Re: Master Cylinder for a \'65
I'm putting one in my '66 J 2600 right now. There are two ways to go about it:
1) The simplest is to remove the single chamber cyl and bolt in a later model dual chamber cyl (will directly bolt in) while also replacing the distribution block that all the lines run into (now you have two lines running into the block instead of one), bleed using the technique for whatever year block you install.
2) If you are going to add vacuum boost like I am, it is more involved. May as well pick up a dual chamber vacuum boost instead of the single chamber. Mine was off a '75 J20 (identical to a 1/2 ton '75 chevy), you will also need the aluminum block that mounts it to the fire wall and I will describe the process to fit it:
-with the single resevoir removed, fit the mounting block to where the resevoir was located. Note that the two middle bolts of the block will match the two (upper) holes where the cylinder was located. While holding the block with the two middle bolts located at the cylinder mounting holes scribe the center of where the other two bolts holes will need to be drilled through the fire wall. Where the rubber boot of the vacuum booster will go through the firewall you will need to file that opening wider, from the engine compartment you will see there is plate welded to the firewall that has an opening a little wider than that the opening in the firewall and you can just file the firewall open to match the plate to get enough clearance, check the fitment and you should be good to go.
I am replacing my dash with a later model and using later model brake, clutch and throttle pedals so with this set up it requires pulling the two cylinder holes down 1/4" prior to scribing and drilling the last two holes, fab a mount to weld on for the upper dash support, file out the throttle cable hole to a square for the firewall plug and drill 3 holes for the throttle pedal mount. I'm still monkeying with the setting up the late model steering column, but it looks like I can just drill to mount the newer firewall plate to the old one and caulk to seal. I'm swapping in power steering from a '75 also.