Dan Wheeler's One-Ton 1.5" Bore Master Cylinder and Hydroboost Thread

[DanWheeler]

Hi all, been a while since I've posted a project thread but got some time on my hands these days

Project:
Upgrade to One-Ton 1.5" Bore Master Cylinder

Why:
Current setup is a 1.25" 1995 Astro master cylinder with matching hydroboost. Because of 1-ton brakes with high volume caliper pistons, fluid volume with 1.25" bore master cylinder is too low for adequate braking. (soft/squishy pedal) Using lots of stainless braided AN3 brake hose and 41" tires probably doesn't help.

Note: The F350 master cylinder does not fit the Astro hydroboost. A matching 2008 F350 hydroboost must be used

Parts List:
- 2008 Ford Super Duty Hydrooboost unit (link)
- 2008 Ford Super Duty Master Cylinder (link)
- 10x1mm to -3AN adapter (www.summitracing.com part: ear-592032erl)
- 12x1mm to -3AN adapter (www.summitracing.com part: ear-592053erl)
- Motorcraft Part#: SW6349 (9F924) (link) OR a 3/8-24 brake line plug
- Wilwood prop valve (www.summitracing.com part: wil-260-11179)
- Two (2) 1995 Astro master cylinder reservoir assemblies (split them apart and use the two larger reservoirs)

There are a whole bunch more parts used here but those above are the most important ones to make this work. The stock reservoir is too tall even with 3” body lift so Astro reservoir is required and just happens to fit perfectly on the Super Duty MC.

Some pictures of parts received so far to get things started:

 

[Apogee]

Dan, you may want to consider removing the pressure sensor/switch in the Wilwood distribution block/proportioning valve (260-11179), and replacing it with an 1/8" NPT plug if you're not going to use it for anything. Those pressure transducers can fatigue and split over time, so if you're not using it, there's no reason not to remove that potential failure point.

Just for the purpose of clarity in this thread, when you say you're running 1-ton brakes, you mean Superduty, correct? Earlier 1-ton brakes from the 1970's, 1980's and 1990's have smaller piston areas than the SD stuff.

 

[DanWheeler]

Dan, you may want to consider removing the pressure sensor/switch in the Wilwood distribution block/proportioning valve (260-11179), and replacing it with an 1/8" NPT plug if you're not going to use it for anything. Those pressure transducers can fatigue and split over time, so if you're not using it, there's no reason not to remove that potential failure point.

Just for the purpose of clarity in this thread, when you say you're running 1-ton brakes, you mean Superduty, correct? Earlier 1-ton brakes from the 1970's, 1980's and 1990's have smaller piston areas than the SD stuff.

Thanks for the tip, I'm not sure I'll use that sensor, there's also a similar port on the bottom of the master cylinder that either needs a plug or the stock part used for cruise control cancel. (part # above) It takes a 3/8-24 plug.

As for 1-ton vs Super Duty and year, not sure but my brakes are:

- Front - 89 Ford F350 Dana 60 stock calipers
- Rear - 76/77 Eldorado rear calipers

I must be bored... I collected all the MC and caliper piston specs for these 4 different scenarios to compare the caliper to master cylinder piston ratio:

So my final ratio will be pretty low... lower than what Ford thinks they need for their F350. Meaning a lot of master cylinder piston surface area for every inch of caliper piston surface area. But again, bigger tires and I'm compensating for some mush in the soft lines AND my poor Explorer 5.0 power steering pump is pushing a hydroboost unit, ram assist steering and the power steering rack so it's probably not supplying as much pressure as the h-boost wants. Maybe?

 

[toddz69]

Very timely! I was just mulling over this same topic in my head recently and was going to do some math and do some comparison of factory master cylinder/caliper bore ratios. Looking forward to your results.

Todd Z.

 

[nvrstuk]

It's gonna work great...
how do I know... 'cause I've been thru the same issues with Astrovan mc not having the bore/capacity to fill JD7 calipers (Chevy 3/4ton) front and rear. We figured the surface area compared to what my Astrovan mc was working with before and I was over 2x the surface area.

The front calipers bled easily and quickly with the Astrovan mc and JD7 calipers. The rear would not... read my 4 link/D60 build thread and you can see all the methods we tried. Anyway, I was told but never found or verified this but the AstroVan has a stepped mc which has a larger bore for the front and smaller for the rear. Made sense since we could not properly bleed the rear calipers. This could be part of Dan's squishy rear brakes also.

Yeller hooked me up with a 1.338" bore from a '85 Chev 1 ton and other than the pedal travel having to be increased the brakes are great- I mean great.

So I've been looking for an alum bodied mc with a plastic 100% sealing lid since my mc is on it's 3rd gasket and it still weeps fluid unless I use a radiator clamp on each end of the cap (looks redneck but 2 yrs now and bone dry).

Dan researched the OD and ID and after confirming measurements with a Astrovan reservoir I had... it fits. Already measured height to the hood and my '85 mc has less than 3/8" and this F350 mc with the Astrovan reservoir measures the same so I'm going to swap when I put my 6r80 in.

I'll be able to lower the brake pedal back to stock height too.

You're gonna love it DW!!

