68383GTS
Well-Known Member
Done this conversion twice over the years but can not remember what mastet cylinder I used. Converting to manual disc brakes. Also what proportioning valve... Thank You
Manual disc brakes, master cyl?
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68383GTS
Well-Known Member
Sucks getting old...
kiss
Well-Known Member
69_340_GTS
Well-Known Member
Use the smallest one you can get, around 15/16" or 7/8". I did not use a prop valve. It isn't usually necessary with 4 wheel discs on these light cars.
68383GTS
Well-Known Member
Ya I never used a prop valve on my two other conversions.So just a manual master cyl or a disc brake master cyl? Cant remember
Inertia
Well-Known Member
I've used both "power brake master cylinder" and the "manual brake master cylinder". Both worked great. Difference is, the power MC pushes easier to stop but has more pedal travel.
69_340_GTS
Well-Known Member
Doesn't matter. Just get the one with the small 15/16" or 7/8" piston.
Inertia
Well-Known Member
You didn't say you were using 4-wheel discs. If not, you probably do want a proportioning valve, because drum brakes increase braking force disproportionately with pedal pressure, while discs are proportional -- this means in a panic stop the drums will tend to lock first. What 318willrun said is correct, in that the factory equipped the small (15/16) bore with power disc brakes, and the big bore (1+, depending on year) with manual disc brakes. Summit makes a reasonably priced proportioning valve, as well. Tip: to install the PV without having to cut and flare lines, buy a short section of generic brake line with the correct fittings at your local auto store (16" or so will work) and bend it into a loop. Then mount the PV directly next to the safety switch block. Just undo the rear brake line output from the block and into the output of the PV. Then install the new loop so it connects the input of the PV to the now vacant port on the block. I see a lot of people installing the PV between the master cylinder and the safety block, but the factory put it after the block in the line going to the rear brakes. I am guessing this was to avoid the operation of the valve affecting the brake warning light, although that probably isn't critical.
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