Question on a componet

Josh Shoemaker

Josh Shoemaker

Member
I have a question about a braking componet that is installed on my Scout. This is a 1961 80 and I am trying to identify what this is. I think it had something to do with the brakes at one time but it seems that it was disconnected. Is there anybody on here that can indentify/explain what this device is supposed to do?

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A bleeder and line that has been cut and soldered closed.

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The other end of the hose. I assume that this is a vaccum line????

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The brake line on the previous picture goes back to the master cylinder. But is disconnected

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That is a bendix "hydrovac" unit, a precursor to the more commonly used (and much cheeeeper) "pancake"-type vacuum booster most of ya are familiar with. That is the version with an integrated air filter.

These are real common on ihc-produced fullsize rigs of that era, kinda unusual to find one on a Scout 80 though, they don't hardly need a power brake system in oem form!

Ihc also used another variation referred to as "master-vac" which is similar but uses a different type master cylinder.

That one uses the "output" of the brake master cylinder to input pressure/flow to the "slave" cylinder mounted on the unit. Yours has been disco'd and plugged off. The "output" from the slave then went to the brake system junction block for hydraulic pressure distribution to the front and rear brake systems.

An advantage to these items is that they could be remotely-mounted....many are found bolted to the frame rail underneath the cab.

Here's a decent write-up I filed away some time ago for future use if I'm ever faced with doing one of these:

bendix hydrovac system overhaul -- a stovebolt tech tip

These units are also covered of course in several versions of the ihc-produced shop manuals.
 
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Thanks for the reply michael, is this something that should be reconnected? I assumed there was a problem, that is why is was dissconnected to begin with. Or someone like me was working on it and didn't know what it was doing in the circuit and just cut it out of the way.

And would it be worth the trouble to connect it back to the system for the advantage (if any) of having it? Or is it just as good to have it setup without it.
 
If ya determine that that hydrovac was actually an oem or dealer-install item, then it might be worth bringing to life if you are doing a complete restoration.

Otherwise, I'd put it on the shelf for use at some point in a scavenger hunt.

I just edited my first reply to your question, check out the link in that edit. I have torn one of these down years ago...I personally see no future in dealing with 'em unless you are going for a major restoration and this unit was original. I find no reference to those being used oem on the s80 platform...but a dealer-install was certainly possible!

Depending upon which brake set your s80 has...the "option", 10" lockheed fronts and 11" bendix rear combo is plenty stoppers for a stock s80...even with somewhat larger tires (no greater than 32"). That is not a power brake set.

All depends upon what your ultimate use for this rig is gonna be.
 
I have ordered a line set ticket for it but it has not came in yet.

I will have to see if it was ordered with it or not. I will check that link out. Thanks.
 
josh shoemaker said:
I have ordered a line set ticket for it but it has not came in yet.

I will have to see if it was ordered with it or not. I will check that link out. Thanks.
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I have all the latest parts lists and manuals for the s80 and s800, no mention of a hydrovac being used on those platforms.

I also have copies of several parts and accessory catalogs that have every item avaialble for every IH-produced motor truck, from s80 thru the class 8 coe stuff, no mention of a "dealer install" hydrovac kit.

But, it would be perfectly reasonable that a dealer (or an individual) could have installed that unit, much simpler than trying to install a pancake booster along with it's companion master cylinder (there is no space for that in the s80 firewall hole!!). And the hydrovac is a fairly simple "add-on" since you retain the oem master cylinder and just plumb it in, something like adding on oldskool trailer brake controller.
 
Correct me if I'm wrong but boosters were developed due to the disk brake systems requiring much higher line pressure than drum brakes.

As we all know the 80 had drums. Don't see how the booster would help once the shoe servo action began to take effect. It would just lock up the wheel. I know the 61 first generation did not have servo action drum brakes but 62 did as an option. 10" iirc.
 
Robert kenney said:
correct me if I'm wrong but boosters were developed due to the disk brake systems requiring much higher line pressure than drum brakes.

As we all know the 80 had drums. Don't see how the booster would help once the shoe servo action began to take effect. It would just lock up the wheel. I know the 61 first generation did not have servo action drum brakes but 62 did as an option. 10" iirc.
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Naw man..."boosted" brakes go way back in time! And I'm talkin' plain old "servo-action" drums on passenger vehicles too.

GM started crankin' out booster stuff around '53. Same for others. The eurotrash stuff saw a form of power brakes in the 20's.

