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About PT81PlymouthPickup

  • Rank
    Advanced Member

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  • Gender
  • Location
    Yardley, PA 19067
  • Interests
    Machinery, Travel, Fishing
  • My Project Cars
    1939 Plymouth PT81 Pickup Truck

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  • Biography
    Yardley,PA resident working for Princeton University
  • Occupation
    Tool & Die Instructor


  • Location
    Yardley, Pennsylvania
  • Interests
    Retro Rodding

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  1. 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.
  2. That's promising to hear Ed. I agree the DCM looks pretty good. I'm hoping I might see at least one installed before considering purchasing. I reworked the original on my truck and it looks great, but it was pretty rusty and on the occasions when I get caught in the rain rusty water leaks out and leaves streaks on my paint. I think it's a matter of time before the rust surfaces through to the outside of the frame. The oem frames are so difficult to find a good one and they usually want too much money for them. IF? the reproduction is as good as it looks, I don't think the price is unreasonable.
  3. I see that a couple outfits are now selling reproduced windshield frames for the 39-47 Dodge and Plymouth trucks. I'm always skeptical about reproduction stuff, but from the photos they look pretty good? Seems like it would be difficult to make one that fit like the originals? Anyone have any experience with these? https://dcmclassics.com/glass-accessories/1083-gl-370-kit-windshield-frame-assembly-with-door-and-rear-glass.html?search_query=windshield&results=11 http://www.srpmstreetrods.com/srpm/1939-1947-dodge-truck-39-41-plymouth-truck-windshield-frame-painted-black-with-clear-glass-seals-40288bca4b105134014b5f820e6a1455-p.html
  4. 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?
  5. 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.
  6. 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.
  7. The geometry would be different on the front side depending on which master cylinder is used. I have a drawing of the one I made if anyone wants it?
  8. Made from scratch. I wanted to be able to reinstall the rubber boot to protect the back of the m.c. from dust, so I made one out of aluminum round stock as a prototype and then another out of stainless steel round stock. The alum. would have worked fine, but being too fussy for my own good I made another that will last forever. I am a machinist by trade and have access to lathes, mills, etc. which makes it a fairly easy project. Not sure why Mopar put the mounting holes on strange angles, but once you have them figured out, it's a basic lathe part. Steve 🙂
  9. Thanks Ed! I try to make things look good, but it doesn't always work out that way.
  10. Wow! I started this thread a while ago, got sidetracked and have just returned. Interesting discussion! Anyhow, to answer your question; Yes, I mounted the Delco #18M957 (95-2001 Jeep Cherokee) master cylinder and No it won't work because on my truck the pedal hits the floor before achieving full travel of the m.c. That's a No - No. So, I've installed a cast iron one from earlier 84-89 Jeeps (Bendix 11896, Cardone 13-2409, Wagner MC105876). It's a little tight but adapted easily and allows full pedal travel. It has a 15/16 bore which I'm hoping will work well with my system? I chose this one because the 90 - 95 Jeep Wranglers uses a m.c. with exactly the same casting only a 1"bore. I figured it would give me the option to go to the larger bore if I have too much pedal travel and I would not have to re-plumb the lines. After much research about custom brake systems I've decided to use a adjustable proportioning valve and 10lb residual valve in rear circuit and 2lb in front. It's still in process, so I can't report yet how it will work out, but I am hopeful. I've attached some photos showing my mounting adapter which allows the rubber dust boot to be reinstalled.
  11. Did you experience and increase in pedal travel after converting to the smaller bore toyota master cylinder?
  12. The length of the master cylinders in my photos are exactly 6 inches from mounting flange to front of master cylinder
  13. I'm in process of installing disc brakes on my 39 Plymouth PT81 1/2ton pickup. I did a bunch of research and concluded that Rusty Hope, Scarebird, and ECI all to be decent if installed correctly. Rusty hope uses a in - rotor hub which I liked better than the separate aluminum hubs the others use, but even having the skill, I did not want to modify my steering knuckles and steering arms. I believe also because Rustyhope's mounting plates are mounted between the steering knuckles and arms it might require changing tie rod length if there is not enough adjustment? ECI's rotors are customized (redrilled Firebird rotors for 4.5 b.c.) making it more of a pain if you ever need to replace them. Rustyhope offsets my wheels just about 1 inch out per side. ECI 1/2 inch per side and Scarebird 3/8 inch per side. Rustyhope and Scarebird claim no issue with using original wheels (16" on my truck). I ultimately chose Scarebird and a jeep master cylinder which several on p15-d24 have had good luck with the trucks. There's another kit offered by "The Ram Man" which uses all mopar parts which is cool, but on the trucks require some steering arm modifications. The Ram Man's videos are worth watching but he did not respond to some questions I sent him. I found the others decent about answering my questions. Anyhow, make sure kingpins and bushings are good first and keep posting your progress.
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