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

[gunnibronco]

In a post above, I said I put my HB on when I was on 33s, but now I'm on 37s, so the confusion is understandable. LOL.

There seems to be a few options for making the push rods fit. Some are cutting/threading them to lengthen, some are shortening them. I think the SD HB sticks out so far the 1/2" adapter plate makes them match the Dodge MC perfect. You can also buy new push rods and cut to length.

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[DanWheeler]

ah ok, well glad to know these companies are thinking about the rod length.

If you go with SD HB, you might also have to lengthen the pedal pushrod a bit too. I have some pics of that at the top of this thread. I think I only need another 1/4" just to make absolutely sure my brake pedal was able to bottom out the H-boost. I don't think that even happens in reality so you could probably just use the pedal pushrod as-is. 50 years later and it's the exact same size hole on the rod!

 

[toddz69]

I think the SD HB sticks out so far the 1/2" adapter plate makes them match the Dodge MC perfect. You can also buy new push rods and cut to length.

That is correct. My adapter plate is 1/2" thick and works perfect with my SD booster and Dodge master cylinder (with booster rotated 90 deg.).

Todd Z.

 

[DEEPWOODS]

I tried several different MC and I could not get my rear calipers to even bleed till I did Dans SD -MC now my brakes works great .I think it depends on what size calipers you are using the small bore master cylinders just don’t move enough fluid for large calipers .

 

[DirtDonk]

Which I always thought was interesting because for my situation anyway, my 79 F350 has a 1 inch bore master cylinder and those big front discs and huge rear drums.
Although I don’t remember the size of the wheel cylinders in the rear, which would really be what dictates the amount of fluid needed to work.
But I always thought that it was funny to see a 1 inch bore coupled to those massive dual piston calipers.
However my pedal was high and firm and brakes worked amazingly well.

I wonder what the pedal ratio is and if that has anything to do with it.

 

[gunnibronco]

I tried several different MC and I could not get my rear calipers to even bleed till I did Dans SD -MC now my brakes works great .I think it depends on what size calipers you are using the small bore master cylinders just don’t move enough fluid for large calipers .

Thanks, that is good to hear. I'm moving forward with the 08 SD master. What front/rear calipers are you running? I debated 1.25" vs 1.375" vs 1.5" MC bore. The only negative from using the 1.5" MC should be a touchy brake pedal, if I understand right. I loved my set up with 1" MC, F150 front calipers, F150 rear drums- the pedal was super firm. I lived with the softer/longer pedal when I went to T-bird calipers, but preferred the tighter pedal with the F150 calipers.

Which I always thought was interesting because for my situation anyway, my 79 F350 has a 1 inch bore master cylinder and those big front discs and huge rear drums.
Although I don’t remember the size of the wheel cylinders in the rear, which would really be what dictates the amount of fluid needed to work.
But I always thought that it was funny to see a 1 inch bore coupled to those massive dual piston calipers.
However my pedal was high and firm and brakes worked amazingly well.

I wonder what the pedal ratio is and if that has anything to do with it.

There are so many variables with this, and I can't say I have truly wrapped my head around all of it. I think the pedal ratio has more to do with how hard you have to push to get adequate pressure, when everything else is kept the same. I *think/hope* hydroboost makes that a non-issue in my Frankestein set up.

EDIT- I looked and your calipers are dual piston at 2.18" diameter each, and the wheel cylinders are 1" (79 F350), 85 F350 specs a 1.125" MC, with the same calipers and wheel cylinder sizes.

 

[DanWheeler]

Thanks, that is good to hear. I'm moving forward with the 08 SD master. What front/rear calipers are you running? I debated 1.25" vs 1.375" vs 1.5" MC bore. The only negative from using the 1.5" MC should be a touchy brake pedal, if I understand right. I loved my set up with 1" MC, F150 front calipers, F150 rear drums- the pedal was super firm. I lived with the softer/longer pedal when I went to T-bird calipers, but preferred the tighter pedal with the F150 calipers.


There are so many variables with this, and I can't say I have truly wrapped my head around all of it. I think the pedal ratio has more to do with how hard you have to push to get adequate pressure, when everything else is kept the same. I *think/hope* hydroboost makes that a non-issue in my Frankestein set up.

EDIT- I looked and your calipers are dual piston at 2.18" diameter each, and the wheel cylinders are 1" (79 F350), 85 F350 specs a 1.125" MC, with the same calipers and wheel cylinder sizes.

