Hey all, I am waiting on brake parts to arrive from Brothers to complete my front disc brake conversion. My question is this, is it necessary to use a booster, or will the original master cylinder be adequate? If a booster is needed, what are my options for installation? Brothers says the power brake booster/master cylinder they sell will not work on trucks with a manual transmission. Why wouldn't this work? Is it possible to mount a power setup under the hood like on later vehicles?
Your stock master cylinder COULD work.......but it is single chamber and not as safe as a dual circuit type used since '67. As for the effort required, and the volume required for the calipers......not so sure. You could use a firewall mounted master/booster and keep the floor mounted clutch pedal, but would that suit you? On the other hand, with some fabrication you could use an underfloor master/booster and keep the pedals alike. It would probably require mounting the master/booster rearward somewhat and building a suitable (strong) bracket and a longer pushrod. Also, there are some GM electric powerbrake systems that can be retrofitted and I think they are a bit more compact than the typical vacuum booster. Offroad guys like those because if the engine dies they still have power grakes. Ray
i'd give it a try as it is, but there is one thing you have to change: drum brakes have a 10psi checkvalve so they can be pumped up. disk brakes do not use a checkvalve as they have no retract springs. If pedal effort is too high, you must use a smaller bore master cylinder and that means more pedal travel....or a brake booster, boosters usually don't require much pedal travel. There are remote boosters which free up the location. The disk brake may require more fluid which may then take up all of your pedal travel. And there is a rear to front balance of your brakes which must be controlled with a proportioning valve. On all drum systems, the balance is controlled with brake shoe width.
I would add that a proportioning valve MAY be needed.....they are not ALWAYS needed. And, if the master cylinder is lower than the calipers, a 2# residual pressure valve should be installed in the disc brake line. Ray
I think it would be a good idea to change out the MC but I would not use a booster. I installed one on my '40 pickup and feel I would be happier without it. It is is too responsive and I prefer to feel the pedal. A proportioning valve and residual valves would also be a good idea. Just what has worked for me.
If that setup comes with it's own pedal that is why they say it won't work with a standard trans as they don't have a provision on their pedal bracket to mount the clutch bracket. If it is running the trucks original pedals you could as Hnstray said in the middle of post 2 build or modify the bracket to move the booster and cylinder to the rear a bit. You would have to build a new rod from the pedal to the booster though. And yes you could mount the booster and master cylinder on the firewall but to me that is a last resort unless it just won't fit under the floor as they are a big ugly zit hanging on the firewall and screw up the otherwise clean engine compartment.
The power booster I have (ECI I think) uses the stock pedal assembly. I had it installed in 20 minutes. mounted in place of the stock master cylinder and drill 2 holes in the frame rail
I've only done one DB conversion.. 64 F-100. I used a newer ford booster and MC, that matched to the size of wheel cylinders and calipers I was using (single piston calipers, same cylinder bore as car I picked master from etc...) it worked great. pedal felt the same as any modern car. I have driven rods with DB conversions where the pedal goes down over half way to slow the beast. that;s okay, but I like to feel secure when trying to stop thousands of pounds of car I love.
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