 

[toddz69]

I ran some quick math last night and it appears my current setup is very, very close to the ratios Ford used on my '01 SD. I'm going to run the numbers for the '08 F250 just for fun too. They must've really increased the size of the pistons if they went to a 1.5" dia. master cylinder.

Todd Z.

 

[nvrstuk]

Todd- glance underneath the newer SD frt axles. Stuff is humongous under there.!!

 

[toddz69]

Todd- glance underneath the newer SD frt axles. Stuff is humongous under there.!!

I know it!

Todd Z.

 

[Spaggyroe]

As for 1-ton vs Super Duty and year, not sure but my brakes are:

- Front - 89 Ford F350 Dana 60 stock calipers
- Rear - 76/77 Eldorado rear calipers

I must be bored... I collected all the MC and caliper piston specs for these 4 different scenarios to compare the caliper to master cylinder piston ratio:

Sorry, not to try and hijack this thread, but there's some great info going on here. I thought it'd be nice to have some other data points for commonly used calipers, so your findings can be more easily applied to other's applications.


Application - Diameter - Radius - Radius Sq - Surface Area

Stock Bronco 76-77 - 2.88 - 1.44 - 2.07 - 6.51
T-Bird - 3.11 - 1.55 - 2.42 - 7.60
76/77 Eldorado - 2.48 - 1.24 - 1.54 - 4.83


So for example, running T-bird calipers front and Eldorado calipers rear (7.6+7.6+4.83+4.83) = 24.85 sq inches of surface area.

Again, sorry for the hijack.

 

[DanWheeler]

Sorry, not to try and hijack this thread, but there's some great info going on here. I thought it'd be nice to have some other data points for commonly used calipers, so your findings can be more easily applied to other's applications.

No worries at all that’s why I do these project posts to share info and ideas. I’ll see if I can incorporate those numbers and update my grid. Thx

 

[nvrstuk]

Dan, if you can update the "surface area" post, could you put in the common GM JD6 and JD7 #'s. They are the most commonly used calipers when building axles if you dont keep stock stuff (which for example on a SD is extreme overkill in weight).

Thanks

 

[Yeller]

That’s awesome to hear. I have been wanting to do a new pump, hydro boost and a larger bore MC, but couldn’t come up with a combination that fit under the hood, I’m at 3/16” of clearance now with no room to move anything, I spaced the hood up so it wasn’t rubbing on the lid of the MC. Thanks!!

 

[DanWheeler]

That’s awesome to hear. I have been wanting to do a new pump, hydro boost and a larger bore MC, but couldn’t come up with a combination that fit under the hood, I’m at 3/16” of clearance now with no room to move anything, I spaced the hood up so it wasn’t rubbing on the lid of the MC. Thanks!!

FYI - I have 3" body lift but I'm guessing you do too if you have h-boost. This setup should be no larger than Astro hboost/MC combo.

 

[Yeller]

No hydroboost yet, just a 9” vacuum booster, it’s adequate but not awesome, however it is awesome compared to when I was running the stock sized 8” booster. I really need to get a better pump, my current Cadillac pump makes plenty of pressure but volume is barely enough to steer at lower rpm. I’m looking at doing a major rehash next year and this will be a priority.

 

[DanWheeler]

I just realized body lift has nothing to do with MC clearance since it all moves together on the firewall. Had it in my head that the body lift was somehow helping here. Derp. %)

 

[Yeller]

Hahaha I was just being polite and ignoring that

Knew you’d figure it out on your own

 

[nvrstuk]

That's what the ProFlow hoods for!!!

 

[Broncobowsher]

I just realized body lift has nothing to do with MC clearance since it all moves together on the firewall. Had it in my head that the body lift was somehow helping here. Derp. %)

But it does get you valve cover clearance.

 

[nvrstuk]

My HB/MC is moved 10+ " over from it's origninal location. Solves all kinds of issues

 

[DanWheeler]

Finishing up in the garage today, got the 2008 F350 hboost installed. It's pretty much a bolt in if you already have Astro hydroboost. All the fittings are the same and you can just re-use whatever plate or bracket you have.

As far as I can tell, everything is pretty much the same size. The hydroboost is the same casting but with a bigger flange to accept the bigger master cylinder.

The pushrod that comes with the 2008 F350 hydroboost is REALLY close to working out of the box. I almost used it as-is but it needs another 1/4" of length to allow the stock Bronco brake pedal to bottom out the hboost. I backed it off just a hair so the pedal hits the floor just before bottoming the hboost.

It would probably be fine to use the pedal rod as-is but I didn't want to risk it. If you're pedal gets that low, you probably better bail out or hold on.

I did run into a minor snag with dual large Astro reservoirs, they don't fit without removing the tabs that help you pull the top off the reservoir and they have to be oriented in a specific way to fit. But they fit.

At this point, the hboost part of the project is done and now I'm just obsessing over brake hose routing since I'm also re-doing that now and running all brake lines, vent lines and ARB lines down the panhard instead of a loose whip from frame to top of diff.

Dan

Hboost pedal rod bottomed out (note the clevis is not attached - I'm just using it to fully depress the hboost. Also note the black sharpie line)

Hboost pedal rod un-modified (not the black line does not go as far as it could)

I didn't get a picture of the modified pedal rod but now the black line goes just before where it was in the first picture above