'64 Brake MC/Booster Question

["Terry Town" <terrytown@xxxx>]

I'm confused and hoping someone can help me out. I have a '64 300 Sport with a 383 and power brakes. I need a new brake master cylinder, so the local NAPA sells me one. NAPA part # 10-36706, it looks very similar to the existing one, but has an additional downward pointing outlet just under the regular horizontally pointing outlet. The second outlet is capped off with a plug, so I figure that the unit will still work fine. When I got the old master cylinder off I compared the two. The NAPA one has a casting number on the bottom of the unit of 2265634. My old one has a casting # of 2265633. Hmmmm. I then noticed that the receptacle depths for the pushrod in the back of the MC piston are different between the two MCs. The NAPA one is about .95" deep and my old one is 1.25" deep. I thought that maybe it's as simple as adjusting my pushrod shorter, so it doesn't stick out as much from the power booster unit. I looked in the factory service manual for adjustment info and here is where I got really confused. My power booster visually appears to be a Bendix Dual Diaphragm type, and the FSM clearly states that these are for Imperials only. (It also says to NOT adjust the pushrod)

Did 300 Sports come with the Bendix dual diaphragm unit? If so, does anybody know a NAPA part # for the proper MC to use with this booster unit? Or do I need to just adjust the pushrod in about .3"?

If the booster unit isn't the proper one for the car, I'd like to replace it with the proper one. Any thoughts on where these might be available, part numbers (NAPA or otherwise) to ask for, etc.

Any help from the group would be appreciated.

Thanks,
Terry Lynch
St. Petersburg, FL

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