427390HP

I'm helping my brother get his 63 convertible back on the road after an extended hibernation. One of the things we'll be doing is a complete redo of the brake system.

I've read most of the threads in the archives over the last 10 years about converting a 63-64 single to dual master. I know many people here have gone to front disc or 4 wheel disc. We're aware of all the reasons for a disc upgrade but, at this time we don't want to do a disc conversion, so let's please skip that discussion.

Of course the 63 single has a 7/8" bore. I have found several dual masters with a 7/8" bore, primarily 1967-68 Camaro, Chevelle, Nova, and Corvair that came with drum brakes. My problem is that all of the remanufactured or reproduction masters for those cars are all 1" bore. I'm also aware of the significant pedal feel difference by going from a 7/8" bore master to a 1" bore master. We're not interested in that option either.

So, essentially my question is has anyone with a 63-64 Corvette found an available and reasonably priced dual master cylinder with a 7/8" bore that will bolt up in place of the OEM single?

Terry

Avispa

https://www.summitracing.com/parts/ado-18m1065

Give that one a look. Seems like it will fit.

427390HP

Thanks, but that is a 3/4" (.750) bore. Gotta have 7/8" (.875).

Avispa

Picky, picky....lol

https://www.summitracing.com/parts/dhb-m99084
https://www.summitracing.com/parts/ado-18m116

The only issue you might have with these is the ports are toward the engine. A little brake line routing might be needed, but they should work.

Personally. I'd do the 3/4 bore cylinder for manual drum brakes. Nice, easy, light pedal with a long stroke. Not at all tpuchy.

427390HP

Great, thank you!

Since I do the parts hunting and my brother does the installation, I'll let him figure out the engine side port routing.

I didn't think of going the other way with the bore size, i.e., 7/8 to 3/4. I just knew we didn't want to go from 7/8 to 1. I'll investigate that option a bit more.

Thanks again!

toddalin

If you wanted to "future-proof" yourself with the intent of one day changing the fronts to disks, you can find several M/Cs for a disk/drum (or even disk/disk) set-up and just place a 10# residual valve on the line to the front drums (front and rear if using a disk/disk M/C). If you later change to front (full) disks, you would just remove the residual valve(s).

davekp78

You also might have a hood clearance issue with the dual master on a '63.

dplotkin

Just keep in mind that the relationship between master bore size, wheel cylinder bore size and pedal lever attachment point are critical. The smaller the master bore the less effort required to apply but the longer the travel. The reverse is true, bigger master bore, more effort, less travel. When doing conversions on old cars especially with disparate components it is very important to do the math.

Dan

427390HP

Excellent tip! After all of my research, that option had not been mentioned. Thank you!

I understand that just a dual M/C will fit without issue. Fitment becomes a problem if a booster is added. Will keep an eye out for clearance issues. Thanks!

Dan, I'm acutely aware of the correct combination needed or problems will arise. We first discovered that when we put aftermarket wheel cylinders on my '60 and have a different pedal feel and I also read numerous problems in the research for my brother's '63. I read so much it became mind numbing and that's why I finally created this thread so we don't end up overlooking anything and have a resulting problem. Your advice is greatly appreciated!

silver837

If the M/C on the car is original it has value.