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Old 08-12-2019, 12:19 PM
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TheBandit TheBandit is offline
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Join Date: Jan 2006
Location: Ventura County CA
Posts: 4,654
I've been working on the brakes off and on and making progress. It was finally time to take out the old master/booster combo.

I took a few measurements on the existing line locations to get a relative starting point for new lines down the road. I plan to reuse the original distribution block and warning switch, so knowing the relative location of the distribution block should be sufficient for planning out the new lines.

Here is the original single 11" diaphragm booster and the new dual 9" booster. The booster is a Tuff Stuff 2229NC originally for a C3 Corvette. I am using DSE low angle mounting brackets.

I started by measuring the clevis length on the original booster relative to the firewall mounting surface.

I bought a universal 3/8-24 clevis extension which of course needed to be cut down to achieve the right length. The bandsaw made quick work of that.

I had read about folks needing to clearance the firewall hole for this booster. Sure enough the bellows on the input rod measures about 2" diameter while the firewall hole measures only 1-3/4". This bellows is not intended to seal on the firewall - in the original C3 application, there is a seal right up against the booster and the bellows is just under the dash area. Using this in my Nova, I don't think there's a good way to make it seal without potentially interfering with the pushrod movement. I'd rather not chance the brakes hanging up, so I have decided I am willing to leave this area unsealed.

Here's the booster loosely in place to show there's no way the bellows would fit through the firewall hole unmodified.

I decided to open the hole to 2" diameter. I picked up a special mandrel that holes two holesaws at once so the smaller can be used to pilot the larger one. This worked extremely well! The mandrel is part of the Bosch HE1 hole enlarger kit.

Unfortunately even after enlarging to 2" there was still interference with the bellows at the bottom of the hole, which you can see below from the inside of the cabin.

So I marked the hole and used a carbide cutter to enlarge it at the bottom by about 1/4", which provided adequate clearance.

Here are the master and booster now installed in their new home. I'm happy to report good clearance all around using the low angle DSE mounting brackets.


Ongoing 70 Nova build:
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