Re: {FORGED?} Re: more brake booster

[farna@xxxxxxx]

I'm sure Tom will verify this: the master cylinder will physically bolt up with no problems. You might have to adjust the rod from the booster to MC, results vary (and some boosters don't have an adjustable rod). Most people don't have to touch the rod. The only difference is the connections on the brake lines -- they are sometimes different between drum and disc brakes. The master cylinders are virtually the same for small car drum and discs from 1977-83 -- all with the 2.6" piston caliper. Just pull the residual pressure valve from the front brake outlet on the MC and check the fluid once a year. The large reservoir on disc brake MCs is an attempt to dummy proof the system -- there's enough fluid in there to last the life of the pads if you have no leaks and never check the fluid! Front brakes are more important than rear, the engineers weren't as concerned about the rear drums. 

71-76 cars all use big piston (2.75" Kelsey Hayes or 3.1" Bendix) calipers that use a bigger bore MC. Don't mix the calipers and MCs! The 3.1" calipers require a 1-1/8" bore (depending on car size), 2.6" a 1" bore. The 2.75" K-H brakes used a 1" bore for power discs in small cars, 1-1/16" bore with non-power discs (I don't think non-power discs were available in the big cars), and 1-1/8" bore in big cars with power discs. 1" bore was used in all-drum cars, all models, power or manual, all years. If in doubt as to what you have pull a caliper and measure the piston. Mid 70s K-H may have used a 3.1" piston as well, I don't have all my books with me right now (having my morning coffee at work!). The late 80s AMC cars used a 0.988" MC (not exact, but do remember it's just a small amount less, likely a close metric dimension), but that's "close enough" to 1" to work well.

Looks like it's about time to run an updated brake article in AIM. I've since uncovered the mystery behind combo valve useage with the help of Jeff Reeves and his 79 TSM (one of three years I don't have from 55-83, not counting all the separate American TSMs... I only have 58, 61, 62, 64, and 67 American volumes, 68-69 don't have separate TSMs, so everything is pretty much covered with the five).


On October 31, 2005 Mr. AMC wrote:

> Tom what did you do to mount a disc master to a drum booster? I was told it would not fit. I have a 79 Concord disc brake set up on my yellow 74 Hornet with the stock 74 drum booster & master and it works fine. It requires a touch more pedal pressure than my orange 74 Hornet with the factory power disc brakes.
> "Doc"


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