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Old 06-20-2026, 12:13 PM
Mark66 Mark66 is offline
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Location: Houston, Texas
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Default 1966 GP power brake and MC upgrade

I own a 1966 Pontiac Grand Prix with a factory console 4 speed with 8 lug drums. The original power brake unit and original (single chamber) master brake cylinder are dying. I would like to upgrade to the Master Power Brakes preassembled power booster/ dual chamber master cylinder unit (BM17015) designed for power drum brakes.

Has anyone had specific experience installing this unit on a big 1966 Pontiac with a factory 4 speed? There seems to be enough space to install the MPB assembly – the headache will be to try to retain the existing distribution block/lines for the front brakes and bend the existing rear brake line to connect to the new master cylinder. I would block off the rear port in the existing distribution line and use flare nuts to connect the old rear brake line to the new master cylinder line (maybe using a brake light pressure switch connector). I could of course buy news brake lines. And I do not think that I will need a proportioning valve.

Are there any installation lessons that I can benefit from?

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Old 06-20-2026, 09:20 PM
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stevep stevep is offline
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Your original booster will work, if it was good and you would need a 67-68 master that would fit the Delco or Bendix booster.

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Old 06-30-2026, 01:49 PM
66_Cat_Jon 66_Cat_Jon is offline
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Default I did the Master Power power brakes with front disks conversion on my auto trans 66

So there's quite a few differences, but some things still apply. What I would suggest for the lines is that you just scrap the original short line that went from the master cylinder to the dist block. Leave the front brake lines attached to the block as you said. Measure approximately how long of new lines you need to go from your new cylinder front brake port to the dist block and from your new cylinder rear brake port to your now disconnected feed line to the rear. Buy the closest (but not shorter) lengths of pre-made Nickel Copper lines and bend them to fit. The one to the dist block will be pretty simple. For the rear you will have to CAREFULLY bend the original rear feed line up and away from the dist block so you have a little clearance to attach your new line with the appropriate brake line splice fitting. Of course plug the rear outlet of the dist block as you said. The Nickel Copper lines are very easy to work with and resistant to rust. The one thing you should verify with someone more knowledgeable than me is that it's ok to bypass the dist block to the rear because it may be that the block is also functioning as a prop valve.

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