To try to bring together another thread on CMP Chev master cylinders
http://www.mapleleafup.net/forums/sh...aster+cylinder
This is rapidly becoming one of the "the more you study, the more you realize you don't know" things.
I recently pulled out a couple of master cylinders (all 1-1/4") thinking I would send them for sleeving to be "ready when needed". It turned out I had 4 master cylinders sitting. 1 side mount and 3 base mount. The side mount shows part number 5300918 (crosses to Wagner FD-4194). All base mount seem similar in sizing but were not measured with any precision tooling. One has number 0260 cast in the side and it looks as if there were other digits that were supposed to be there. Possibly the whole number 5450260 as in the C15A parts book? The other two have 5450261 cast in. The end caps for the base mount cylinders were all hexagonal to take a wrench but the one for the side mount was round and ribbed. Although they are all 1-1/4 bore, the end caps from the base mount exchange with each other but there's no way the one from the side mount can be threaded into a base mount cylinder (too large). I've no idea why Delco would have done that. The Chevrolet Master Parts Catalog 1929-1948 makes reference to several 1-1/4" master cylinders with different part numbers for the assemblies (not matching any of the numbers above) but all seem to use casting number 5450259 as a starting point. it is not clear if this is a side mount or base mount part.