Projects Master cylinder pushrod

Question about a master cylinder setup.

I'm doing a 32 build and have the So Cal Speed Shop K member with the master cylinder and pedal mounts. I bought a standard dual feed master cylinder without the pushrod so I could fab up the length that I need. While building it, I realized there's nothing to hold the pushrod against the cylinder. Looking at other MC kits, it looks like there's some sort of clip or something holding the pushrod in place. I'm not expecting the boot to hold it.

I mounted the MC, made a pushrod from a 9"×5/8" grade 8 bolt then had to make a plate to hold it in place. I'll probably have to make some other plate to hold the boot on too.

It seems like it would have been easier to get the whole setup as one, but my question is has anyone had to rig up something like this too? Thoughts on this setup?

 

Never used anything that offset, but I've used a long extender (9" long) between the stock rod ends and a deep bore master to hold the rod from moving.....and of course the pedal return spring.

 

Yep, wrong master cylinder. The 'manual' type (ie not for use with a booster - without modification) have a bore of an inch or so which prevents the rod from falling out. No need for retaining plates or anything. Pretty sure SoCal sell a rod for their application too, and a master.

I'm a bit surprised at the apparent offset of the pedal to the master on the SoCal frame, which is making me think you have set something up wrongly. Either the heim needs to be on the opposite side of the pedal or maybe you should be using a clevis? The pic of the master without he plate seems to show it mounted somewhat outboard of center, but it might be the camera angle?

Chris

 

Some power master cylinders, like the Fords I use, have deep push rod bores, while other makes and model manual masters have the deeper bores, so if you are not going to use a factory style push rod retainer, you need to use a master with a deep primary piston bore to contain the push rod. Your external guide plate without a bushing or bearing is not the answer.
I would not use your offset push rod. You need to move /realign the pedal tab/push rod/ and/or master cylinder for a straight path into the master.
And yes, you need a boot for the master.

 

Your making a huge mistake with that offset push rod.
Number one you will lose leverage or power to the M/C piston from side bind
Number two it will eventually bend
Number three see numbers one and two
This whole thing goes against the law of physics.

 

Thanks. I'm definitely thinking something isn't right. I can't be the first person to encounter this and haven't seen a setup like this.

The MC has about a 1"deep bore but there's nothing inside that would hold the pushrod in place. There is that retaining ring, which you can see in the picture, but that looks to hold the piston in. I tried to run a straight pushrod, which I can, but it's still at a slight angle from the pedal to the MC, but there's nothing to hold it.

It's a So Cal MC so I'll see what they have to say about it. But it didn't come with anything other than the MC, no boot, no retaining clips or parts.

I don't know how they weld up their K members but I assume they're jig mounted to set everything properly.

 

The pushrod should be 3/8ths and goes deep into the MC, it fits kinda loose in the bore but has to be in straight shot to pedal clevis or it'll bind up as you push it in. Your pushrod at 5/8ths is just too big to fit the hole. Looks to me like your pushrod is coming from the clutch pedal, move it to the inside pedal with a clevis and looks to me like it'll be good to go.

 

I don't know if you have ever seen one but there is a small star shaped clip, for want of a better description, which goes on the end of most brake pedal pushrods. The pushrod is inserted into the piston and pushed until it clips into place. This sort of locks the push rod inside the piston to prevent it from falling out. The only way I know of to get one out once installed with the clip is to pull extremely hard like with a side hammer. Usually the clip breaks when you do this tho. I bought a linkage kit from Speedway to do mine and it had all the parts in it including the little star. Don't know if this is what you were looking for but thought it might help.

 

Oj, he has it on the right pedal.

 

Ah, you're right! I was looking at it from the wrong side of the firewall. Thanks for that.

 

Can you mount the rod end between the 2 arms? instead of the out side?

 

I can mount it in between, and it lines up, but then there's no way to mount anything to the clutch arm.

I checked inside the MC bore and I can feel a little detent that'd hold the retaining clip. Do the push rods usually come with those. Any tips on where to find those? I looked all over and maybe I can't find them because I'm calling them the wrong name.

.

 

Having difficult time seeing why the offset to the bolt that you made, I think that the bore hole where the push rod goes in is at least an inch or so, brake pedal must have a stop so that it can not pull up towards the driver, you only need an 1/8 of an inch play from brake pedal at rest and contact to the master, if you make the rod it has to be fully rounded to prevent binding, hope this helps

 

Ideally, you would use a clevis instead of heim. By the time you add a large washer to safeguard failure, your outa room. I'd be biting the bullet and repositioning the master.

 

Yhea 3banjos, I have a clevis but that puts the angle even larger. I was thinking about moving the MC mount too to get it to line up, but I wanted to get y'alls thoughts before I start cutting.

