73 Master cylinder direct replacment please help

[kemmer]

I have been looking for a brake master cylinder replacement. Can some of you point me to a good aftermarket one?
Or tell me where I can get a good core. mine is pited I cant rebuild it. I would like it as close to stock as I can get.

[Byron510]

Man, this has been an issue.
For the last 10 years, we have been faced with supply only of Chinese made units of completely different design. The issue is that the rubber quality is shite, and they don’t last. The same goes for the clutch hydraulic parts. The problem is that the bore sizes are not original so OEM rubber parts cannot be installed. The 510 should have a 3/4” bore size, but the one I took apart a few weeks ago had an 18mm bore.
I don’t know what the solution is, and it’s agreed we need to find a quality solution.
For now there are units available that bolt in, but the longevity is suspect for sure. The units lasted 35 plus years in some cases, you’d be lucky to get 5 out of the Chinese ones we buy today because the rubber parts just turn to mush!

Byron.

[edekalil]

Yes when I got my cars going a few years ago I had to get some from O'reilly's auto parts, I'm sure it won't last as long as ones from the past but they said it was life time guarantee. So I guess you'll spend your life changing it regularly every so often. At least I got all the cars going and stopping now.

[andrewm]

I most recently got a 7/8 master for my 510 from Lordco!

[icehouse]

The thing I hate is the fact that you can't get a master where the push rod is retained. Which requires you to settle for a master ment for a car with a booster. I take them apart shave down the piston so I can install the push rod and retainer.

[Byron510]

Jeff, I have done the same for a few local guys, but I’m pretty much out of stock BMC and Clutch MC push rods now. Time to start machining them I guess.
I also modify the washer from the stock MC’s to fit the usually smaller bore of the Chinese units, which seem to average 18mm, for the 510’s 3/4” replacements.

Pain in the butt - for everyone.

Byron

[datzenmike]

The 610 and the B-210 both use the same 3/4" BMC... though not the same as the 510. The 710 through '75, the 620 truck through '75 and the '77-'79 S10 200sx all use slightly different dual 3/4" masters.