@gunnibronco are you switching out your HB to 2008 also? Do you have a body lift? I wonder if that reservoir on the 08 MC will fit. I think you'll be fine on brake feel/touchiness. I think you said we have the same ~2" dual-piston calipers up front and I have Eldorado calipers in the rear which are smaller than your JB7 and my brakes aren't too touchy. They are definitely more touchy than a typical old truck without hydroboost but not as touchy as a lot of modern cars. Somewhere in the middle.

 

[gunnibronco]

@gunnibronco are you switching out your HB to 2008 also? Do you have a body lift? I wonder if that reservoir on the 08 MC will fit. I think you'll be fine on brake feel/touchiness. I think you said we have the same ~2" dual-piston calipers up front and I have Eldorado calipers in the rear which are smaller than your JB7 and my brakes aren't too touchy. They are definitely more touchy than a typical old truck without hydroboost but not as touchy as a lot of modern cars. Somewhere in the middle.

Thanks for the feed back about the "touchy" pedal. I see that as the only possible downside of the giant 08 MC, hopefully. I'm increasing my total brake caliper surface area by about 174% 16.692 to 28.87 sq in, almost all the increase is the rear end. So a 150% increase in the MC bore doesn't seem out of line. My current MC/surface area ratio is 16.56:1 and my ratio with my new set up should be 19.25:1, the stock 08 F350 ratio is 19.05:1, so everything kind of makes sense.

Right now I'm going to try to make the Mustang HB work. I know you don't like the idea of the spacer between the HB and MC, but that is where I'm heading. I'm pretty sure the SD HB won't fit in the stock configuration, the accumulator will hit my EFI upper. I don't know if it will fit turned 180*, I'm afraid the accumulator will hit my steering column. Even if it does fit, I'll have to get into figuring new hoses, pedal push rod.

So much of my truck is no longer "DOT", I don't know if the HB/MC matters. I'm running beadlocks and home fab'd suspension, not to mention my axles will be fab'd hybrid axles. I'm also having problems finding DOT brake hoses to match everything.

I don't have a body lift, and I can't imagine the 08 reservoir will fit. I took some measurements and from the center line of my MC to my hood I only had 6" max. The 08 MC with reservoir measured 7.5". I'm going to use your Astro reservoirs.

 

[DanWheeler]

Thanks for the feed back about the "touchy" pedal. I see that as the only possible downside of the giant 08 MC, hopefully. I'm increasing my total brake caliper surface area by about 174% 16.692 to 28.87 sq in, almost all the increase is the rear end. So a 150% increase in the MC bore doesn't seem out of line. My current MC/surface area ratio is 16.56:1 and my ratio with my new set up should be 19.25:1, the stock 08 F350 ratio is 19.05:1, so everything kind of makes sense.

Right now I'm going to try to make the Mustang HB work. I know you don't like the idea of the spacer between the HB and MC, but that is where I'm heading. I'm pretty sure the SD HB won't fit in the stock configuration, the accumulator will hit my EFI upper. I don't know if it will fit turned 180*, I'm afraid the accumulator will hit my steering column. Even if it does fit, I'll have to get into figuring new hoses, pedal push rod.

So much of my truck is no longer "DOT", I don't know if the HB/MC matters. I'm running beadlocks and home fab'd suspension, not to mention my axles will be fab'd hybrid axles. I'm also having problems finding DOT brake hoses to match everything.

I don't have a body lift, and I can't imagine the 08 reservoir will fit. I took some measurements and from the center line of my MC to my hood I only had 6" max. The 08 MC with reservoir measured 7.5". I'm going to use your Astro reservoirs.

cool cool, I think those spacers are fine as long as the pushrod between the HB and MC is lengthened the same amount. I thought people were adding a spacer without lengthening the rod. I'd do a spacer before I did an angle bracket. Do you have to make your own plate or do the ones on the market already have a big enough hole for the MC? Do the two mounting bolts align to the 08 SD MC?

 

[gunnibronco]

I'll probably build my own spacer. I've only found 2 on ebay. One is only .25" deep (I'll need .5"), the other looks ok but states it doesn't work with Mustang H-boost, it's also $120. I can make one for a lot less. I've contacted Catfan on here and he can build a pushrod to order, or he suggested adding a "bullet" to make up the difference in length if it will work that way. I'll see how everything fits together and then move forward on the spacer and pushrod. I'm expecting the MC and reservoirs mid week.

