TRUCK MASTER CYLINDER UPGRADE ADVICE

[bkahler]

10 hours ago, PT81PlymouthPickup said:

Thanks Brad! Yes, the cast iron m.c. in my photos is exactly 8" long from mounting surface to the front. I'm fairly certain it will fit all 1939-47 Dodge and Plymouth pickups. Sounds like it won't work in yours? I was hoping the smaller Jeep aluminum master cylinders would work in mine, but the stroke was such that my pedal hit the floor before allowing full stroke of the m.c. I learned this could negate the purpose of a split system if you lose one half of the system from a hose or line rupture in an emergency situation.

 

I think at best depending on the shape of MC I might be able to fit about 6-7/8" in the opening but that would leave little to no room between the MC and the steering column.

 

As near as I can tell the Wrangler MC has a stroke that is about 1/8" longer than my original MC.  Until I get a chance to test drive mine I won't know if I made the right choice.  Worst case I'll just switch back to the original MC and call it good.

 

I've had the front brakes fail before on a split system and the pedal still went to the floor and there was no real stopping power available at that point.  I understand the concept of why split is supposed to be better but my one experience with it in real life didn't meet expectations.

 

 

[Merle Coggins]

What is the piston diameter of your Jeep M/C compared to the original unit? If the piston is smaller you will need more stroke length to move the same amount of fluid.

[bkahler]

20 minutes ago, Merle Coggins said:

What is the piston diameter of your Jeep M/C compared to the original unit? If the piston is smaller you will need more stroke length to move the same amount of fluid.

 

The Wrangler is 1".

[PT81PlymouthPickup]

42 minutes ago, bkahler said:

 

I think at best depending on the shape of MC I might be able to fit about 6-7/8" in the opening but that would leave little to no room between the MC and the steering column.

 

As near as I can tell the Wrangler MC has a stroke that is about 1/8" longer than my original MC.  Until I get a chance to test drive mine I won't know if I made the right choice.  Worst case I'll just switch back to the original MC and call it good.

 

I've had the front brakes fail before on a split system and the pedal still went to the floor and there was no real stopping power available at that point.  I understand the concept of why split is supposed to be better but my one experience with it in real life didn't meet expectations.

 

 

Yes, I believe split systems were government mandated sometime in the late 60s early 70s for safety. Did you have a warning light? Without a warning light, you could potentially lose your rear circuit and might not even notice it. Then if later the front circuit were to fail, no brakes at all. ? That's why the pressure differential warning lights were added. Perhaps something like that happened? I've read many times that if you do not have full m.c. travel before pedal hits the floor you might not get any braking if half of your system fails.  My 39 brakes failed me when a deer jumped into my path. I slammed the pedal and no brakes. I almost rolled the old girl and narrowly avoided a collision with another car. ? That's what prompted me to upgrade to front disc and a split system. I've also read that combination valves were designed to be used on specific vehicles and if weight, center of gravity, wheelbase, drum / disc and caliper / wheel cylinder sizes, etc. are not the same as the vehicle they were designed for it can make a vehicle hazardous in an emergency braking situation. Might work perfectly until a panic stop. For a customized system most of the knowledgeable street rod builders recommend adjustable proportioning valve to adjust the front / rear bias for panic stops.  They test them and adjust to prevent rear wheel lockup which is extremely dangerous in a panic stop.

[PT81PlymouthPickup]

1 hour ago, Merle Coggins said:

What is the piston diameter of your Jeep M/C compared to the original unit? If the piston is smaller you will need more stroke length to move the same amount of fluid.

My 39 originally had a single circuit 1.250 dia. bore m.c. The Jeep Cherokee m.c. I just installed has a 15/16 dia. bore and the Jeep Wrangler which uses the same casting has a 1" bore. If I end up with too much pedal travel? I can easily switch to the 1" bore without changing any plumbing geometry and hope it still produces enough pressure to stop well?

