63 Master Cylinder measurement

[Steve D.]

This is related to another thread _ "C2 brake saga revisited"

I'm chasing a brake pedal travel problem that has come down to a geometry issue. I have excessive freeplay (1.25" compared to AIM spec of .06" - .25").

Does anyone have a 63 master cylinder on the bench that they can take a measurement on? The deminsion I need is from the face of the MC that abutts the firewall, to the back of the depression in the piston (where the push rod contacts the piston).

As noted in the other thread, this is the last place to look for a change in geometry.

Steve

[Steve D.]

Re: 63 Master Cylinder measurement

I actually need two measurements: 1) from the edge of the opening in the rear of the MC to the back of the recess in the piston and 2) from edge of the opening to the back of the mounting flange (flange face that abutts the firewall).

The extra 1" of pedal free play is the result an extra 1/2" of rod free play. The object of the measurement exercise is to try to determine where the extra 1/2" is being introduced.

[Edward J.]

Re: 63 Master Cylinder measurement

Steve, I don't have the measurments,but , pedal travel is not always a rod adjustment , sometimes things like brake drums that may have been machined out of spec.s. this will cause the pedal to have excessive travel,even if the adjusters are turned out to meet the drum, this will only be part of the equation, the upper wheel cylinders will have to travel out to meet the drum,having the drums close to spec.s help pedal travel and feel.

also knowing that the sytem is properly bleed, and shoes adjusted to slightly drag against drums is always important.after all this is meet ,the rod adjustment is something to look for lastly.

Last summer I rebuilt a friends 63 brake system and had quite the time removing the air from system.

[Chris D.]

Re: 63 Master Cylinder measurement

Steve,
I don't have a master cylinder off the car but I do have an original push rod and a know to work piston.

The rod length is 4.12" overall with 1.2" of that threaded (3/8" fine thread as noted earlier).

When inserted into the piston, 2.47" of the rod extends beyond the rear surface of the piston.

While this does not get you all the measurements requested, it does let you check to see if the rod and the piston are causing your problem.

Just for grins, I scaled some approximate measurements from the cut away picture in the shop manual. In the old days of pencil drawn design prints a standard warning stated "DO NOT SCALE". That advise applies here so do not make any decisions on path forward without confirmation of actual part measurements.

Looks like the dimension from the flange mounting surface and the back end of the casting scales 0.65". The dimension from the rear of the casting back into the bore to where the piston meets the snap ring scales 0.10"

Does any of this match what you have?

Chris.

[Carl S.]

Re: 63 Master Cylinder measurement

The distance from the the bottom of the piston to the casting top is 1.812". The distance from the casting top to the mounting flange is 0.556 and the distance from the casting top to the recess for the fire wall seal is 0.684". I hope this helps you out. I just painted it after rebulding it yesterday. so it was right there for measuring.

[Jack Y.]

Re: 63 Master Cylinder measurement

I'll just mention this as I had a pedal travel issue with a car I bought and it drove me crazy. I found that someone along the way had reversed the rear self-adjusters and installed the left on the right and vice versa. It was a Chrysler product but the point being, the correct assembly at the wheel was critical to the pedal travel. Good luck.

[Steve D.]

Re: 63 Master Cylinder measurement

Chris

Thanks, I haven't made my measurements, but will tonight. I did, however, fabricate a slightly longer rod from a 3/8" bolt (proper credit to Mr. Hanson) and it solved the problem. I will post the measurement comparison tonight.

Steve

[Steve D.]

Re: 63 Master Cylinder measurement

Carl

Thanks. Timing is everything; glad I got my post in before you re-installed it.

Steve

[Steve D.]

Re: 63 Master Cylinder measurement

Chris

My measurements are very close to yours and Carl's, so I still don't know where the extra travel is created. But, the good news is that the slightly longer rod allows adjustment to eliminate the excessive free play and get a solid pedal without excessive pedal travel.

Steve

[Michael H.]

Re: 63 Master Cylinder measurement

Chris

My measurements are very close to yours and Carl's, so I still don't know where the extra travel is created. But, the good news is that the slightly longer rod allows adjustment to eliminate the excessive free play and get a solid pedal without excessive pedal travel.

Steve

Steve,

By chance, did you look at the rubber up stop bumper for the pedal to see if it was complete and in place? Just a thought.

[Steve D.]

Re: 63 Master Cylinder measurement

Michael

Bumper stop is in place and brake pedal at rest is even with clutch pedal.

[Boyan B.]

Re: 63 Master Cylinder measurement

Can I get the measurements for the new fabricated rod? I am having the same problem with not enough travel.

Thanks,
Boyan

[Steve D.]

Re: 63 Master Cylinder measurement

Boyan

I just added 1/2 inch, so my fabricated rod is about 4.625 in. As noted before the thread is 3/8" -24 (fine thread).

Steve

[Kenneth S.]

Re: 63 Master Cylinder measurement

Steve,
You mentioned earlier that your brake pedal is now even with the clutch pedal. Do you have Power Brakes? On my '63 with PB and 4-speed, there is a significant difference in the two pedal heights.
Ken

[Steve D.]

Re: 63 Master Cylinder measurement

Ken

I do not have power brakes.

Steve