Smaller Brake Booster

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Smaller Brake Booster

Post by sportster_restorer on Sun Jul 26, 2015 11:47 am

I'm looking to run a smaller brake booster to save some weight and clean the engine compartment a bit. Anyone doign something like this? If so, what donor car did you use to get a smaller booster?

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Re: Smaller Brake Booster

Post by brownbomber77 on Sun Jul 26, 2015 2:18 pm

Trams Am used a dual brake booster that is much smaller in diameter

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Re: Smaller Brake Booster

Post by dynchel on Sun Jul 26, 2015 3:51 pm

Mine has no booster. Just a master cylinder bolted to the fire wall.
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Re: Smaller Brake Booster

Post by thatfnthing on Mon Jul 27, 2015 10:20 am

I swapped mine to the booster and m/c from a 93 Caprice, primarily for mating it to the ABS system, but the booster is smaller than the original G3 one.  The real weight savings, though, is in the 2 lb aluminum-and-plastic m/c versus the old 10 lb cast iron one.
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Re: Smaller Brake Booster

Post by bitterfitter on Fri Jan 06, 2017 11:52 am

Thatfnthing- Did you have any issues with running the smaller booster for your brakes over the larger one? Also did the '93 Caprice one bolt up without any modifications?

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Re: Smaller Brake Booster

Post by thatfnthing on Fri Jan 06, 2017 12:23 pm

I'm not sure it's actually smaller volume-wise. It's smaller in diameter, yes, but it's actually much "thicker" (for lack of a better term). So total volume may be the same or even more. Don't have any specs on either, though.

I still need to address the rear brakes, so my total braking is not where I'd like it yet, but I swapped the Caprice booster/master assembly mainly because I had way too much pedal travel using the Monte assembly after doing the rest of the ABS system. I personally suspect the modulator requires more fluid volume. So it seemed to me that since the parts were all designed to work together, I'd be best off using the Caprice unit. Plus the Caprice unit was a lot less weight.

The main difference is that in the Caprice the assembly is bolted directly to the firewall, while it's on a standoff in the Monte. However, if I widened out a couple of the holes on the standoff, the Caprice assembly will mount. The potential issues left are then:

o Hood clearance: The Caprice booster projects farther than the Monte booster, so the reservoir is farther up and forward from the original position, and it just touches the my hood insulation when I close it. The Chevelle may or may not have this issue, but check before you slam the hood the first time. Smile If you have a belt or disc sander, you should be able to change the angle of the standoff a few degrees to lower the reservoir.

o Pedal rod length. The Caprice push rod will be too short. Rather than try to disassemble the Caprice booster to swap in the Monte's push rod (which I suspected would be too short also), I made the whole thing adjustable -- I cut the end off the Caprice rod and threaded it, then did the same to the Monte's pedal rod. Since they're the same diameter, I simply joined them with a threaded coupler (3/8" IIRC) -- now it's adjustable for total travel length.

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Re: Smaller Brake Booster

Post by Hs1973 on Fri Jan 06, 2017 12:28 pm

I bought a tuff stuff 9 inch dual diafram booster. It works great and is smaller than the original 11 inch one. And due to the dual diafram it has just as much boost as the original. Only catch was i needed to make my own brackets to mount it. But that was a 2 hour deal, so it was not that bad.
I have heard that some mounts the Hydro setup from an astro van wich is much smaller and should give crazy stopping power. Ive seen a couple of setups on trans ams, and it look like a mastercylinder just boltet to the firewall. And it gives more room and weight sawings than a small booster, plus the better brakes. I thought about doing a Swap myself.
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Re: Smaller Brake Booster

Post by bitterfitter on Fri Jan 06, 2017 12:32 pm

Thanks for all the info. I like the weight savings idea. I wonder if the newer plastic master cylinder would work with the original type booster? Did they change threads in the hydraulic fittings from SAE to Metric during this time period?

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Re: Smaller Brake Booster

Post by thatfnthing on Fri Jan 06, 2017 12:35 pm

That I can tell you won't fly, 'cuz I was going to try that.  The diameter of the m/c bore on the Caprice unit is much larger than the mating socket on the G3 booster.

Fittings -- oops, I forgot that part. Sorry, undercaffeinated. Yes, the fittings will be metric (6mm IIRC), but the m/c also will require a bubble-flared end instead of the traditional inverted flare. You can use the traditional brake line, but the fitting will need to be metric -- if memory serves, the 6mm fittings were a bit tight.
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Re: Smaller Brake Booster

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