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Today I installed a front disc brake conversion on my 1960 Vette using the stock single master cylinder. Aside for some minor problems, the installation was completed. I inadvertently left one caliper bleed open and drained the master cylinder. I bled the master cylinder and all the brakes. The front rotors rotated perfectly until I pumped the brakes. At that point, I could not turn them when the brakes were released. They were essentially locked up. A knowledgeable member of the forum said the restrictor valve in the master cylinder had to be removed as it was causing a retention of pressure. Another member of the forum said removing the valve was not required and had no problems leaving it in. At this point I am stumped. I'm planning on removing the end cap of the master cylinder and removing the restrictor valve IF I can remove the end cap which has so far been not successful. If I can't remove the end cap, my options are remove the master cylinder and rebuild it or get a new cylinder and prior to installation, remove the restrictor valve.
Any comments would be appreciated. I was hoping the rotors would turn with the valve in, but it's either that or something I'm missing.
Thanks, Captain Bud
Bill, I call it a restrictor valve, you call it a residual valve. Are we speaking of the same thing in the master cylinder?
whatever we care to call it, it's a small valve to keep a minimal amount of pressure in drum brakes so that the pistons don't need to travel as far in repeated applications. disc brakes don't need this as there is minimal travel of their pistons each time.
if left in, the valve will cause disc brakes to drag. I had this problem when I converted to front discs. in my case the drag was not severe but it caused the front brakes to squeal a bit because the dragging pads; particularly noticeable in slow traffic, and I could hear it with the windows down.
You could install a 10 pound residual check valve in the rear brake line only and a 2 pound valve for the front brakes if you need to get a better brake pedal feel . Most of the time the front doesn’t need any.
No it didn’t. If the rears lock up before the fronts, I’ll install. Since the fronts do about 75% of the braking, I should be ok.
I was just curious because I added front disc's to my '63, (along with a dual master cylinder) and it required a proportioning valve to adjust the pressure on the rear brakes. I did use the '65-'82 calipers however.
I was just curious because I added front disc's to my '63, (along with a dual master cylinder) and it required a proportioning valve to adjust the pressure on the rear brakes. I did use the '65-'82 calipers however.
Good luck... GUSTO
i used 65 calipers on the front of my 62, with the drums on the rear. used the single m/c with the only change being to remove the residual valve. never had any problems with the rears.
if the drum rears lock up before the fronts when braking, then a proportioning valve is necessary. otherwise not needed
I was just curious because I added front disc's to my '63, (along with a dual master cylinder) and it required a proportioning valve to adjust the pressure on the rear brakes. I did use the '65-'82 calipers however.
Good luck... GUSTO
I'm still using the single master cylinder. I'm one of those who wants to keep it as original looking as possible. I'm good with your reply except for the "good Luck" part.
I'm still using the single master cylinder. I'm one of those who wants to keep it as original looking as possible. I'm good with your reply except for the "good Luck" part.
Sorry about that... it's just my normal salutation...
Sorry about that... it's just my normal salutation...
I'm sure it won't be needed.
GUSTO
No problem. I was just hoping you knew something I didn't know. My wife won't drive in it until I do the Fantom Works 3-2-1 panic stop. I haven't put the wheels back on yet to test the new system because the brake pedal still feels spongy. I bled the master cylinder and wheels twice. I suppose I will actually need your "GOOD LUCK".
05-23-2018, 09:13 PM
Disc brake conversion
