I am working on a hydroboost swap on a 68 f250 Highboy. I believe the hydroboost would work on other applications 67- 72 but I do not know the different pedal combinations.

So the saga of brakes started before I bought the truck. The PO installed 79 f250 Dana 60s and an eBay quality brake booster conversion. The brakes were not great when I got it. The first thing I did was put a 79 master cylinder on the truck which helped but did not fix the brakes. I could still not lock the tires up and I still had too much pedal travel. The rear brakes were adjust to the point they dragged just to verify they were not my pedal travel problem.

Well one day while driving I thought maybe I am just not pressing the pedal hard enough....


So after fixing the pedal rod without using cheap eBay crap I disassembled the front brakes. The 79 Dana 60 has large dual piston calipers that slide. The calipers had been shimmed so they didn't slide and were wearing the pads at a angle... So tore them apart and replaced the pads and assembled them so they moved properly. Well this made my brake pedal travel problem much worse.

Next, I​​​​ started looking at master cylinder size. I looked through rockAuto and compared the ratio of master cylinder bore to caliper and wheel cylinders.

​​​​​​(2 x caliper position area +2 x wheel cylinders)/(master cylinder bore)

I found my ratio was low compared to SUVs and really low compared to 3/4 ton and up newer trucks. My comparison is by no means in depth brake math but it pointed me in the right direction.

I have a j10 with 79 Dana 60s and is has a 1-1/4 master and if they rear drums are out of adjustment it has a mushy pedal. So I decided to go with a 1-3/8 bore master for the 68.



This fixed my pedal travel but I did not have enough assist with the small single booster. So I started looking into a bigger booster but I do not have much space. I ordered one of the aftermarket booster cantilever brackets. After modifying a Dodge Ram booster to fit I did the math on the pedal ratio I would have. Original ratio is 6:1-7:1 and with the booster bracket it would be 3.2ish:1... Not great a newer superduty has a 5:1 ratio.
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After deciding the aftermarket ratio would not work I also decided that I would have to build a new bracket with bushings because the aftermarket steel on steel cantilever was not up to snuff.

That is when I decided the best option for brakes was to "keep it simple stupid". So hydroboost it is.

I ended up finding a cheap booster with a master cylinder for 03-07 Chevy 2500. To bad they packed it poorly and the pedal rod was removed forcefully during shipping.


​​​​I took a partial refund so I could use it for set up.

 

Booster setup. Rod length is perfect for stock pedal location so far. I will probably build a spacer because I would like to lower my pedal some.


​​​​​So far I have just modified the stock mount plate. I will get some shots of the rod length.

 

Got some work done on my hydro-boost set up. Pedal is in stock position with hardly any additional work. I did have to open the hole in the firewall for the booster rod a little but not much. I will build a spacer to move the hydroboost out because I want to lower the pedal 1-2 inches.

Welded the original holes in the mount plate up and drill new holes. The two lower holes are close. I may buy socket head bolts for them.


​​​​​i had to file down a plastic bushing I had from the eBay kit I bought to fit in the end of the pedal. The booster being damaged sucked but has made set up a little easier.


Rod reinstalled (remember by booster is broken but it holds the rod in the right spot) and bolted to pedal. Pedal is in perfect location if stock pedal height is desired.






Shotnof the booster with master cylinder on. I also got started on the lines for the hydroboost.




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This is a measurement from the second hydroboost I bought that came broken. I am sending this one back... I ordered a new brand new hydroboost and master cylinder so this hopefully this doesn't happen a third time. One benefit is this booster is for a 07-11 Chevy 2500 and looks exactly the same.

 

Interesting thread. Once you go for a test drive you'll have to tell us how much change you got once you "stopped on a dime".

 

I have to ask. Why did you set it up for the hoses to go to the top? I have the same set-up and mine are on the bottom.

 

Haha, good one
I may run with the fitting downs but will have to change the return line fitting to a 90 because it is pointed right into the cam cover if it is turned 180. I will probably have it whatever way gives me more clearance. I have not welded a tap to clock it yet.

 

Well I made some progress. I am currently waiting on fittings because the master cylinder I am using is designed for 1/4" line so a flares 3/16 line does not mate up correctly. All the lines are ready for when I get the fitting.

I ran the hydroboost with the fitting up because turned 180 degrees the hydroboost would hit the steering column's mount plate.

I made a bracket to hold the lines and the rear brake bias adjuster. I may tweak one of the lower lines where it meets the flexible hose still but have not decided for sure. I also haven't decided off I want a bracket supporting the steel lines where they meet the flexible hose at the bottom.

This has been a good amount of work but I do enjoy bending lines.

Pictures:

Bending some lines to match the wire and determining where to make a bend.



picture of the difference in master cylinder. If you use the correct 03-07 Chevy 2500(base model) master cylinder it is set up for 3/16 line but I got a 03-07 with tow package OEM brand new master for 60 bucks so I will make it work.


Brake lines and hydroboost lines as it sits:





brake controller. I found an brand new old hydraulic style brake controller for much less than the electric ones. My experience with electric brake controllers has been that they suck if it is not an OEM integrated controller. So I am betting the hydraulic will be better than the newer electronic ones.


Hopefully next weekend I will be driving the truck again and can report how the brakes work.

 

I was thinking about getting a hydroboost setup from a 99-04 mustang. Any thoughts?

 

It would probably work well. You will want to compare master cylinder bore and pedal rod length to your current set up.

 

Where did you get the hardline? is that 3/8"? ....looks great!

 

Thanks!
The hard line is 3/8 stainless that comes in 6ft lengths and I got it on Zoro. It's a industrial supply company. I like that the line has ratings and specs on it. The fitting and hydraulic hose came from discounthydraulichose.com.

 

Got all the fittings and bled the brakes. I made a vacuum bleeder after getting tired of bleeding my brakes like crazy. With the vacuum set up I pull a vacuum and use it to draw the brake fluid it. I then pull a vacuum again and pump the brakes a few times. Draw in more brake fluid until the master cylinder reservoir is full and brakes are bleed.

If it doesn't hold a vacuum I then pressurize it and use soapy water to find the leak.






The brakes work really well. If anything they are on the touchy side but stop the truck really well. I may try to reduce the pedal leverage when I lower the pedal some.

 

Looking to do hydroboost...

Why the cheby unit instead of a 99+ superdoody or other? price/availability/fittings?

What type of hoses did you get? are they male flare/AN? I like the hard lines, but any reason to not just use hose the whole length?

What brakes are you running on rear? disc or drum? If drum do you run a residual valve? Assume that master is disc/disc?

Sorry for so many questions
Thanks!

 

I went withe the Chevy because the rod length. I think the basic internals are same across most brands. Using a unit with a longer shaft and an adapter would make the install and removal easier.

I used AN fittings. No reason for hard lines other than I enjoy bending hard lines...

I ended up adding a 3/8" spacer between the booster and firewall to lower my brake pedal. Without the spacer the pedal is at the stock location.

you have a lot of tire to stop. I would probably match the booster and master cylinder that matches your axles.

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