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Discussion Starter #1
Had a problem with a leaking master cylinder. My car 1966 has non power front disc rear drums. The cylinder I ordered was a Delco 18m1878. The problem that I am having is that the old cylinders valve my plunger would fit at least 2inches inside while the new cylinders valve is right on the edge. Also it was hard while trying to bench bleeding the new cylinder. Both look like they have the same size valve. My question is do you think the only thing to do is to get a shorter plunger because the one I have will not fit on the top hole of the brake peddle and barely fit on the bottom hole. Thanks for any help.
 

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When you say "plunger" ; you're referring to the rod from the pedal to master cyl?
There is some adjustment on that rod if you haven't already tried that.I rememver having to cut some off the rod to get the fit right.
Make sure the rod is seated well into the pocket of the m/c; there should be just a slight amount of play when the pedal is fully relaased and no chance that it will fall out.
 

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Discussion Starter #3
That's what I am talking about. I adjusted it and it barely fits into the bottom hole in the brake peddle which i believe should be the location of the power brakes. I believe I have the wrong master cylinder.
 

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You definitely have the wrong master cylinder.

All manual brake master cylinders should have the deep cup. That's what the pushrod is designed for, and the deep cup assures that the pushrod won't fall off the master cylinder's plunger.
 

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is it possible to rebuild yours that has a leak ?
 

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Discussion Starter #8
Thanks for all the answers. Checking on new ones only coat 50 bucks not so bad. Just a PITA to deal with all the lines and brake fluid.

Thanks again.
 

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The master cylinder you're trying to use is for power brakes (shallow pushrod cup), and it has a 1-1/8" bore. You need a 1" bore master cylinder for non-power brakes.

There are two that will work. First is a master cylinder for a 67 Nova. It will be 1" bore, a deep cup, and have two small fluid reservoirs. Second is a master cylinder for a 68-76 Corvette with manual brakes. It will be 1" bore, deep cup, and it will have two large fluid reservoirs. The main difference here is that the Corvette m/c will be quite a bit longer and that may cause interference issues with other things under the hood.

Normally you'd want a big reservoir for disc brakes. The reason is the fluid level will drop as the pads wear, and the big reservoir won't have to be topped off through the life of a brake pad. With the small reservoir you'll have to top off the fluid as the pads wear - really no big deal. Just check the level a couple of times a year, which you should do anyway. Having a big reservoir with drum brakes is not a problem at all.

I've run the 67 master cylinder on mine for many years with a disc/drum setup.
 
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