In my quest to relocate and update the master cylinder in my '37 I am encountering small hurdles along the way. My newest is making a longer push rod / plunger for the master cylinder. I need a rod about 12-18 long. Does the end going into the master cylinder have to be a certain shape or will a rounded end work fine? One master cylinder I am looking at using is for a car manual drum/drum and has a shallow hole for the rod to go in to. Is there a way to make sure the rod doesn't fall out or do I just use the pressure from the pedal to hold it in place. I'd like to see examples of what others have done. Thanks
a rounded end will likely be best, considering the shape of the plunger is bowl shaped. if your worried about the rod falling out use a light spring to keep tension.
Last time I needed one I went to U-pull-it and walked the GM row....nothin! They are all non-adjustable. Stepped over to the ford row and had m choice of several lengths with adjusters. I made one for my old 53 F-100 with under-floor mounted master cylinder. Needed to be about 14-16 inches if I remember right..I used the ford adjustable end from a bronko II and the other end from the stock F-100 pedal. In the middle I used thick walled tubing and welded the ends into the tubing for a very stout linkage rod. Worked for me. Oh yeah, just rounding the end of a linkage rod will be ok too and if it's the correct length, I see no need for a spring. Too heavy a spring would keep pressure on the master cylinder, causing the brakes to drag all the time...how 'bout a heavy wire "J" hook hanging from the floor to catch the linkage rod in case it fell out?
If the master has a shallow hole in the center of it, it is from a power brake set up. The one for manual brakes has a deep hole in it to retain the rod. Get one for manual and you will be all set.
BigAl, I'm pretty sure I've read on the HAMB the power units have the deeper receptacle. The unit I have is for manual brakes and it has a shallow receptacle.
This is the one I bought, it's for a '69-72 GM mid sized car with power or manual and also many models of Jeeps with manual brakes. It has a shallow hole. A Model Man, can you find a part number for the rod and boot? I've searched and called around and no one has them. Thanks, Bob
My experience is the manual one was deeper. EDIT: FWIW I think some of them the metal slug at the end of the MC would come out depending on if your application was power or manual brakes. I had a problem with the rod falling out. For some reason if you accidentally hit the back of the pedal towards you coming off the gas to the brake it could knock it out. I'm not sure if the pedal didn't have a return spring on it or what exactly. I guess I'm not much help, I ended up throwing it out and going with power brakes
I went through this a couple years ago - I went to a couple parts stores - each one selling me a DEEP hole & calling it a POWER M/C when I needed shallow for my booster. Now I'm NOT arguing with the guys calling the shallow ones power - that's how I was taught - it WAS funny that every parts store in town was calling (& stocking them) the opposite way around. Don't let them confuse you!!!! BTW an 18" long rod is VERY VERY LONG. Keep in mind that to do this right (safe) you're gonna wanna make it substantially larger in diameter. Mine is the same way - I think (IIRC) I used 3/4" tubing and welded threaded inserts in it to get the ends teh right size. Think twice on this - I've even seen aftermarket ones use the standard 3/8" dia rod that long - - not wise IMHO.
Just an update. I found a '72 Skylard on Craigslist not far from me. I bought it for the core and the pushrod. This car had the same master cylinder with the shallow hole and the rod had a metal collar to help hold it in place.
What I did on my 52 was make my own rod and I ran three short round stock cut rings tacked to the frame to hold it in place. never failed to stop.
the aftermarket rods i've seen are about 8". either weld the stock end to some bar stock or machine the bar stock to accept the stock ends, also use thicker stock because of the length.
I have the system assembled, I need to clean it up. I used the old master cylinder I bought today and piece of threaded rod just to make measurements. I bend and mounted a plate to mount the master cylinder one. I was able to sandwich the cup that the rod goes through between the plate and the master cylinder, there is a recess in the boss of the master cylinder so the mounting ears of the master cylinder are flat against the plate. This will prevent the rod from falling out. I have a push rod from a '40 Buick, which is a lot longer than the one for the one used on a '37 at 11", unfortunately, it's about an inch too short. It's made of 7/16" rod so I feel it'll be safe to use a piece of 7/16" rod to make the rod I need.
was the floor or exhaust going to be in the way if you put it on the stock bracket in front of the one you made?. that's one long push rod...
Good point. Does it need to be so far back? IMHO if you use that long pushrod, I would beef it up to at least 9/16 heavy tube, drilled and tapped for adjustment. Better to be over cautious when it comes to brakes...
The reasons I have it mounted where I have it is access to the mounting bolts and rod adjustments and I also want to install a rubber boot or some other form of protection over the shaft. I also didn't want to block access to the rear transmission brace bolts. I am trying to find out where the exhaust runs. The car didn't have an exhaust system when I got it. I'm not at my shop right now and only have the couple of pictures I posted for reference. The master cylinder has to stay in alignment with the pedal so it has to stay where it is, it could go forward if need be. I'm not too concerned about the length of the rod. I have the rod from a '40 Buick and it measure 11", I need 12". The '40 master is located forward of the pedals and pivot above the pedal pivot unlike the '37-39 which is on the bottom and goes back.
Well, I guess I make a slight miscalculation, the exhaust runs in the general area where I have the master cylinder mounted. I'll have to move it over about 2". I looked into using the stock bracket but I couldn't get a straight shoot to the pedal. There wasn't metal to mount to where I had to mount it.
Just an update. Thanks to 1oldtimer's observation I realized my original mounting bracket was in the way of the exhaust mounting. I built a new bracket using heavier metal and moved the master cylinder over about 2". I made the on piece push rod out of a 1/2" rod. I have an original rod from a '40 which was made from 3/8" stock. The rod I made is only a few inches longer and I am confident that the 1/2" will work find.
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