disc/drum conversion

S

skylarkman2

Member
I apologize if this has been covered, but my search found little info.
I am building a 46 for tudor deluxe.
I am using speedway's front disc conversion, and stock drum rear brakes.
This kit uses the 73-77 ford p.u. rotors and 71-76 chevy calipers.
This allows the use of 15" ford p.u. wheels.
I also decided to use a dual master cylinder and 7" dual power booster unit.
Chrome units are available about the same or less than stock units.
I fabricated a bracket and linkage to mount the booster and m.c.
The complete system is connected with a disc/drum proportioning valve and residual pressure valves.
I pressure filled the lines from the cylinders back to the prop valve.
Bench bled the master through the prop valve.
That should minimize any air to be bled off.
I have not been able to get the brakes to pump up. Absolutely no pressure.
I have about concluded that the m.c. is bad.
Surely I am not the first to try this setup.
dave-TX
 
Pressure bleeding the system backwards, as I understand you did, is not correct or good, and could result in prop valve, residual and master cylinder damage. Pressure should originate from the master and out to the entire system.
More details and/or a picture of the master location, mounting and linkage would be of help.
 
Need a proportioning valve and a 10 LB and a 2 LB residue valves and make sure the MC rod to pedal is adjusted-- call speedway tech they can answer it for you--- easy fix
 
Thanks guys.
The booster and MC are mounted in the area below the floor where the original mc would be.
I will try to get a picture of it.
The prop valve is a common setup for disc/drum systems.
There is a 2 lb. residual forward and 10 lb. to the rear.
I bench bled the mc first and then installed.
I did not reverse pressure bleed, just pre-filled the cylinders, calipers and lines from the wheels back to the residual valves. No real pressure, just filling back to where I opened the lines at the residual valves.
After connecting everything up, I could not get any pressure with the mc.
I did another bleed connecting the tubes from the output ports on the prop valve back into the mc. After connecting all again, still no pressure.
I am thinking that I have a bad mc.
I have put off calling speedway tech, but that may be the best answer.
 
Any reason you didn't just bleed the system in the normal manner? Not sure I understand the reasoning behind all this pre-filling. I've installed a lot of brake systems and never resorted to any of this. I would start over with bench bleeding the master cylinder and then bleed the system in the normal manner. Keep an outlook for a connection that is leaking air into the system.
 
Installed virtually the same system and had the same lack of brake and bleeding problems. Finally installed a set of Russell Speed Bleeders and the problem was cured.
Not saying these will cure your problem but for the price it may be worth a try.
 

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A couple years ago I took apart my front brakes for some new parts and when I reconnected them I could not get the MC to pressurise no matter what I tried. I even have a air operated vacuum brake bleeder and they still wouldn't work. Finally picked up a new MC and it worked like a charm. I never did figure out why the previously working MC wouldn't work.

Maybe try finding a vacuum bleeder that you could borrow or rent. It sure make bleeding a whole lot easier.

https://www.amazon.com/Mityvac-6830-Brake-Bleeder/dp/B000JFN9WC/?tag=atomicindus08-20
 
I usually try to make my experiences (good and bad) available to others.
I will continue to report on the progress of this situation.
The speed bleeders are a great idea, and I would recommend them.
I have long used a vacuum pump. It makes it easier for a one man operation.
That is why this has been so frustrating. All normal procedures have not worked.
I am going to try to isolate the mc and see if I can verify that is or is not producing pressure.
Stay tuned.
 
Did you put the "slug" in the master cylinder piston that gives the push-rod on the booster something to contact?
 
Hi Skylarkman2. Have a BUNCH of 46-48 Ford stuff that needs to leave my garage this weekend. Will make you a great deal on a package deal. Live in Burleson. Call me at 817-308-2709. Unable to go to Pate.
 
If you still suspect the master cylinder, install plugs (or short crimped off lines) in the outlets and see what you get for pedal.
 
Randy in ca said:
If you still suspect the master cylinder, install plugs (or short crimped off lines) in the outlets and see what you get for pedal.
Click to expand...

Charlie Stephens said:
Dave,

The reason you found little info in the archives is that the charter of this site is restored (or slightly modified) vehicles. Try your question on HAMB, https://www.jalopyjournal.com/forum/. Good luck with your project.

Charlie Stephens
Click to expand...
Considering that this thread originated well over a month ago, I wonder if the original poster has been waiting with anticipation for this information.
 
Maybe you should ask the new member CorvetteSally who brought it back up. At least there was a point to our replies - what's your's?? Our apologies for not noticing!! :rolleyes::rolleyes:
 
skylarkman2 said:
I usually try to make my experiences (good and bad) available to others. I will continue to report on the progress of this situation.............this has been so frustrating. All normal procedures have not worked. I am going to try to isolate the mc and see if I can verify that is or is not producing pressure.
Stay tuned.
Click to expand...

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Any updates since your last post??
-
 
CorvetteSally said:
Hi Skylarkman2. Have a BUNCH of 46-48 Ford stuff that needs to leave my garage this weekend. Will make you a great deal on a package deal. Live in Burleson. Call me at 817-308-2709. Unable to go to Pate.
Click to expand...

Catching up myself.
I have started cleaning up a lot of my extra stuff - not just ford.
I sold a bunch on ebay and have some listings now and more to follow.
I probably won't make it to Pate either.
 
Thanks Charlie.
It is hard when you just like old cars all the way from purist to total customs.
You are right though, I should take the question to the HAMB.
 
Sorry that I haven't posted any updates for a while. Long story.
The master cylinder was bad. It came from Skip White Performance.
A series of mis-communications, but I did receive the replacement just today.
The new one is obviously better quality.
I will try to give an update in a few days.
I will also try to report all this over on the HAMB.
 
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