Want Power brake booster swap and keep drum brakes?

[76cj7chick]

I am wondering if it is possible to swap out my manual brake reservior and install a master cylinder reservoir and booster from a 88 blazer s10 into my 76 CJ7 ?

For now want to keep my 4 drum brakes. Would this swap cause an issue? Also, being a 4wd SUV do I need "special" boosters/Mc???

Would anyone know what mods are required to do the swap?

Do I use the brake proportional valve from my cj or the blazer?

I will have to relocate the proportion valve that is on the cj frame as it is currently in the way of the exhaust for my engine swap (4.3 v6 from the blazer)

What is the easiest way to extend the brake lines after I remove the proportion valve???

I have the brake pedal and bracket from the blazer (same vehicle that I got the engine and Transmission from).


Pictures and step by step instructions are the best!
Thanks ahead of time!

 

[mriplaybass]

This is more opinion than fact, but isn't that what we love about our jeeps?
If memory serves me correctly, the 88 Blazer was disc/drum. If so, does your MC have 2 different sized reservoirs? The larger would be for the disc, and the smaller for the drums. Typically, drum/drum MC's would have the same size reservoirs. Trying to use the CJ proportioning valve if it was originally set up for drum/drum could produce unwanted, or unpredictable results in a drum/drum application. I would switch out to an adjustable proportioning valve if you decide to go with all the Blazer components. At least then you can compensate for any irregularities in the conversion. Naturally, make sure the Blazer components are in A1 condition before using any of it. Don't skimp on your brakes! I know there are varying opinions on the nickel/copper brake lines, and I was hesitant to use it myself, but my research indicates that this is every bit as safe and strong as steel, and several European manufacturers use it as OEM equipment. It bends like warm butter, and does not rust. I put it in all my vehicles, some getting very heavy duty use, and it works great. Make sure you double flare all new brake lines.

 

[76cj7chick]

This is more opinion than fact, but isn't that what we love about our jeeps?
If memory serves me correctly, the 88 Blazer was disc/drum. If so, does your MC have 2 different sized reservoirs? The larger would be for the disc, and the smaller for the drums. Typically, drum/drum MC's would have the same size reservoirs. Trying to use the CJ proportioning valve if it was originally set up for drum/drum could produce unwanted, or unpredictable results in a drum/drum application. I would switch out to an adjustable proportioning valve if you decide to go with all the Blazer components. At least then you can compensate for any irregularities in the conversion. Naturally, make sure the Blazer components are in A1 condition before using any of it. Don't skimp on your brakes! I know there are varying opinions on the nickel/copper brake lines, and I was hesitant to use it myself, but my research indicates that this is every bit as safe and strong as steel, and several European manufacturers use it as OEM equipment. It bends like warm butter, and does not rust. I put it in all my vehicles, some getting very heavy duty use, and it works great. Make sure you double flare all new brake lines.

Hi mriplaybass!
Looks like you're right. The blazer resivour has two different sizes and the cj has two the same size.
Could I use the proportion valve off the blazer?
Just exactly what does the proportion valve do anywsys?
If not, could you ring in and let me know of what to look for in a brake proportion valve with adjustable switch?

I wouldn't want anything scary or dangerous to happen


Thanks for your help! Keep the comments/suggestions coming please!

 

[mriplaybass]

Simply put, A P/V balances the flow and pressure between front and rear brakes. Disc brakes have a much larger piston, hence the larger reservoir. You could not use a drum /drum MC on a disc setup. Not enough fluid capacity for the large disc piston. However, it is possible to use a disc/drum MC on a drum/drum setup. You will just not be using the full fluid capacity. I would use a 5 port P/V, 2 in, 3 out.
You can't use the Blazer PV. It is preset for the Blazer setup. You will flow too much fluid to the front resulting in the front brakes grabbing sooner than the rear. This will lead to loss of steering control on slick or loose surfaces. You want the rear to apply slightly sooner than the front. Maybe 55/45. This is my opinion on your conversion. Maybe someone else can chime in if I am wrong.
All that said, I have a few recommendations for you. I am amazed at your mechanical abilities! But, you seem a novice at brakes. I recommend rebuilding or replacing the stock components rather than venturing into an area you are unfamiliar with. If you are planning on larger tires, do a front disc conversion. You can get the MC/booster/fire wall bracket on eBay for $169, and the disc kit for around $550. Or find a doner axle for a lot less. Then you have a bullet proof setup. If you decide to go ahead with the Blazer conversion, as always, we will all continue to help as much as we can.

