indeed work in that hole it will be a little sensitive until you get use to it according to the post where the man had done that swap to his truck. Jim

[LSUMurse]

Thanks for the reply (even if it was from a Razorbacks fan ).

The reason I was asking is because my pickins are pretty slim down here. I am going to do a junkyard sweep today. It sounds like the most important thing is the bracket. I may just buy the one Capt Fab is reported to have.

Thanks again for the (only) reply. Here's to a better season for y'all next season, but not too good, one loss to LSU will be fine.

[j ripper]

This is a simple straight forward conversion. I would put a wanted add on the parts board or just keep a look out on there for one. I think I paid 100 bucks for a complete unit from a guy here in the bay area. I use the port on the manifold behind the carb for vacuum.
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[Legolas894]

I'm thinking about doing the same thing. I've got drum/drum also on my '67. ROCK AUTO has a complete master cylinder + brake booster for $125. That sounds good. The booster alone is $82 so why not change the whole thing. They have a check valve as well so I imagine you need that too. Anyone done this? Any other parts needed?

[PanelDeland]

You have to have the rod and bracket from a 67-72 to do it.The rod length is different from PB to manual and the bracket is required to make it a bolt in.You will need to adjust th brake line since the MC will be several inches further out from the firewall.Alength of hose and fitting for vaccuum and some brake fluid.If you swap MC you'll also need a helpre to bleed the brakes.

[Lattimer]

Originally Posted by PanelDeland

You have to have the rod and bracket from a 67-72 to do it.The rod length is different from PB to manual and the bracket is required to make it a bolt in.You will need to adjust th brake line since the MC will be several inches further out from the firewall.Alength of hose and fitting for vaccuum and some brake fluid.If you swap MC you'll also need a helpre to bleed the brakes.

I just did this this week. Had a junkyard master cylinder assy. with booster and brackets, but only the brackets and rod were any good. Got a reman booster and put it behind my existing master cylinder.

Hardest part of the whole thing was adjusting the brake light switch since the pedal height is now a touch different.

[hugger6933]

There is a post in the FAQ section and someone has done this and did the write up on it. I will probably not use the 67-71 type booster I have when I started out gathering parts for these truck once I started buying them. On the 70 Chevy I planned to do this to I will probably mount the later type booster flush up to the firwall similar to the later model trucks so that it does'nt stick out so far. That does not appeal to me. I have that luxury on mine that LSU does not because I am not working on my daily driver and that puts himas it would anyone behind the 8 ball being he needs his truck to roll not take up a shop bay. Now back to what I started out to say the poster the did this swap and the write up, said he did not bleed his brakes because he did not break any brake lines loose. He moved the M/C out of the way then when the time came he bolted it back up to the booster, that is what I was trying to get across in my post at first that being that way it should help in being that much faster getting it back on the road. my plan to do that to mine has now changed as Iwill go different direction as I will be taking mine down to frame rails and starting up from scratch, not just adding power brakes and steering and a 5 speed and 4 barrel and a HEI as I first had thought. Jim

[Legolas894]

Great-thanks for the helpful replies. I guess another question is "Is it worth doing?". I've got manual steering and a 4-speed floor shift. I never thought putting the brakes on was a chore and I always put the extra braking distance down to 4 wheel drums. The issue I have is that the M/C brake system switch doesn't work (it didn't trigger the brake light when I had a brake line broken on my front wheel. I drove around for a few days without front brakes. It seemed to get worse and when I popped the lid off the M/C, one of the reservoirs was empty! I was thinking of switching out the old stuff for new anyways but if I should go to power at the same time, it isn't much more. Any comments would be great.
Thanks