[Tooljunkie]

Remember, original master split a single  piston Between 4 wheels. 
now two pistons are in play here. 
so even 15/16” should be enough. 
that’s what i’m banking on in my case. 

[bkahler]

Finished fabricating the adapter plate today.  I opted to use a countersunk bolt on the bottom so I wouldn't have to grind on the master cylinder.  The plate is made from 1/2" 6061 aluminum plate. 

 

It takes a little finagling but I was able to bolt the plate in place first and then I was able to wiggle the MC into place as well.  I still need to weld a section onto the end of the push rod to make up about 5/16" difference in the first MC that I tried.  

 

I measured my original MC and it had 1-1/2" of piston stroke.  This Wrangler MC seems to have about 1-5/8" stroke.  I think that's close enough for government work

 

Brad

 

[ggdad1951]

14 hours ago, bkahler said:

Finished fabricating the adapter plate today.  I opted to use a countersunk bolt on the bottom so I wouldn't have to grind on the master cylinder.  The plate is made from 1/2" 6061 aluminum plate. 

 

It takes a little finagling but I was able to bolt the plate in place first and then I was able to wiggle the MC into place as well.  I still need to weld a section onto the end of the push rod to make up about 5/16" difference in the first MC that I tried.  

 

I measured my original MC and it had 1-1/2" of piston stroke.  This Wrangler MC seems to have about 1-5/8" stroke.  I think that's close enough for government work

 

Brad

 

 

 

good job!  Looks like it will work well!

[PT81PlymouthPickup]

I thought I'd update my disc brake and split master cylinder install progress just in case anyone is interested? Finished bending brake lines needed for the conversion today. I'm using a copper / nickel alloy called NiCopp. Never used it before. I've read it meets oem safety standards and has been used for many years on European cars. I wish I knew about this before. Wow! Is this stuff way better to work with than steel or stainless. Bends and flares like a dream. That said, fabricating brake lines is still a royal pain. Laying on the cold concrete floor wasn't much fun either.  Anyhow, I wouldn't refuse any constructive criticism, if any experts out there see something I've missed?  Next thing to do is get the brake hoses and mount to the calipers.

[Tooljunkie]

Looks great! I wouldnt change a thing. 
have to mention, when i removed the rear brake line from my ,truck, i clipped both ends and yanked it out. Then i went to bend it in 1/2 a couple times to throw in scrap bin. 
grab ends and bend. Can you believe it made a perfect radius without kinking? 70 years old and that line is better than anything i can buy today. 

[ggdad1951]

that's some purdy plumbin'...be a shame to get it dirty driving it!

 

[1936Forepoint]

Hi PT81PlymouthPickup. I have followed the discussion on the Master Cylinder change options and your approach seems the most reasonable.  It's a bit hard to follow sometimes which cylinders work and which ones don't.  I am going with a disc/disc setup on my 1936 pickup and I have some questions that would be best on the phone.  Would you be willing to give me a call at 916-893-5419.  Thanks.  Bob Akin.  California.

[48Dodger]

On ‎2‎/‎23‎/‎2020 at 4:21 PM, PT81PlymouthPickup said:

Anyhow, I wouldn't refuse any constructive criticism, if any experts out there see something I've missed? 

 

The adjustable port valve is in a tough spot. I realize you could dial it in lil by lil....but having it up top would make it easier to make those adjustments.

In circle track racing, the port valve is next to my shifter for adjustments on the fly. The rear brakes need to come in after the front brakes. 

It may not seem off until you hit it hard and lock up the back before the fronts have a chance to do their job.

The plumbing is first rate, but I would like better access to the knob.      imo

 

48D

[tanda62]

Your work looks great!  I used NiCopp as well and agree on how much easier it is than stainless.  I did take some rubber fuel hose, split it and wrapped it around the brake lines where I thought it might be exposed to rocks and such from the road as an added protection.  Might be overkill but if it keeps a line from being damaged worth it.

