Master cylinder

[RFRANK #44579]

I am converting my 63 fronts to disks. Ordered complete kit from VBP. My original 63 master cylinder is leaking. Question is since I need to replace should I change to a 67 dual master cylinder and if so will I need to change the original break lines? If I do not change to a dual master cylinder am I better off getting a new 65 single master cylinder since it is larger than the original 63?

[mike cobine]

Re: Master cylinder

Since the pressure and fluid requirements are different on disk brakes and drum brakes, I think you find you need something like the Chevelle or Impala dual master cylinders.

One reason is that you need the check valve for the drums and none for the disks. I think John Hinckley has mentioned that on here before.

I'm surprised the VBP kit doesn't address this in their docs.

[John H.]

Re: Master cylinder

If you use your '63 master cylinder, you'll have to remove the residual pressure valve from it and install an aftermarket 10# RPV in the rear line, downstream from the block on the frame. If you use a '65 single-reservoir disc brake master cylinder OR the '67 dual-reservoir master cylinder, you'll also need the RPV in the rear line downstream of the block.

A better bet is to use a dual-reservoir master cylinder for a factory disc/drum system (Chevelle, Camaro, etc.) - it will be set up properly with an RPV already installed in the rear outlet and none in the front outlet, and will have the proper fluid displacement capacity in the bore.

[Gary C.]

Re: Master cylinder

Converted my '64 to front disc brakes and used all '67 Corvette parts; i.e. dual power master cylinder, calipers and rotors. Left the '64 drums on the rear enplace. Ran all new lines to front and rear. Used a proportioning valve inbetween the master cylinder and the rear drum brakes which keeps them from locking up due to the increased pressure needed for the front discs.

CAUTION - the dual power master cylinder did not clear the hood when installed in the original '64 master cylinder mounting holes on the firewall. Never measured a '67, so I don't know if the mount holes are lower or ? The '67 Corvette power brake booster and master cylinder angle up. The tip of the nose of the master cylinder barely keeps the hood from closing. I elected to pop a new hood using a '67 hood for a mold without the center brace. Made it thinner than the original hood so it would close. Didn't explore the option of redrilling the holes in the firewall and mount the unit lower which might have been quicker and easier to do.

My '64 stops on a dime. So good enfact, if you really get on the brakes hard the stop can be a little hairy.

Good luck,

Gary
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