I need to replace my master cylinder (round single cylinder manual 4 drum) gasket / diaphragm. I have exhausted the local auto parts stores and of the 6 - 7 resto parts catalogs I have - nobody carries it. '64 - '66 take the same gasket. Ground Up has the round lid listed as only for '64 - '65 and doesn't carry the gasket, Their tech said he never heard or seen a '66 factory 396 with just a single cylinder - most I've seen has one.
Any sources would be appreciated.
You might check Zip products www.zip-corvette.com They carry Corvette parts, and you can look in their catalog & see if any of those lids might work on your Chevelle.
Use the 56~82 catalog,Brakes,Master cylinders. It has pics of the caps & gaskets.
BL
