55.2-59 Classic Industries Undermount Master positioning

[unclebrad]

Back in the summer, I had M2 suspension added to my truck. This included replacing the Brake Master, which is from Classic industries, to go with the disc brake setup. I recently took the engine out and to the machine shop for some serious work, and have been cleaning up the engine bay while I have good access.

I noticed that the Brake pedal arm in out of it’s original position, rubbing against the hole in the firewall, and is also pinning the brake switch arm to the firewall.

None of this is hindering the function of the parts, and it looks like the master is mounted properly but, being a little ocd, I don’t like it and want to get it into the right position.

Any thoughts about how I might remedy this? (Not about my personal issues. ;-))

[Hcb3200]

yep stock has a rubber piece of the switch arm. any piece of hose will do. you may need to adjust if the hose is too thick.

[Hcb3200]

the rubber acts also as a cushion. to help limit the shock on the switch when pedal returns. I went thru a couple of switches before I put the rubber piece on and have not had issues since.

[nvrdone]

The brake light switch is one issue that looks like it's been solved.
The other issue you mention is the brake pedal rubbing on the side of the hole. Looks like an aftermarket pedal. I would check the cab mount bushings. If the cab is moving side to side it will cause the pedal to bind. If that's not the problem iI can think of three solutions.
First, open up the hole with a rotary file so the pedal doesnt contact the floor. second. see if there is any adjustment to move the pedal a bit to the left. Third, if the m/c is mounted to the original frame bracket, try shimming the m/c to the right on the back bolt, pivioting the pedal away from the side of the hole. Hope this is clear and helps. Good luck.

[mr48chev]

This gives instructions on how to center the pedal in the hole.

[dsraven]

I gotta say first, check the pedal arm pivot bushings to ensure they are not sloppy and allowing the arm to move side to side. it's a long lever so a little play in the bushing can make a lot of movement at the business end of the lever.
next, not a bad idea to check the cab mounts, fore and aft, and also the sheet metal of the cab in the area around the front hinge pillar and the "sandwich" of steel at the rear cab mount/cab floor. they are known areas of failure from rust. repair any issues you find and possibly even replace the rear rubber cab mounts if they look packed down or if the rubber is cracked. the factory assembly manual has a dimension for clearance from floor to frame that you could check also. then level up the cab to the frame by shimming the front mount but do this in conjunction with the rad support mounts. check or replace the rad support mounts as they work in conjunction with the cab to support the front fenders and make things sit level and ensure the body lines all line up. this is done by shimming the rad support mounts and/or the cab, with the fenders on. I like to use a couple of pieces of tape across the body lines at the foreward and rearward end of each panel, use a pencil or dark pen to mark the center of the body line at each piece of tape. then I use a couple of magnets, one at the forward end of the front fender and one at the rear of the cab, to hold a string line that can be pulled tight and spaced off the cab slightly. this will quickly show you if the body lines are lines up because the string should be lined up with each of the pen marks on the tape. shim accordingly to get the body level. the cab can also be turned slightly on the frame to allow for better hood gaps at the cowl, if your hood gap is not equal or the hood doesn't fit well in between the fenders or if youre having trouble getting the door gaps to fit the same side to side. there are a lot of variables when assembling these old trucks and the gap issue was not really an issue when they were built, as long as the doors and hood closed and the dog wouldn't fall through the gap it was all good, haha.
I think one forward cab mount hole (in the cab structure) is smaller than the other so use that as the pivot point to turn the cab slightly on the frame if required. here is a link to a video that shows a guy explaining how he did this on his 4 eyed version. the pedal should definately not be rubbing on sheet metal as that can have enough drag so that the pedal doesn't fully return. if that happens it can cause master cylinder/brake issues. if the pedal can't return fully, with a little slack in the linkage, then the system can't fully let the pressure out of the brake lines when the pedal is released OR allow the master cylinder to "refill" the master cylinder bore as it needs to. if the master was replaced all the linkage pivots and bushings should have been checked/rebuilt. if nothing was bent or "adjusted" to be different than stock, as far as the pedal arm and linkage is concerned, then i would say your cab has moved somehow so you will need to dig into the "why" of that. likely not too serious by the look of the condition of the sheet metal in the pic. one other point that can affect the cab mounting is whether or not the stock transmission mount was removed. if so, that is what held the frame rails at a certain dimension apart and removal without a new support can allow the frame to move in that area. this can be bad for cab mounts andsomething bad for cab mounts can have an affect on door opening/closing, fender to door gaps, cab cracking near the cab mounts, etc etc
anyway, here is the link if you wanna check it out
https://youtu.be/RgUwd9PdWiA?si=C0tltLtn8lc4FA7p

[unclebrad]

Wow! Lots of good advice. Thanks!

I will have a little time to crawl around and look things over today, with this stuff in mind.

Hopefully, I will report back having found the culprit.

BTW, I found this pic from some time before the M2 project, that shows the arm centered in the hole, so I am guessing it isn't a cab issue, but an issue with the master cyl installation. The pic also shows that the brake light switch has been hitting the firewall (paint chipped there) so that isn'tnew, just something I noticed only when I was looking at things more closely.