 

[gunnibronco]

I received my 08 SD MC and Astro reservoirs and I don't think they will work with my Mustang HB.

I did some test fitting with the HB in the stock position last night. The accumulator extends past the HB/MC flange and would require a 1.25" spacer between the HB and MC due to interference between the accumulator and reservoir. I don't think I feel very good about a spacer that long.

This weekend I'll try clocking the HB to see if it will possibly work. It appears with a .5" spacer the Mustang HB push rod length would actually be very close to perfect, if not a little long and need shortened. I think the best position for the HB/MC that would work very well with a .5" spacer will put the hoses in the same space as the steering column. I'll be surprised if I can find a position that will work.

I've been giving a SD HB a lot of thought. From your pics, I know the stock position will have interference between the accumulator and EFI upper intake. I see 2 other options, flipping the HB 180* will be great if the accumulator and hoses clear everything in that position. The other option is to turn the HB 90* as many are doing. I'm pretty sure this will work with a clocking ring to mount the MC to the HB. This will then require a bullet or longer HB push rod, the length of the clocking ring thickness. I'd expect it could be made of .25" plate or use one like Catfan sells on ebay. I'm going to see what the center bore of his plate is, if it will accept the huge 1.75" SD MC.

 

[toddz69]

I've been giving a SD HB a lot of thought. From your pics, I know the stock position will have interference between the accumulator and EFI upper intake. I see 2 other options, flipping the HB 180* will be great if the accumulator and hoses clear everything in that position. The other options is to turn the HB 90* as many are doing. I'm pretty sure this will work with a clocking a clocking ring to mount the MC to the HB. This will then require a bullet or longer HB push rod, the length of the clocking ring. I'd expect it could be made of .25" plate or use one like Catfan sells on ebay. I'm going to see what the center bore of his plate is, if it will accept the huge 1.75" SD MC.

View attachment 878665

I'd really encourage you to give the SD booster with a 90 deg. flip a strong consideration. The 180 works too (I ran mine that way for years) but hose/fitting access is a lot easier with the 90 deg. flip.

Todd Z.

 

[gunnibronco]

I'd really encourage you to give the SD booster with a 90 deg. flip a strong consideration. The 180 works too (I ran mine that way for years) but hose/fitting access is a lot easier with the 90 deg. flip.

Todd Z.

Thanks for the input.

 

[DEEPWOODS]

gunnibronco the front calipers are chevy blazer and the rear are bc broncos disc conversion I think they are also Chevy.How I found out why I had spongy brakes is I blocked off the rear fluid line and the pedal was nice and firm then I only blocked off the passenger rear caliper line and still nice and firm as soon as I added back the Passenger caliper it went back to spongy brakes . I think The rear drum caliper pistons are smaller so the 1 1/4 MC seam to work .I just know that Dans SD - MC Fixed my problem

 

[gunnibronco]

I've gathered up what I need to install the SD booster (salvage yard) and MC (new). I'm planning to build a clocking ring to turn the HB 90* to clear the EFI upper. My new axles are taking longer than expected (I should have expected that) so I haven't started any of the brake install yet.

Do you know which port feeds the front brakes and which feeds the rears? I don't have a SD handy to look at to figure out which MC port feeds which brakes.

I assumed the front brakes are fed from the port closest to the firewall. I thought almost all MCs were configured that way. Recently I saw a post of some old info on Hydratech's web site that showed quite a few MCs plumbed the other way (rears closest to the firewall). It crossed my mind that may be why you can't get your fronts to lock up. I had that issue when I first installed my Mustang HB/MC, I got bad info and had it plumbed backwards. Even with a prop valve turned all the way down, the rears would lock and the fronts wouldn't. From the Hydratech info all the MCs have a 65/35 proportioning built in to feed the front more fluid, if that is mixed up you'll never get good front brakes.

Thanks

 

[gunnibronco]

Here is my progress.

I built a clocking ring and spacer. It had to be .5" to clear the MC reservoir from the booster can on the HB. I used my angled mounting plate from my Mustang HB since my firewall was already drilled for this. It was probably unnecessary but added a little extra space between the EFI upper and the HB/MC. Still need to adjust the PS hoses, lengthen the pedal push rod, and make a .5" bullet spacer for the HB/MC interface to match the clocking ring.