# 1966 master cylinder differences



## Duff (Jan 12, 2020)

Other than the push rod length, are there any other differences between a power drum master cylinder compared to a manual one, on a 66 GTO?


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## Duff (Jan 12, 2020)

I've been doing some more research and I think I have it figured out, manual drums have the port on front and 1" bore, power drums also have 1" bore and most of them have the side port and a bleeder. I'm digging thru some cores that I have for rebuilding.


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## GTOJUNIOR (Aug 7, 2011)

IIRC the PB is a 7/8" bore and MP 1"


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## Duff (Jan 12, 2020)

I'll have to check on that, my cores all have 1" bores, one of them is from an original PB car, still has the booster attached, it could've been changed over the years though. The casting #'s I have are 5464293 and 5464343 all have the Delco logo cast into them. I'm wanting to get an original / correct MC and the wheel cylinders SS sleeved/rebuilt.


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