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willysmjeeps.com :: View topic - Dual Master Upgrade
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Dual Master Upgrade

 
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vuldub
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Joined: Jul 03, 2013
Posts: 20

PostPosted: Tue Jul 23, 2013 1:14 pm    Post subject: Dual Master Upgrade Reply with quote

Current setup
11" x 2" shoes, 11" drums all around (front and rear)
Front wheel cylinders 1 1/8" bore
Rear wheel cylinders 15/16" bore
Single reservoir master 1" bore
Firewall mounted master (upgraded)

Upgrade desired
Dual reservoir master

Several questions:
1) Will any dual reservoir 1" bore, firewall mount, work? I am eyeing a 72-76 CJ5 dual master wo/ power w/front drums.
2) What's the difference or desirableness about Herm's dual master?
3) Does the original 72-76 CJ5 have a proportioning valve (wheel cylinder bores are listed as 1 1/8" front and 15/16" in rear - same as my setup)
4) Can I do without a proportioning valve since my wheel cylinder bores are balanced for more front braking
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...Wes
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wesk
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Joined: Apr 04, 2005
Posts: 16365
Location: Wisconsin

PostPosted: Tue Jul 23, 2013 6:46 pm    Post subject: Reply with quote

Use Herm's kit. The master cylinder he uses is the stock dual master cylinder used under the floor by the CJ5 1969 thru 72. It's the simplist way and there no need for proportioning valves with that 69 to 72 set-up. The 69 to 72 used the 10" brakes but the 11's you have will work fine.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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vuldub
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Joined: Jul 03, 2013
Posts: 20

PostPosted: Wed Jul 24, 2013 7:11 am    Post subject: Reply with quote

Thanks Wes. My master cylinder is not floor mounted, it's on the firewall. The pedals on my m38 have been swapped out along with the steering column. Herm's master looks like it will bolt right into my firewall setup, however I would like to know the bore of the cylinder he uses. I need a 1" bore. I believe the CJ5's from 72-75 used a dual 1" bore equal sized primary and secondary reservoir. But I didn't know if they had a proportioning valve.
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wesk
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PostPosted: Wed Jul 24, 2013 8:55 am    Post subject: Reply with quote

If you plan on staying with a 72-76 CJ5 brake system it would be a good idea to get a 72-76 CJ5 parts and service manual. The 72 manual shows no proportioning valve. Only two residual check valves, one in each outlet port.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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vuldub
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Joined: Jul 03, 2013
Posts: 20

PostPosted: Wed Jul 24, 2013 10:59 am    Post subject: Reply with quote

wesk wrote:
If you plan on staying with a 72-76 CJ5 brake system it would be a good idea to get a 72-76 CJ5 parts and service manual. The 72 manual shows no proportioning valve. Only two residual check valves, one in each outlet port.
My 11" brakes were upgraded from a 72 CJ5 and the master is a single reservoir from a 66 ford pickup. I would like to replace the master with the 72 dual cylinder however I was unclear on the proportioning valve. Would the residual check valves be integrated with the new master or are they a separate part? I would love to get the service manual, however this jeep is now composed of parts from various vehicles requiring the purchase multiple service manuals.
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vuldub
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Joined: Jul 03, 2013
Posts: 20

PostPosted: Wed Jul 24, 2013 11:32 am    Post subject: Reply with quote

Thinking about this more, if I have drums all around and I buy a 72 dual master specific to drums w/o power booster, wouldn't the residual pressure valve already be setup inside for similar pressure (for drums) from both chambers?

PS> I found an 74 CJ5 service manual. Apparently the proportioning valve was added in 74 in a "combination valve" . 72 didn't have one.
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artificer
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Joined: Feb 16, 2007
Posts: 206
Location: Gold Coast Australia

PostPosted: Wed Jul 24, 2013 3:08 pm    Post subject: Reply with quote

Provided the master cylinder is firewall mounted use any firewall fitted Ford or GM 1" bore or other make for that matter.
With the correct size wheel cylinders no proportioning valve is needed so just forget about that aspect.

The master cylinders should be listed, on Rock Auto for example, as with or without residual brake pressure valves [2 for drum brakes or 1 to the rear line & none in the front disc brake circuit].

A master cylinder without 2 valves CAN easily be retrofitted with them.

http://www.rockauto.com/catalog/x,carcode,1120059,parttype,1836,a,www.google.com.au%2BSearch%2Bfor%2Bford

RAYBESTOS Part # RMC39468 More Info Reman
Master Cylinder (Remanufactured); 3/4 TON and 4 WHEEL/ALL WHEEL DRIVE Except FT DISC/RR DRUM,1" $12.71
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John GIBBINS
ASE Master Medium/Heavy Truck & Auto Technician 2002 USA
Licensed Motor Mechanic NSW # MVIC 49593 Current
YOU CAN'T TROUBLESHOOT WHAT YOU DON'T UNDERSTAND
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wesk
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Joined: Apr 04, 2005
Posts: 16365
Location: Wisconsin

PostPosted: Wed Jul 24, 2013 6:59 pm    Post subject: Reply with quote

Wes,

Quote:
Posted: Wed Jul 24, 2013 11:32 pm Post subject:
Thinking about this more, if I have drums all around and I buy a 72 dual master specific to drums w/o power booster, wouldn't the residual pressure valve already be setup inside for similar pressure (for drums) from both chambers?


Yes the 72 master cylinder has the residual valves built in to the outlet ports.

Since the brakes on the axles and the hanging pedals both come from a 72 Jeep then just stay with the 72 jeep parts and buy a replacement master cylinder for a 72 jeep CJ5 with 11" drums front and rear. Plumb it up and adjust the pedal rod and bleed and you are all set.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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vuldub
Member


Joined: Jul 03, 2013
Posts: 20

PostPosted: Mon Jul 29, 2013 1:39 pm    Post subject: Reply with quote

Great. Thanks guys. Two thumbs up.
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...Wes
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CapnDan
Member


Joined: Feb 24, 2009
Posts: 49
Location: Victoria,Texas

PostPosted: Mon Mar 20, 2023 10:57 am    Post subject: Reply with quote

Vuldub: How were you able to mount a master cylinder to firewall? Could you share how you did it, with a picture? Looking at my 54 M38A1 I don't see enough flat area above brake pedal to mount it.
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Danny L. Harris
aka Bubba
1954 M38A1
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RonD2
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Joined: Oct 02, 2014
Posts: 2004
Location: South Carolina, Dorchester County

PostPosted: Mon Mar 20, 2023 12:07 pm    Post subject: Reply with quote

Hi Danny,
Not sure if you noticed this thread is almost 10 years old?
His last post of any kind in this forum was going on 7 years ago.

Just a thought --- you might get better response by starting a new thread to ask your question?

Good luck!
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Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

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wesk
Site Administrator
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Joined: Apr 04, 2005
Posts: 16365
Location: Wisconsin

PostPosted: Mon Mar 20, 2023 2:31 pm    Post subject: Reply with quote

Here's a few links to folks that have been there, done that:

https://forums.g503.com/viewtopic.php?t=181801

http://earlycj5.com/xf_cj5/index.php?threads/144432/#post-1604134

https://www.jamcosuspension.com/product/universal-firewall-mount-power-brake-conversion-kit-pbbufw

As I recall there is quite a bit of room on the M38A1 firewall with the F134 engine for swinging pedals and a firewall mounted master cylinder.


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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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