 

[IOPort51]

check out a 70s corvette drum/drum, disk/disk master cylinder, it will fit on the power booster.

 

[76cj7chick]

Simply put, A P/V balances the flow and pressure between front and rear brakes. Disc brakes have a much larger piston, hence the larger reservoir. You could not use a drum /drum MC on a disc setup. Not enough fluid capacity for the large disc piston. However, it is possible to use a disc/drum MC on a drum/drum setup. You will just not be using the full fluid capacity. I would use a 5 port P/V, 2 in, 3 out.
You can't use the Blazer PV. It is preset for the Blazer setup. You will flow too much fluid to the front resulting in the front brakes grabbing sooner than the rear. This will lead to loss of steering control on slick or loose surfaces. You want the rear to apply slightly sooner than the front. Maybe 55/45. This is my opinion on your conversion. Maybe someone else can chime in if I am wrong.
All that said, I have a few recommendations for you. I am amazed at your mechanical abilities! But, you seem a novice at brakes. I recommend rebuilding or replacing the stock components rather than venturing into an area you are unfamiliar with. If you are planning on larger tires, do a front disc conversion. You can get the MC/booster/fire wall bracket on eBay for $169, and the disc kit for around $550. Or find a doner axle for a lot less. Then you have a bullet proof setup. If you decide to go ahead with the Blazer conversion, as always, we will all continue to help as much as we can.

Let's say, later down the road I want to convert the front to disc brakes, Would it be wiser to wait until then before changing out the Mc and booster-so I dont have to do it twice? Or can I get the correct p/v and install the blazer MC?

Good to know what that darn brake p/v does.

Thanks for your continued help.

When looking for a donor axle, what should I look for and what gear ratio should I stick around if needed too? (I have the Dana 30 in the front with 3.54 gear ratio and the Dana 20 in the rear)

Thanks for the compliment.. But in all honesty wish I was quicker at learning all this stuff.. This build would go way faster with a "in-person mentor" but I don't have one here so I am thankful for all of the help I get from all the people on this forum!


Sorry for all of the questions... But thanks for the help.

 

[76cj7chick]

check out a 70s corvette drum/drum, disk/disk master cylinder, it will fit on the power booster.

Hey IOPort5 (interesting name)


Thanks for your suggestion. Is this something you have done yourself? You wouldn't have some pictures and instructions on how to do this upgrade would you?

 

[mriplaybass]

Let's say, later down the road I want to convert the front to disc brakes, Would it be wiser to wait until then before changing out the Mc and booster-so I dont have to do it twice? Or can I get the correct p/v and install the blazer MC?

Good to know what that darn brake p/v does.

Thanks for your continued help.

When looking for a donor axle, what should I look for and what gear ratio should I stick around if needed too? (I have the Dana 30 in the front with 3.54 gear ratio and the Dana 20 in the rear)

Thanks for the compliment.. But in all honesty wish I was quicker at learning all this stuff.. This build would go way faster with a "in-person mentor" but I don't have one here so I am thankful for all of the help I get from all the people on this forum!


Sorry for all of the questions... But thanks for the help.

You can get a generic PV which should work for both.
I am not positive, but you may be able to just swap the brake parts from one axle to the other. Maybe someone else can verify this? As for gear ratio, it all depends on what kind of driving you plan to do. 3.54 is a fairly good around town / mild off road ratio.

 

[IOPort51]

Hey IOPort5 (interesting name)



Thanks for your suggestion. Is this something you have done yourself? You wouldn't have some pictures and instructions on how to do this upgrade would you?

My friends call me IO

I went with 4 wheel discs w/power boost but is is basically the same thing. It was a challanging mod.

I had a Chevy with power drums when I was a kid, did a panic stop one night and bent a drum.

 

[76cj7chick]

You can get a generic PV which should work for both.
I am not positive, but you may be able to just swap the brake parts from one axle to the other. Maybe someone else can verify this? As for gear ratio, it all depends on what kind of driving you plan to do. 3.54 is a fairly good around town / mild off road ratio.

I think I am so far happy with that ratio as I would like to drive the cj as my dd and then do some offroading but it will primarily be a dd.
I may have to find a generic PV then thanks for the advice.

