Master Cylinder Upgrade

[fe468stroker]

When in doubt contact the experts right?  Some background info:  Car is a 1968 Mustang with a 427 Genesis originally a C code no power anything.  Now it has 1970 Torino Cobra front discs and 1974 Mercury Montego rear drums ( 10 X 2 1/2") all manual.  The master cylinder is from a 1974 Mustang 2 with a 15/16 bore, manual disc brake.  Best I remember is that the rear drum wheel cylinders are 1 1/8" bore.  Just installed a Wilwood adjustable proportioning valve also.  The master has a spongy feel so I need to replace it.  Been told that for the best stopping power the master needs to be the smallest bore possible and the wheel cylinders need to have the largest bore possible.  What would be the best master cylinder to use in this application?

[TomP]

Too small a bore on the master will take too much pedal travel and feel even spongier. 15/16 should do fine, Rangers come that way with manual brakes and their rear wheel cylinders are smaller. I don't have any but think they are under an inch. Single piston calipers are also probably a comparable size to those Torino calipers. Make sure sponginess isn't the rear shoes being too far away from the drum.

[winr1]

"Spongy feel" ...if ya pump the pedal does the pedal get firmer or stay higher ??

Did ya bleed the master cyl. off the car ??

Was the pedal spongy before and after ya installed the Wilwood adjustable proportioning valve ??


Torino calipers may not be the same but on 73 to I believe 79 F 150s, the front calipers have a left an right
If installed wrong, they canna be bled properly


Lastly, how does the car stop at the moment ??



Ricky.

[CV355]

Did you bench bleed the MC?  You can do it in the car, it's just a pain to swap out the lines without making a mess. 

MB Bore:  1 1/8" is ideal with a booster, and 7/8"-15/16" bore is ideal for manual (non-power) brakes.

[Keith Stevens]

Factory Mustangs come with 15/16" bore for manual and 1" with power assist from Ford. I have factory Kelsey Hays four pistons up front and 11X2.5 rear brakes with 31/32" rear cylinders. The pedal is where it belongs and stops well.

[fe468stroker]

The brakes were spongy before the Wilwood was installed.  Figured the master was on it's last legs so now was the time to redo the whole system.  Replaced the rear shoes, wheel cylinders and the flexible line at the rear end.  I've got a 15/16 master coming so hopefully that will take care of the problem.  I know it's not going to stop like a modern car with ABS.  Thanks for the input.

[GerryP]

I don't know if this will help anyone working brake issues, but if you have a Fairlane/Mustang with the iron master cylinder and are in need of replacing it, the master cylinder off a 1986-1990 Bronco/Ranger is a direct fit replacement.  They come in both manual and power brake models.  The only difference between the old iron and the Bronco master is the position of the front brake line.  It moves from a bottom exit to the side.  The pushrod depth or the pushrod length, the mounting dimensions …everything is the same.  With the exception of that front brake line, the master cylinders are an exact fit.  They are aluminum construction with a clear plastic reservoir.

Here's the power brake model RAYBESTOS MC39567 at Rockauto for 30 bucks new:  https://www.rockauto.com/en/moreinfo.php?pk=309758&cc=1106187&jsn=502  I got a Dorman M39567 power brake cylinder on Amazon for 35 bucks for my '67 Fairlane.  Works like factory.  About half of the cost for what an iron cylinder runs.  And rebuild kits for those iron cylinders seem scarce and pricy when you can find them.  They must be made of lumber or something. 

[Falcon67]

Same as above - 15/16 is fine.  1" would be too large.  I used iron cylinders for manual disk/drum and haven't had any issues.  The 75 Maverick MC has been on the Falcon for over 30 years, 20 of that racing.  No problem stopping 3250 lbs from near 100 MPH in the 1/8 mile.  The aluminum Ranger cylinder should also be a good piece.  On the manual vs power - one difference to watch for it that typically power cylinders use a very short actuation rod and a different internal piston.  That was true on the iron units.  The newer aluminum ones maybe not. 

Note on MC bore size - smaller = longer throw with higher line pressure.  larger = shorter throw/lower line pressure (high stiff pedal, poor manual braking)

I looked at one time and was not able to come up with a "real" part number for a manual Ranger aluminum cylinder.  Never seen a Ranger with manual disk/drum either.  Somebody ordered a late 80s, early 90s Bronco without power disks?  Really?  Just askin LOL. 

[GerryP]

...
I looked at one time and was not able to come up with a "real" part number for a manual Ranger aluminum cylinder.  Never seen a Ranger with manual disk/drum either.  Somebody ordered a late 80s, early 90s Bronco without power disks?  Really?  Just askin LOL.

Look up an '89 Ford Ranger (or anywhere in that '86-'90 range) on Rockauto.  All will be revealed.

[Falcon67]

I'll go look in my Wagner and Raybestos books also.  Thanks!

[TomP]

Earlier Rangers, like 1984-85 have an aluminum master that looks just like a 60's master. Same lid with the wire bail over top. If you want it for light weight watch out for replacements, they could be iron. Some will list in the specs if it's aluminum or iron on the Rock Auto site.