Drum to disc master cylinder question on '69 442

[drmatera]

ok fellas here is my situation. My 69 442 has 4 wheel drums

I'm in the process of rebuilding the front suspension with the Ridetech arms and spindles. I am going to pick up a Wilwood or Baer 13" front set up so here is my question: Can I use my existing master cylinder for a time? I understand the residual pressure for disc vs. drum is different but where is that handled, in the MC or is there a distribution block? I will eventually be adding discs to the rear as well and will be switching to a hydroboost at that time.

I appreciate any insight

[a67]

For a '69, it is likely that the residual pressure check valves are in the M/C. I've pulled my fair share of them over the years. To remove them, disconnect both brakes lines from the M/C. There should be brass inserts for the flair seat in the M/C.

Use a sheet metal screw and thread it somewhat into the brass insert. Then using two large flat blade screwdrivers carefully pry the seats out. Using a long nose pliers reach into the M/C and grab the rubber seal and pull it out. A small spring should have also come out with it. If not reach in and grab it.

Press the brass seats back in and reconnect the lines. Done.

Bob.

[drmatera]

Great, Thanks Bob. So if i'm just doing the front disc conversion now should I leave the insert in the rear line until I do the rear swap? Thanks again

[Apogee]

Great, Thanks Bob. So if i'm just doing the front disc conversion now should I leave the insert in the rear line until I do the rear swap? Thanks again

That is correct. Since you most likely don't have the original MC in the car still, use a paper clip or something similar to first confirm that there are residual pressure valves in the outlet ports before you assume there are, as some remanufactured units have them and some do not. That said, the assumption is that the 1" bore MC will be suitable to whatever front disc kit you choose may be a poor one, as the appropriate MC bore size should be a function of caliper piston area and several other variables including manual versus power, pedal ratio, rotor diameter, pad CoF, etc.

Odds are the 1" bore unit in a manual configuration will stop the car, just not all that impressively, and lockup may not even be achievable up front with aftermarket performance disc brakes.

Tobin
KORE3

[drmatera]

The car currently has power drums at all 4 corners. My ultimate objective is to run 4 wheel disc and do plan on converting to Hydroboost once I tackle the rear disc conversion. I only plan on running the stock master with the disc brakes for a short time while money and time build back up for the next round of mods

[Apogee]

That should be fine with vacuum assist assuming your engine has respectable vacuum levels.

[drmatera]

ok, well I finished up the 14" Wilwood brake install. As I went to do the MC mod I found the brass insert and pulled it out but there was nothing behind it. Now this car had drums up front when I bought it but do you suppose if the MC has been replaced at some point it was set up for disc/drum? So I guess I can just file the brass insert back into shape and stick it back in.

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