 

[76cj7chick]

My friends call me IO

I went with 4 wheel discs w/power boost but is is basically the same thing. It was a challanging mod.

I had a Chevy with power drums when I was a kid, did a panic stop one night and bent a drum.

Hey IO

Nice clean/organized jeep.

Wow! You bent a drum? You must have super powers in your legs.

 

[IOPort51]

Hey IO

Nice clean/organized jeep.

Wow! You bent a drum? You must have super powers in your legs.

organized maybe , very seldom clean. I try to keep things organized enough that I could find a problem on a rainy night in the center of no place. I am sure I failed in this but give it my best shot.

Adrenalin, A drunk pulled in front of me and I just barely missed him.

 

[76cj7chick]

organized maybe , very seldom clean. I try to keep things organized enough that I could find a problem on a rainy night in the center of no place. I am sure I failed in this but give it my best shot.

Adrenalin, A drunk pulled in front of me and I just barely missed him.

Scary!!
Glad no one got hurt!

 

[Kane]

I don't see anything on here regarding the residual valve. A drum requires a stronger residual pressure valve. I believe the disks are 2 pounds and the drums needs about 6 or 8. The front drums will retract if you only have the 2 pound valve so when you press the brakes the pedal will go to the floor until the shoes reach the drum.

 

[mriplaybass]

I don't see anything on here regarding the residual valve. A drum requires a stronger residual pressure valve. I believe the disks are 2 pounds and the drums needs about 6 or 8. The front drums will retract if you only have the 2 pound valve so when you press the brakes the pedal will go to the floor until the shoes reach the drum.

Kane is correct, a residual valve, or combination of valves would be used to prevent the drum shoes from contracting due to return spring pressure.

DRUM BRAKES FRONT AND REAR WITH MASTER ON FIREWALL OR UNDER FLOOR

• drum/drum, firewall or under floor

Drum brakes require a 10 lb. residual pressure (RPV10) to counteract the spring tension in the drum system which tends to pull the shoes away from the drums. This will give you a longer pedal travel and "spongy" brakes. The residual valve holds a pressure keeping the shoes near the drums giving a higher firmer pedal. Also required a metering valve (PVM) to the front (the metering valve prevents nose dive).

Although some people do not use the valves and have brakes that function just fine, (my self being one of them ). The correct way of doing the set up is to use the valves. When or if you decide to convert to front disc brakes, you would replace the 2 front 10psi valves with 2psi valves. Each valve costs from $10 to $20, and can be found at just about any supplier, Summit, Speedway, eBay, etc. The adjustable PV would go where the above picture shows a metering valve, and the rear brake line would go to the PV first. The above picture is for illustration purposes only. A 5 port PV is obviously plumbed differently so as to allow control of both front and rear brakes. Sorry for the omission. Thanks Kane!

 

[76cj7chick]

Hmm. Looks like I don't have any RVs...

The only two things I can find is the brake fluid resivoir and brake PV... Perhaps the residential valves are hiding somewhere???

 

[IOPort51]

The residual valves lurk in either the PV or the MC.


I think you will need a drum, drum PV.

you do have one of those, do you not?

 

[tarry99]

The residual valves lurk in either the PV or the MC.


I think you will need a drum, drum PV.

you do have one of those, do you not?

As IO alluded to in a Modern correctly spec. Master Cylinder or Brake Proportioning valve......... the Residual valves are internal.

Brake systems are all about moving hydraulic fluid volume and creating pressure to do the work , therefore the correct bore size in the donor Master Cylinder should be matched to whatever brake system your using..........as will as the pedal ratio which will be different for a manual vs a Boosted system.

 

[mriplaybass]

I agree with Tarry and IO, as I stated, I do not have external residual valves on my setup, and my brakes work great. Given the fact that you are trying to use a disc/drum master cylinder on a drum/drum set up, you could encounter problems. I ran that risk with my set up, so I proceeded with caution until I had everything balanced out. There was some initial undesirable braking which the adjustable PV took care of. Another reason for residual valves from what I have read about them is, they are necessary if the master cylinder is located below the floor level.

 

[76cj7chick]

The residual valves lurk in either the PV or the MC.


I think you will need a drum, drum PV.

you do have one of those, do you not?

Good to know that they are hiding in the PV or mc . Yes, the PV on the jeep is drum/drum. Don't know if its adjustable though. Believe its the stock cj PV. So it may not be adjustable.