Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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MG four six eight
Bill Jacobson
Wa state
(217 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: MG four six eight
Date: June 01, 2012 12:59AM

First off I would like to thank Rob (rficalora) for doing all the leg work to figure out which master clylinder(s) would work!

One of the drawback to the chrome bumper MGB 3/4" master cylinder is that it is a little small for big brake/4 wheel disc brake conversions. Even with residual pressure check valves installed I found the brake pedal travel to be "ok" at best. The challenge is to find a larger bore master cylinder that would fit in the stock location on a chrome bumper MGB.
Enter Rob's idea of using a 89 Camry master cylinder with a 86 Isuzu Trooper resevoir!
Parts required
86 Izusu Trooper master cylinder
89 Toyota Camry master cylinder
IMG_1683.jpg
Isuzu Trooper M/C on the left, Toyota Camry on the right.
IMG_1684.jpg
Note that the center to center distance for the resevoir ports are the same. However the Isuzu ports are a larger diameter. What I did was use the Camry seals and enlarged the holes using a 7/16" gasket hole punch. Also shown is the small aluminum retainer bracket I made to hold the Isuzu resevoir on to the Camry master cylinder. The idea here is to make the bracket short so the it holds the resevoir down tightly, for hood clearance and resevoir to M/C sealing. The Isuzu resevoir ports also had a lip on them which required hand filing/sanding to remove the lip.
IMG_1685.jpg
Isuzu resevoir installed on the Camry master cylinder.
IMG_1687.jpg
The Camry M/C comes with a 3 hole mounting flange that requires modification to fit the C/B pedal box. At first I was going to simply file down the flange to fit. Then I decided that since there is plenty of material on the flange, it would be better to just drill new mounting holes in the flange.


MG four six eight
Bill Jacobson
Wa state
(217 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: MG four six eight
Date: June 01, 2012 01:23AM

IMG_1688.jpg
Completed mounting flange modifications. Note I left one hole (the longer one) intact. It just happens that this flange buts up against the clutch M/C prefectly!
IMG_1689.jpg
Next on the list, is to convert a power brake M/C into a manual brake M/C. For linkage I was able to reuse the stock MGB push rod, sometimes it pays to be lucky! I left the MGB rod the stock length, if I was going to do another one I probably would grind approx 1/16" off of the rounded end to allow some brake switch free play adjustment. Instead I ended up grinding approx 1/16" off of the brake pedal where it contacts the brake switch, which worked out fine.
To retain the rod in the M/C piston I use a 1/4" snap ring and o-ring. Then made a tapered collar out of a 5/16" nut. I bored the nut out to allow the rod to swivel, which compensates for a slight arc of the pedal travel. Then ground down the outside of the nut to a taper which matches the taper of the inside of the M/C piston. Other mods included grinding down the "ears" of the snap ring slightly, which also helps the push rod swivel.
IMG_1690.jpg
Install taper lock and related parts. The boot is a stock MGB which fits prefectly (some more of that dumb luck)!!
IMG_1691.jpg
Connecting rod attached to piston. The taper sleeve is pressed into the M/C piston and secured with red locktite. I added a dab of grease to the end of the rod before pressing the whole works together.
The push rod can swivel around slightly but does not pull out of the M/C piston


MG four six eight
Bill Jacobson
Wa state
(217 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: MG four six eight
Date: June 01, 2012 01:33AM

IMG_1692.jpg
View of the M/C installed in the pedal box. For locating the M/C I used the stock hole, but positioned it as far down as it would go. This helps with hood clearance and more importantly locates the center point of the larger bore in the correct position vertically to correctly align it to the brake pedal.
Also it is a good idea to rotate the M/C slightly clockwise (when viewed from the front of the car). This helps with hood clearance at the LR corner of the hood.
IMG_1693.jpg
IMG_1694.jpg
Overhead view shows how the Camry M/C is just short enough to fit.
IMG_1695.jpg
Installed master cylinder!


MG four six eight
Bill Jacobson
Wa state
(217 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: MG four six eight
Date: June 01, 2012 01:41AM

IMG_1696.jpg

One last photo, most people don't even realize that its not the stock master cylinder!!
The car has Wilwood disc brakes front and rear and with the Camry master cylinder the brake pedal travel is "right there" and feels ideal!
Note I decided to leave the residual pressure valves in place, although with the 15/16" master cylinder I could probably run the car with out them.
The other kinda cool feature is the low brake fluid level sensor. SInce its there I went ahead and wired in a red LED warning light for a low brake fluid level indicator. The sensor is normally open and closes when the brake fluid level gets to low.



Edited 1 time(s). Last edit at 06/01/2012 01:45AM by MG four six eight.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(804 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: ex-tyke
Date: June 01, 2012 09:44AM

Excellent article, Bill.
This is the stuff that the MG conversion community feasts on!


mgb260
Jim Nichols
Sequim,WA
(1449 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: mgb260
Date: June 01, 2012 01:12PM

Great write up Bill!


MG four six eight
Bill Jacobson
Wa state
(217 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: MG four six eight
Date: June 01, 2012 08:18PM

Thanks guys! I figured that it would helpful for others to see how it was done.
The larger bore size opens up a lot more caliper sizing options and makes it easier to find matching front to rear calipers for the correct bias.
Cost to do the conversion wasn't to bad. Seemed like I only paid $89 for both master cylinders from Rockauto.com.

I'm not sure how many hours Rob spent researching/looking at different master cylinders, it had to be quite a few though!

Bill



rficalora
Rob Ficalora
Cypress, TX
(2038 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: rficalora
Date: June 02, 2012 12:26AM

Awesome write up Bill - way better than I could have done.

Actually, my pick a pull only charges $5 for used MC's so I scoured the lot with my son one day equiped with a CB pedal box, a cardboard template to show where the firewall recess & upper lip were, the Isuzu reservoir & a smart phone. Went up & down the isles looking at all the MC's... Any that looked like they'd work, we'd first check to see if the reservoir would fit & then went online @ RockAuto w/the phone to verify piston size if it wasn't cast into the MC itself. We spent 3 or 4 hours there & bought 5 if I recall. Then played with them back @ the garage to decide which would work best. All in all it was a fun activity & my son really got into it too. Hardest part was I lost the paper we wrote down which MC's came from which cars so for a long time I didn't know what we had. Finally found the paper just a few months back!


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(4226 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: BlownMGB-V8
Date: June 06, 2012 10:29PM

Most brake cylinders should have an internal residual pressure valve. Just another of those details we tend to miss.

Jim


MG four six eight
Bill Jacobson
Wa state
(217 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Installing a 15/16" bore master cylinder in a C/B MGB pedal box
Posted by: MG four six eight
Date: June 16, 2012 12:23PM

Good point Jim
From what I could tell when I had the Camry master cylinder apart, it did not contain a risidual pressure valve. I know that it does not hold pressure when bleeding the brakes and that the rear disc do not drag from fluid pressure.
It could be beause the Camry is a front wheel drive vehicle and that it may be desirable to not hold any residual pressure to the rear brakes, which could cause early rear wheel lock up. Also being front wheel drive the rear wheel cylinders tend to be smaller and have less fluid volume requirements.
Its something to think about when shopping for master cylinders though as a residual pressure valve for drum brakes tend to be in the 8-10 psi range, while disc brakes would only require 2 psi (if needed).
Link to a Toyota/Lexus brake training page that explains master cylinder operation. [www.autoshop101.com]

Bill


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