What's happening?
Find out in
THE SHOPS !
Genearl Truck Talk
20,267 threads; 177,521 posts
The Engine Shop
32,460 threads; 255,065 post
Driveline
8,796 threads; 65,970 posts
The Electrical Bay
9,505 threads; 74,285 posts
Sub: The Radio Bench
The HiPo Shop
5,040 threads; 46,029 posts
Paint & Body Shop
12,505 threads; 81,120 posts
Sub: The Doors
Interiors
4,059 threads; 26,817 posts
The Tool Chest
1,762 threads; 26,817 posts
Making a Stovebolt Bed
1,052 threads; 6,659 posts
|
|
|
Forums59
Topics128,597
Posts1,041,768
Members46,055
| |
Most Online1,229
Jan 21st, 2020
|
|
|
|
Joined: Mar 2010
Posts: 10,155
'Bolter
|
Aren't you using the original brake pedal arm and doesn't it hit the lower toe board to stop it's travel? What's the difference between now and when it was a single pot MC? The pedal/arm has to return and bottom out against something so you can adjust the rod to allow the MC piston to fully retract. Mike B  The original brake pedal arm does not hit the toe board. It is held at a specified distance from the toe board by turning the threaded clevis thus adjusting the length of the pushrod. The problem the OP is having is that, unlike the original master cylinder, his Corvette master cylinder does not have a captivated pushrod. There is nothing to prevent the brake lever return spring from pulling the Corvette pushrod out of the master cylinder.
|
|
|
|
|
Joined: Mar 2004
Posts: 5,538
'Bolter
|
The original brake pedal arm does not hit the toe board. It is held at a specified distance from the toe board by turning the threaded clevis thus adjusting the length of the pushrod.
The problem the OP is having is that, unlike the original master cylinder, his Corvette master cylinder does not have a captivated pushrod. There is nothing to prevent the brake lever return spring from pulling the Corvette pushrod out of the master cylinder. So if I understand right, the AD trucks have a washer/clip on the rod inside the nose of the MC to keep the rod from pulling out...that's the stop? If that's right then he will have to fab up a bump stop on the toe board. Thanks Carl! Mike B
|
|
|
|
|
Joined: Jun 2019
Posts: 151
OP
'Bolter
|
So if I understand right, the AD trucks have a washer/clip on the rod inside the nose of the MC to keep the rod from pulling out...that's the stop? If that's right then he will have to fab up a bump stop on the toe board. Thanks Carl! Mike B After doing some digging, I found out a couple things about the original AD master cylinders. First, the piston end of the push rod is ball shaped (not just round on the end), and 2.) the end of the master cylinder has a sheet metal plate with a hole in the middle that the push rod passes through. This plate is held in place by a wire spring clip. So, the push rod is captured inside the master cylinder housing between the piston on the end plate. This set up is what makes it possible to adjust the position of the brake lever by shortening/lengthening the push rod at the clevis. As 52Carl pointed out, the Corvette master cylinder does not have a captive push rod. Because of this, shortening/lengthening the push rod does nothing to change the position of the brake pedal lever. The lever goes all the way up until it hits the brake light switch no matter what. You still have to adjust the length of the push rod to take up the lost motion at the master cylinder so that your pedal works sooner than later. At this point I think the easiest solution to my situation would be to buy one of those rubber bumpers that goes on the clutch arm, then cut one end down so that it sets the arm at the required 13/16" from the toeboard. I thank and appreciate everyone's input on this thread.
Brian
'51 Chevy 3604 Project
'28 Chevy LO basket case
'83 GMC Sierra 4x4
|
|
|
|
|
Joined: Jul 2000
Posts: 1,538
Insomniac
|
The 'required 13/16"' applies to the original m/c. This no longer applies now that you have changed it. I'm much closer than that.
Gord
----
1954 1/2 ton 235 4 speed
|
|
|
|
|
Joined: Mar 2010
Posts: 10,155
'Bolter
|
The 13/16" gap sure would work nice for the original brake light switch.
|
|
|
|
|
Joined: Mar 2004
Posts: 5,538
'Bolter
|
After doing some digging, I found out a couple things about the original AD master cylinders. First, the piston end of the push rod is ball shaped (not just round on the end), and 2.) the end of the master cylinder has a sheet metal plate with a hole in the middle that the push rod passes through. This plate is held in place by a wire spring clip. So, the push rod is captured inside the master cylinder housing between the piston on the end plate. This set up is what makes it possible to adjust the position of the brake lever by shortening/lengthening the push rod at the clevis. Your description is what I was thinking about...we're on the same page now! Whatever you make for a bump stop it needs to be robust enough to never fail allowing the rod to suddenly pull out...rubber could squeeze out or collapse over time. Mike B
|
|
|
|
|
Joined: Jun 2019
Posts: 151
OP
'Bolter
|
The 'required 13/16"' applies to the original m/c. This no longer applies now that you have changed it. I'm much closer than that. The 13/16" dimension, per the Factory Assembly Manual, is from the pedal arm to the toe board. I'm guessing that is the recommended clearance for the pedal arm to properly operate the brake light switch?
Brian
'51 Chevy 3604 Project
'28 Chevy LO basket case
'83 GMC Sierra 4x4
|
|
|
|
|
Joined: Jul 2000
Posts: 1,538
Insomniac
|
I use the factory switch. Seems to work OK. 
Gord
----
1954 1/2 ton 235 4 speed
|
|
|
|
|
