1937 master cylinder conversion

[VooDoo]

Wondering if anybody has a solution to convert a 1937 75 series master cylinder to a duel master cylinder? I talked to Art who makes kits, but the mounting brackets are different for the large bodies (triangular) so his kit won't work. Anybody have a solution or a good dual master cylinder they can recommend? Thanks.

[VooDoo]

Anyone have a solution?

[Caddy Wizard]

I think the answer is pretty straightforward, but is not something I currently offer.


The original master has a triangular mounting flange on the end.  Find a dual circuit master and make a thick metal plate to act as an adapter to go between the flat panel to which the original master is mounted and the new master.  One side of the plate would have a hole pattern (or stud pattern) to match the new master and the other side of the plate could have the hole pattern (or stud pattern) of the original master.  So you would bolt the new master to the adapter plate and the adapter plate to the original mounting panel.

Depending on the positions of the holes or studs, you might be able to co-locate one of the three holes/studs for the original master with one of the holes/studs for the new master.

If there is enough adjustability in the original pushrod, you might be able to adjust it to reach the new master and have the proper minor clearance without replacing the pushrod with a custom unit.  Otherwise, you might have to make a custom pushrod to reach an extra 3/8 or 1/2 inch (the thickness of your adapter plate).

My existing kit for the 39-49 cars works with a particular Wilwood master -- Wilwood Part number 260-7563.  This master has internal valving for 4 wheel drum brakes, but can be switched to front disk and rear drums in a minute by reversing a valve or two.  Very good master for an old Cadillac.  This master uses remote reservoirs that can be mounted up high for easy access and inspection.  If you want a master with a reservoir on top, you might need to search for another master.

[VooDoo]

Thx Art 😁👊🏼

[fishnjim]

The single system typically mounted on the frame rail from side and the pedal linkage was in line with the plunger.  The later duals were typically mounted on a booster or firewall, so the mounting holes are not side mounted typically.   There's the rub in finding an off shelf solution.   And how many of these are needed, makes a commercial supplier cringe.
I decided to bite the bullet when dealing with the booster failures on the '58 and went with a modern system adapted for disc, but kept the drums, ie, rip out the factory stuff.  I put a repro in the "P" but it had issues after a few years.  If I ever complete the conversion, I'll put a modern frame in.
I don't "do" pre-war, but been around, you might want to search around the hot rod suppliers as it's been done many times, but may have included surgery.  I don't think you'll find a bolt-in option based on my earlier research for the "P" and '58.   Some of the singles are even scarce to find in repro.  Most likely outsourced if you do.
Due respect, I can see an adapter plate could cause alignment issues.  Getting the bolts to align without thickness is the issue ex cutting the frame and welding the adapter plate or stiffened bolt "holes" in it's former place as factory.   Welding a frame, that's always a tricky proposition, is it strong and safe to operate...   Most DIY shops don't have Xray equipment handy.  Consider to enlist a certified welder.  Heat destroys strength and temper also.
ps: FYI, I didn't like the tremendous liability of producing or installing braking systems, myself, and farmed it out, even though I was capable.  If there's an accident and the brakes were "modified" since that's a DOT issue, that's a cause for legal action.  Even though a tempting to make it safer.  Insurance is a must here.   I know all the argument +s and -s, so just informing for a clear conscience.   Ingenuity's one thing, applying it is another.