I asked this question on another forum and got 1 reply. But figured I’d ask the Moparts crowd as well. I finished my Duster V8 4 speed swap and am
Putting miles on it. I noticed a little normal engine vibration and harmonics coming through the clutch pedal at say 2200+. This is my 1st old car manual. So I’m not sure what’s Normal and what’s not. I have a Ram B&B style clutch and all from Brewers. I have about an 1” of free play and .065” of air gap. I’m not riding around pushing on the throwout bearing but I am trying to diagnose this. I noticed the free play is easy like one would expect at 2000 rpms and lower. Around 3000 rpms I noticed the free play was much stiffer at higher rpms. The free play amount was the same, just a lot stiffer. You could rest your foot on the pedal and every single time when it gets down to 2,000 rpms the pedal will easily fall to the end of the free play. So whatever this is is almost like it’s pushing back on the pedal at 2,000+. What have I not got adjusted correctly here?

It could be the engine torqueing up on the left side causing a change in the linkage alignment. That's just a guess so take it with a grain of salt.

It sounds like the clutch pressure plate fingers are extending more from the weights on the fingers above 2200 RPM
I would adjust clutch rod out some more to raise the pedal up so you have very little pedal free travel before it starts to disengage the clutch to see if that is what is going on
All the OEM Dodge and Plymouth 4 speed cars I've owned and raced needed very little pedal travel to get them to shift easily Maybe a 1/4 inch of pedal movement from the top to get them to shift without dragging the clutch throw out bearing on the fingers

I don’t see how the clutch adjustment rod would have enough force to bend the pedal stop inside the car. The pedal is spring loaded all the way back as it is. I adjusted some free play and we will see.

Something is enabling the fingers on the PP to come back against the throwout bearing. I can’t even understand this. Surely to god the crank doesn’t have .500” of runnout.

Which type of clutch pressure plate did you get? Borg and Beck, Long or centrifugal ? The throw out bearing must be at least .100 from the fingers of the clutch pressure plate with the clutch pedal all the way up as far as it will go with the motor shut off
Old Mopars cars have used more than one throw out bearing over the years, getting the correct one, proper length, is needed to get the clutch pedal adjustments correct
If yours is touching the finger with the clutch pedal up all the way up now(don't drive it anymore ) take it out and see if you can get a shorter one
Let us know what you find and do, this will help others on here down the road

This random guy describes exactly what I’ve got going on. I guarantee this is the problem now. I have a RAM Borg and Beck and disc from Brewers. They are very helpful people and even they are at a loss of what’s happening. Watch this. https://youtu.be/QJuJ3CEhZtA

By the way, I put 1/2” of bearing clearance and 4” of free play just as a test. It’s better, but it’s still touching the bearing. Plus it’s not practical or drivable. Just did it as a test. This is exactly what I’ve tried to describe.