67 Brake Fluid Flush

[Joe L.]

Exactly. I'm not sure of the wall thickness of a sleeve, but if it's anything like a caliper, the same bolt would likely be long enough assuming of course one decides to do it the right way.

Thomas-----


The original stop screw would definitely be long enough even with the sleeve. However, this is an odd configuration screw and there might not be enough threads for it once the master cylinder was sleeved. However, the correct size hole could be drilled through the sleeve and threaded, if necessary. I think rebuilders want to avoid all this effort.

[Thomas S.]

Final conclusion is that the MC that was in the car was not correct for 67 based on the appearance of numbers on one of the outlet ports. There are only 3 numbers visible with no good evidence of a 4th.

Lonestar confirmed that the one purchased was an original core rebuilt with a SS sleeve. They also correctly drilled through the sleeve installed the stop screw. No numbers on either port and it has the correct DC stamp on the front top machined area. There are some casting numbers on the inside of the Lonestar mounting flange (hidden once installed), but none on the one that came off the car. I didn't take a picture of those numbers.

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[Thomas S.]

Master cylinder from LoneStar is in and no surprises. Used the GM OEM tool (J22489) works perfectly. I picked one up on eBay. Its roughly 3/8" solid steel and has a cork gasket that matches the master cylinder perimeter, no overlap. Uses a chain and is shown on page 5-4, 67 in the 67 Chevy service manual.

I was able to pressurize the fluid to 10-pounds, which is the spec in the book for Corvette, and absolutely no leak down or fluid leaks. I think the key here is the rigidity of the plate compared to the universal aftermarket versions. The original gasket was glazed so I replaced it with the same cork type cut to match the original.

File under the domino effect. As is typical for any old car project, during the replacement of the all the wheel bleeders, the inboard left rear had been loctited in. Why? Because the caliber threads were stripped. It was discovered during the pressure bleed which is better than finding out on the road.

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[Thomas S.]

Update to my previous post on leaking bleeder valve. I realize that the seat of the bleeder is what seals, so in my case that is likely the issue or perhaps some debris. That leak may or may not have been masked by using the sealants on the threads.