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Brakes power brake booster swap

Brakes power brake booster swap
76cj7chick

76cj7chick

Old Time Jeeper
Posts
1,235
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1
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Location
WA
Vehicle(s)
1976 CJ7 Jeep with a engine/tranny/wiring harness out of a 1988 s10 blazer 4.3l v6 with th700r4 automatic tranny and a cj7 Dana 300 transfer case with Novak adapter.
Complete wiring harness from the s10 blazer. Painted with HOT PINK Pearl paint with standard sized metallic halographic pink flakes. Painted by me -a newb. New rear, front and side three wire LED lights, New parts, new custom dash-by me And a lot of guidance from fellow jeepers and lots of prayers etc.... :p
I did a front power disc brake conversion on my 1976 CJ7 jeep (originally manual drums) and want to know what power brake booster, mc and proportion valve I should use that doesn't require any mods?


Thanks in advanced.. 😊
 
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I've used an MC from a TJ and an adjustable equalizer. Worked for me. You'll have to modify the push rod.
 
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Thanks for the suggestion caveman. But I think I want to get a complete kit so I won't have to modify anything... Well, hopefully not.

Would you know if I can get a later CJ7 disc brake booster, mc and proportion valve? Would the rod need to be adjusted?

Thanks again for the help. 🙋
 
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Excellent question! How important is the relationship between the caliper bore and the master cylinder bore? Stock 80's CJ calipers have a 2.6" bore and the manual MC is .937" and the power brake MC is 1.00. Now, if you convert to disc brakes using a GM D52 type caliper with a 2.75" or 2.9" bore, which MC? Can an adjustable proportioning valve correct for the change in the caliper bore/master cylinder bore ratio?
 
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Oh boy, Bent... You lost me. 😯
But I sure appreciate your trying to help..

I bought the rotor and caliper kit off the eBay guy that sells lots of the jeep CJ7 front disc brake conversion kits. I could lol him up. Just can't remember his name off the top off my head.
 
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I looked the eBay seller up. I bought the CJ caliper conversion kit from Horsepower Sales-LLC although the kit was cheaper when I bought it a couple years ago. Unfortunately it doesn't say the bore size, but I could ask to see if he knows.

But he also sells a brake booster kit and the mc has a 1 1/8" bore.. So probably need to find a aftermarket kit with the same bore size.....or a later CJ7 jeep....

Or will an aftermarket kit with 1" mc bore size work without also needing an adjustable proportion valve?

I'm still learning about brakes.
So thanks for giving me a break and helping me out with my brakes. 😂
 
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I found some more information...
According to horsepower sale one of the calipers is part number 18-4045... However, I purchased Speed bleeder screws but the threads were 10mm and Not 3/8" as listed below.. I asked HP why they aren't 3/8".. And he said he gets whatever his supplier has at the time.

So who knows at this point? 😬
  • Piston Outside Diameter (in): 2.935 Inch
  • Piston Outside Diameter (mm): 74.549mm
  • Caliper And Pad Hardware Included: Yes
  • Bracket Mounting Bolts Included: Yes
  • Bleeder Screw Thread (in): 3/8-24 Inch
  • Inlet Port Thread Size (in): 3/8-24 Inch
  • Piston Inside Diameter (in): 2.433 Inch
  • Piston Inside Diameter (mm): 61.7982mm
Click to expand...

So, will a 1" mc or PV bore work without needing a adjustable proportion valve? Or is it trial by fire? 😳
 
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Well, I purchased a aftermarket brake booster kit off eBay.

Anyone have experience with this particular kit?

"1974-86 Jeep CJ8 " Dual Power Brake Booster Cast Iron MC Adj Combo valve" sold by gpsauto2010... Hopefully it's a direct fit... Well, even if I have to change out a few of the brake lines... But hopefully the soft pedal will become harder.

The kit comes with an adjustable proportioning valve... Not sure if it will have instructions... But I won't get the kit until September 9, 21.. So, in the meantime would anyone know how to adjust the PV?

THANKS AGAIN FOR YOUR HELP! 😘

PS. BENT, I now understand what you were sayN... Just took me some time to research... Boy, brakes are way more complicated than I thought they would be...
 
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1 1/8 MC bore seems to be about what was used with the 2.9" bore D52 calipers like the set in your kit. I think the same calipers were used on the 1975-ish wagoneers. Maybe the wagoneer MC will work with the CJ booster? The 1" CJ MC would probably work but you would also probably have more travel on the brake peddle.
 
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Thanks BENT for the reply! 😘

Unfortunately I'm not so good at math so wasn't sure what mc bore I'd need.. But I believe the YJ mc I have was a 7/8"...or smaller.. And the pedal was way to soft..
Anyways, I thought perhaps, good brakes are important. 😏
And so yesterday I purchased a aftermarket complete brake booster kit.. And I should get it September 9....
I bought it from gpsauto2010 on eBay. $239 free ship but 10.5% tax.. Washington State 😬😵
The seller has good feedback so am praying things will work out.

I opted to get the Adjustable Proportion Valve.... Hope it was the right move. But I think the mc has a 1" bore...

Thanks again for the help with the math..😉
 
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BENT, Thanks again for help with the math.
I will give an update when i get the kit which should be on 09/09/21 and after I install it. Hopefully the 1"mc bore is good enough, esp since I also bought the adjustable proportion valve...
Thanks guys for your help! 😘
 
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A bigger piston will move more volume, if you are going from all drum brakes which has a small volume pistons to disc which has larger pistons you need to move more volume i.e. bigger bore piston.
It is important to bench bleed the MC, it primes it and removes all the air so you are not introducing air into the system. Keep it full when bleeding, I bought a Mighty Vac kit from HF a few years back and it works everytime. Good luck.
 
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Thanks for sharing riversandsand. I hope a 1" bore is big enough. The booster assembly also includes an adjustable proportion valve so, perhaps I can tweak it until it feels right... I'll let everyone know once I get it and can install it.
 
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Hey Guys, I wanted to update everyone on the brake situation...
Eventually the master cylinder spacer/bullet fell out and that's the whole issues with the brakes. Once I installed it and my brother David helped me bleed the brakes again, now the brakes are nice and firm...

Thanks bunches!

PS. I don't recommend an adjustable proportioning valve as it doesn't have the emergency light switch (just a tail light brake switch). Of course I had to learn the hard way as I bought the key with the adjustable proportion valve... So, my emergency brake light is illuminating until I get the REAL PV on Wednesday.... But thankfully my brakes are good and firm.

I am disappointed somewhat as the master cylinder runs against my radiator support rod... But that means I just need to move it a inch or two to the driver-side.

Happpppppy JeeeeeeepN! 🚙
 
Last edited:
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Here the brake booster assembly all hooked up. 🚙

IMG_20211008_182736.webp
 
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Brock, some of those links will land you overseas.
 
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