New Power Booster and MC Question - Impala Tech
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post #1 of 2 (permalink) Old 04-11-2016, 09:52 PM Thread Starter
Join Date: Nov 2015
Location: NJ
Posts: 27
New Power Booster and MC Question

I installed a new power booster and master cylinder tonight. When I went to install the master cylinder, the rod for the booster was protruding a couple of inches meaning the piston in the MC had to compress quite a bit in order to get the nuts onto the studs. I don't recall having to do this on other cars, but it's been a really long time since I've had to install a new MC. I checked the old power booster and the rod stuck out the same distance. Checked the old MC and it was identical to the new one. Is this okay? Will the booster contract somehow when vacuum is applied? I'm only half way through the job. I'm going from a single-reservoir to a dual-reservoir. I need to install the new lines tomorrow night and then I'll know what I'm dealing with. But I don't want to put fluid in the thing if there's something wrong.
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post #2 of 2 (permalink) Old 04-16-2016, 08:25 PM Thread Starter
Join Date: Nov 2015
Location: NJ
Posts: 27
Okay so the answer is that the MC is wrong. Ecklers sold it to me as a "55 to 72 Power Brake Master Cylinder, 4-wheel Drum". The reason I bought it was because the instructions in their dual-reservoir MC kit say that the difference between a power master cylinder and manual master cylinder is that the manual has a hole for the pedal rod and a smaller diameter piston. The power does not have these things.

Guess what? That's not true - at least through '67 (which is far as I looked). My '64, with factory power brakes uses a manual master cylinder (with the hole and smaller bore cylinder). So does '65, '66 and '67. In '67 they went to a dual reservoir master cylinder. I spent all day bending lines and installing a distribution block for the dual-reservoir conversion only to find the MC was wrong when I went to bleed the system (no pedal travel because the piston was already bottomed out).

Oddly enough, Autozone has a '67 master cylinder in stock that looks like it will work. I'm going to try again tomorrow....
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