Help me fix some Disgustang Brakes (Early Mustang Content)
An acquaintance of mine purchased a 1969 Fastback Mustang Mach I clone, with a big block 429 and Four Speed.
Car was originally built as a manual brake car – and has the original pedal box (and manual pedal) in it.
Car has CSRP Front Spindles, which use ~1975 Ford Granada Calipers and Rotors
Link to Spindles:
https://www.discbrakeswap.com/Mustang%20Disc%20Brake%20Conversion%20Kits%20SWAP2.html
Link to Existing Calipers:
Front Calipers are single piston, 66mm bore
Front Rotors are 11.03 diameter, with a .875 nominal thickness
Rear has a 9” with the dreaded Generic Cadillac-style rear disc swap calipers (85 Eldorado) and 11.25 inch diameter rotors with a .980 nominal thickness
Link to similar 9” rear disc setup:
Rear Calipers are single piston, with 54mm bore (and new, and adjusted properly)
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According to the owner, it always had “acceptable” brakes – up until on the way over to my Dad’s shop, the clutch z-bar rubbed a hole thru the hardline going to the rear brakes
He brought it over to install aluminum valve covers, and during install of said valve covers, it was noted that the incoming cast iron master cylinder wouldn’t clear the valve covers, so it needed to be replaced
However, whomever “restored” this thing last installed a generic, universal GM style booster and 1-3/16” bore C3-era Corvette master cylinder and prop valve. They drilled 2 new holes in the firewall to mount the booster / master, and used 2 of the existing holes in the firewall.
Long story short, after a lot of parts swapping, finding a bad booster, a stuck prop valve (turns out “acceptable brakes” means no rear brakes working at all!) and the aforementioned manual pedal in the power system, and the clearance issues with the big block and valve covers, all parties are in agreement to move to a manual brake system and ditch the janky aftermarket booster.
That said, I'm unsure as to appropriately size the master cylinder bore , and need the hive mind’s knowledge on how to size it appropriately
To further complicate things, long term, the owner wants to move to 99-04 Mustang GT calipers up front, and explorer rear disc using these kits:
https://www.discbrakeswap.com/Mustang%20Disc%20Brake%20Conversion%20Kits%20SWAP%204.html
The "future" upgraded brakes use Twin Piston Calipers with 45mm bores up front, and a single piston caliper with a 47.9 mm bore in the rear
Ideally, I’d like to find a master cylinder that would work OK for both – but if that’s not possible, I understand.
If anybody has any other suggestions as to brakes on this thing – please speak up. Only real constraint on this is that he wants everything to fit under a 15” wheel