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some master pushrods have a o ring to retain the shaft in the bore , the boot will have enough strength to hold it once you set the master up as you want a little pressure on the master cup but not enough to start blocking ports in it . the hydraulics will push back on the rod to keep it in place . on the race cars we put a tube a 1/4 bigger then the rod ID around the pushrod as a safety to keep it from "dropping out" but as for the angled pushrod , I do not like it , in a emergency situation the hard hit of your feet will make it bend at the bends when we have to make shafts like that we use 5/8 DOM tubing . and clevis's to keep it from rotating

 

Here is the cut-to-fit master cylinder push rod that So Cal offers


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I saw that one and length wise, it should work. But it's still a heim which would make the angle too tight mounting it as is I'd mounted on the outside of the pedal. I'm thinking the MC will have to be moved to get it lined up.

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If you took the clutch pedal off and slid the brake pedal over would a push rod be lined up straight from the pedal to master cylinder? If so does So Cal make two different K members, one for brake pedal only with auto trans and one for brake and clutch pedal with standard shift trans. Also if it lines up will clutch pedal mount on side towards frame? Are there a different set of pedals for what you are trying to do? Please post what you figure out. So Cal should build these to be bolt together.


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Take and tap the hole on the clutch arm, use lock tite & make sure the threaded bolt ends is flush or 1-2 threads to the inside. If you are worried it will back off drill a hole pependicular to the bolt and pin it with a roll pin.

 

That's a good question. I'll check this out!

 

I spoke to Ray at So Cal. He said they only make 1 version of that K member but the mounting pivot for the pedals is adjustable. The problem is it's only adjustable toward the inside of the frame, but it needs to go the other way to move the pedals a slight bit outward.

He also said that the pushrod they recommended is theirs with the heim on it, which has to be mounted on the outside. He said that the pushrod is supposed to be mounted at an angle, and there is no clip holding it in place (they usually make up some kind of stop to keep it from coming out).

So I'm thinking of moving the MC mount inward a bit to get it to line up. For the internal pushrod clip, I can fab up a pushrod that is located inside the MC piston bore and is clipped in place with something like this.

 

The stop could be the toe board (or something on there). Doesn't have to be at the master end because as long as the pedal travel (with body fitted) doesn't allow the inserted end of the rod to come out of the master far enough to drop out then there isn't an issue.

Have you seen one of these SoCal frames built up. There's a display model in Reids in Orange, next to CW Moss - might be worth a trip out?

Chris

 

Down here a brake pedal must not bottom out on floor boards first but the master cylinder, and brake rods must be straight with no bends. Offset pedals arms would solve your issue and align things. Double sheer is preferred and if not a grade 8 UNF bolt. Shift the rod to the other side as per post #12 and use a HT low profile UNF button head with suitable safety washers and a 1/2 nyloc nut to secure.

 

My Clutch pedal is countersunk for a corresponding bolt that can be used for the clutch linkage.
You should also be aware that SoCal positions the Clutch and Brake pivot about 1" higher than normal, because they raise their floor boards about 1".
If you are using the stock channel in the sub rail for metal floor boards and the stock location of the toe boards, your pedals will contact the intersection of the tow board and the floor board. This will limit the throw on the clutch and brake pedal unless this is addressed.
Lowering the pivot is the best way to cure this problem at this stage of your build.
A dual Master Cylinder will not work properly unless it can be fully stroked.

 

A lot of correct advise here for sure. It may be the picture but check to see that the pedal pivot is parallel with the M/C mounting flange. Being a little off on welding the pivot will create some unwanted angle.

 

So I went up to So Cal last week and spoke to them about this. They didn't really have a solution, which surprised me since they made this. It seems like this was designed for and auto transmission because the brake could be lined up properly. Anyhow, I think I may have found a solution.

I picked up one of their pushrods and bolted it between the two arms. It's not 100% perpendicular, but it's close. And it's a straight rod. For the clutch, I can weld a threaded stud to the pedal to connect to the clutch linkage, which solves the clearance issue. There's no way the pushrod can come out because it hits the pivot before pulling out of the MC

 

If you move the M.C. further rearward? so the mounting bracket is about where that sharpie line is drawn on the tube. It looks like the alignment would be improved.

 

The pict doesn't show it, but I can only move the mc back maybe an inch before it hits one of the main cross bars. So it doesn't give much more offset. Maybe if I we're to move that back a little, and trim the pivot mount to bring the pedal assembly in a little, that'll line things up a bit more.

 

Cutting the So-Cal mount off carefully right at the (nice) welds and sliding it back along the angled tube should give you the ability to run a straight pushrod to the M/C. It will take a longer pushrod, I made mine from a length of 4130 Chromoly tubing drilled and tapped for a heim on one end, and a pushrod made from a fairly long 3/8" - 24 aircraft bolt with the head cut off, and the end rounded, on the other end. The tubing can be bought from Aircraft Spruce by the foot. (posted this before I saw the OPs latest, about the movement being limited )