Power brake booster & master cylinder for drum brakes

[Seattle66]

I have a question about the master cylinder setup options for stock drum brakes front and rear.

I bought the power brake booster kit from TBP for Drum brake lines (part # 7040). It came with a typical uneven dual chamber master cylinder, which makes me believe either I bought the wrong kit or it doesn't matter if the master cylinder chambers are uneven. When installing it, I noticed that the previous owner of my Bronco had swapped out the h block for a proportioning valve and a uneven dual chamber master cylinder.

My question is:

--Can I run a uneven dual chamber master cylinder and proportioning valve with front and rear drum brakes? Won't that cause uneven braking between the front the rear? The proportioning valve on my Bronco is not adjustable. I think it might be the proportioning valve that Wild Horses sells for 4 wheel drum brakes or 4 wheel disc brakes (part 3037): http://www.wildhorses4x4.com/product/Proportioning_metering_valve.


I eventually want to swap the Dana 30 for a 44 with disc brakes, so the new master cylinder I have will work with that, but in the mean time I need it to work with my drums or need to buy a different even chambered master cylinder.

 

[Apogee]

Most drum/drum systems don't run proportioning valves as they're not needed. The wheel cylinders should be sized such that you get the proper front/rear brake bias given the application. In disc/drum applications, proportioning is typically desired since the rear drums create a non-linear level of brake torque relative to pressure due to the self-energizing servo-action of the shoes inside the drum the harder they're applied combined with the weight transfer to the front tires.

As for the reservoir size in the MC, those don't impact hydraulic function at all, they're simply a reservoir for the brake fluid such that the MC doesn't run dry under braking, at angles, etc, while compensating for pad wear in a disc application. That's why the reservoirs tend to be larger for disc applications versus drum, it has nothing to do with functionality.

 

[Timmy390]

I can't help with everythign but can help with some.

My stock 74 MC is "uneven" dual chambered for drum/drum brakes. I ran the stock style power booster and drum/drum brakes for about 10 years without issues however I was running the stock H-block. The only issue I had was keeping the fronts adjusted or it would pull during hard braking. It wasn't a real issue per say, I just had to adjust them once in a while.

I would think if it worked with the old MC and P-valve, it will work with the new M/C. it's my understanding (I'm sure someone will correct me if I'm off base) the dual MC works the same as the single. The dual is for safety reasons. If you lose all the fluid from one reservoir you will still have some braking power. I would give it a try it it were me.....

Tim

 

[Seattle66]

Thanks for the responses. I did some more research after posting and think it will work with the new MC and p-valve. What I think happened is that the original H-block was probably shot and so instead of a sourcing a new h-block the PO just used a proportioning valve that was basically wide open for the same front and rear brake setup as opposed to the kind needed for front discs and rear drums.

My only other minor issue is the fitting on one of the new brake lines that came with my kit doesn't fit the proportioning valve, but that is easy to remedy with an adapter. I can't wait to get it back together and test out the improved brakes.

 

[Pops68]

I just checked their website and Tom's sells the H block (used) for $85, if you want to go that route vs. the proportioning valve. Or I am sure someone has an extra one laying around. Possibly Delconick, the Great Justino, or Bronconut1 or someone else.

Also, I heard the larger MC reservoir is for the fronts (more weight with the engine) and the smaller one is for the rears....appropriate lines are different diameters, too (1/4" and 3/16"). Can't say for sure on this info though.

Hope this helps.

Pops

PS: If I am wrong about the MC info, I appologize!

 

[Apogee]

If you're looking for a distribution block with built-in adjustable proportioning valve and you're replumbing the truck, Wilwood has their #260-11179 and they're less than a used H-block from TBP apparently.

 

[Schloer2]

Is the TBP power brake kit a direct bolt on for a '72 with manual drums? I am considering purchasing a '72 but wouldn't feel safe letting the wife drive it without the added stopping power and would prefer a <$400 solution over dealing with a axle swap (for now at least).

http://www.tomsbroncoparts.com/product/power-brake-kit-no-modify-wdrum-brake-lines-new

 

[Timmy390]

I am considering purchasing a '72 but wouldn't feel safe letting the wife drive it without the added stopping power and would prefer a <$400 solution over dealing with a axle swap (for now at least).

I had power drums on my 74 for 10 years and they were OK but I never let my wife drive it. All the booster does is amplify any pull the front brakes have so if it's a small pull it will be a med pull with the booster and a med pull will be a large pull. If you ddin't know the rig, you could get into trouble quick.

Now if you take the time to rebuild the from drums and keep them adjusted properly then you will fair far better. I rebuilt my fronts and did adjust on them but not as I should have.

I went to Disc's over the past summer and the difference is night and day. My rig stops quick and straight. I went all ford but you could go Chey conversion, no axle swap needed. many many many guys on here running that conversion.

Tim

 

[Schloer2]

Thanks Tim...in your opinion do you think I would be better doing the disc conversion with no booster or add the booster and keep the drums. I will be doing this build on a budget so have to space out my spending.