Check the packard system:

popular science - google books

Ihc intro'd the hydrovac system with the "a" series light truck stuff (m/y 1957), though it might have been used on some other versions before that.

The first production euroweenie disc brake stuff on the u.s. Export versions was not boosted, that was maybe '62 onna mga?? Or coulda been the mgb, I can't remeber that detail.
 
Robert kenney said:
correct me if I'm wrong but boosters were developed due to the disk brake systems requiring much higher line pressure than drum brakes.

As we all know the 80 had drums. Don't see how the booster would help once the shoe servo action began to take effect. It would just lock up the wheel. I know the 61 first generation did not have servo action drum brakes but 62 did as an option. 10" iirc.
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Power brake boosters came with the first power brake systems --( which were all drum in america). Cannot remember the year GM / Ford / chrylser introduced power brakes...

Us auto manufacturers seemed to be very reluctant to introduce disc brakes -- probably because europe (bosch? / girling?) held the patents and they would have to pay fees.

Us car brakes in the 50's were very inadequate for heavy use -- probably because the engineers sat in an office in detroit. The brakes on early muscle cars were nothing to shout about.

From a 1972 road test mag -- it shows power brakes were not available for the Scout 800, but were available for the t/a and pickup.

Similiar to the us adoption of steel belted radial tires -- firestone "created" a tire with a 2 inch steel belt in the middle of the tread and called it a steel belted radial... Among other things, they probably did not want to get rid of their now outdated tire manufacturing equipment...
 
josh shoemaker said:
I got a another question, from what I can tell; are all the hard brake lines on the 61 Scout 80 3/16 in size?
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If...the oem master cylinder is still present and the rest of the plumbing does not appear to have been altered, then...yes, all brake plumbing was done in 3/16" brake tube with appropriate double flares.

The oem system is a single circuit design, the standard system on motor vehicles of that era.

What bit of balance between the front and rear brake assemblies is achieved through the use of different diameter wheel cylinder pistons front-to-rear.

And keep in mind...the "standard" brake set for the axles is somewhat different in both sourcing and design as compared to the "optional" so-called "heavy duty" brake sets. But the same master cylinder was used and both brake sets used 3/16" plumbing.

There was only one front axle available oem in the 4x4 option rig, that's a spicer 27...the standard rear axle was also a spicer 27. The "option" rear axle was a spicer 44, with the tapered, two-piece hub and and axle shaft. And a Scout 80 spicer 44 would have had an "offset" center section, that means the driver side axle tube is about 2" longer than the passenger side.
 
I remember the brake pedal on my Dad's 54 olds f88 having the words "power brakes" molded into the rubber. It also was an automatic, but had "armstrong" steering.

Lyle
 
lyle wiese said:
I remember the brake pedal on my Dad's 54 olds f88 having the words "power brakes" molded into the rubber. It also was an automatic, but had "armstrong" steering.

Lyle
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And not just any old slushbox dude,...it was a "hydramatic" no doubt! That's the tranny that put B&M in the bizz way back in the early 60's when those boyz developed the original "hydro-stick" beefed up unit for drag racing.

That guy I was telling you about we met at the santiam rest stop on the way to the bee last summer (hugh tucker) was their original production engineer when they went into the bizz full time. In fact, he said he retired from B&M and that was not too many years ago!

Check this link to hugh's stuff:

hugh tucker : ventura motors
 
michael mayben said:
if...the oem master cylinder is still present and the rest of the plumbing does not appear to have been altered, then...yes, all brake plumbing was done in 3/16" brake tube with appropriate double flares.

The oem system is a single circuit design, the standard system on motor vehicles of that era.

What bit of balance between the front and rear brake assemblies is achieved through the use of different diameter wheel cylinder pistons front-to-rear.

And keep in mind...the "standard" brake set for the axles is somewhat different in both sourcing and design as compared to the "optional" so-called "heavy duty" brake sets. But the same master cylinder was used and both brake sets used 3/16" plumbing.

There was only one front axle available oem in the 4x4 option rig, that's a spicer 27...the standard rear axle was also a spicer 27. The "option" rear axle was a spicer 44, with the tapered, two-piece hub and and axle shaft. And a Scout 80 spicer 44 would have had an "offset" center section, that means the driver side axle tube is about 2" longer than the passenger side.
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That's what I was thinking, just wanted to be sure.

Thanks michael.
 
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