[Jeff Balazs]

On 4/28/2020 at 1:18 AM, 48Dodger said:

 

The adjustable port valve is in a tough spot. I realize you could dial it in lil by lil....but having it up top would make it easier to make those adjustments.

In circle track racing, the port valve is next to my shifter for adjustments on the fly. The rear brakes need to come in after the front brakes. 

It may not seem off until you hit it hard and lock up the back before the fronts have a chance to do their job.

The plumbing is first rate, but I would like better access to the knob.      imo

 

48D

I would like to comment on this installation. First off it looks like you did a first class job on it. Bravo!

As far as adjustments go I think what you did is just fine. In reality you may make a few adjustments early on to get the correct balance in your braking system. But once you have got it where you want it you won't actually need to touch it. I have had my truck in daily use for over 5 years now and have not had to make any further adjustments. Of course I don't race it....but it has been used more than most trucks here.

Hth, Jeff

[bkahler]

A while back Tinlizzy (Lee) asked me to fabricate an MC bracket for his truck.  Attached are a couple of pictures of the bracket installation on his truck.  One question that came up was what to do about the brake switch.  For myself I am replacing the union that mounds on the frame behind the MC with a T and will mount the brake switch there.  What have others done?

 

Brad

 

 

[John-T-53]

On 2/23/2020 at 4:21 PM, PT81PlymouthPickup said:

I thought I'd update my disc brake and split master cylinder install progress just in case anyone is interested? Finished bending brake lines needed for the conversion today. I'm using a copper / nickel alloy called NiCopp. Never used it before. I've read it meets oem safety standards and has been used for many years on European cars. I wish I knew about this before. Wow! Is this stuff way better to work with than steel or stainless. Bends and flares like a dream. That said, fabricating brake lines is still a royal pain. Laying on the cold concrete floor wasn't much fun either.  Anyhow, I wouldn't refuse any constructive criticism, if any experts out there see something I've missed?  Next thing to do is get the brake hoses and mount to the calipers.

 

 

 

 

Looks nice. I haven't heard much about the nickel-copper lines myself, but sounds like they were a breeze to work with. I used stainless and it was a b*****!

 

What are the Wilwood inline connectors for?  

 

 

[PT81PlymouthPickup]

On 5/16/2020 at 2:02 PM, John-T-53 said:

 

Looks nice. I haven't heard much about the nickel-copper lines myself, but sounds like they were a breeze to work with. I used stainless and it was a b*****!

 

What are the Wilwood inline connectors for?  

 

 

They are residual check valves. The original master cylinders had a internal valve which would hold about 10 psi on the system. Very important on vehicles with master cylinder mounted below floor. They keep the fluid from draining back. New master cylinders don't have internal residual valves. So you need to add them when converting to a newer split system mc. With disc brakes on front 10psi is too much. Typically 2psi for discs. Blue one is 2psi and red one is 10psi.

[ggdad1951]

On 5/16/2020 at 1:02 PM, John-T-53 said:

 

Looks nice. I haven't heard much about the nickel-copper lines myself, but sounds like they were a breeze to work with. I used stainless and it was a b*****!

 

What are the Wilwood inline connectors for?  

 

love the cupro-nickle line material, bends like copper but strong like bull! And will NEVER rust.

[John-T-53]

17 hours ago, ggdad1951 said:

 

love the cupro-nickle line material, bends like copper but strong like bull! And will NEVER rust.

 

On the master cyl to chassis line, I bump-formed the loop, and happy with the way it turned out, but I wonder if it'll ever be prone to cracking? 

 

@PT81PlymouthPickup did you get that tube material at classic tube?

[PT81PlymouthPickup]

@PT81PlymouthPickup did you get that tube material at classic tube? 

 

No, I bought it from  rockauto.com  Do a search for hydraulic line and you should find it there. AGS CNC3 {#CNC3100, CNC325, CNC350} NiCopp® Nickel/Copper Brake Line Tubing Coil, 3/16". A 25 foot roll cost me around $36. including tax and shipping.  You might find it cheaper locally?