For starters, in 2012, I converted my '81 to a hydraulic clutch and an NP-435 transmission. When I did, I installed an entire clutch kit (flywheel, clutch, pressure plate, throwout bearing, and pilot bearing). The clutch worked beautifully, and I've been driving it for 4.5 trouble free years, and probably have 25,000 miles on it.
A few weeks ago, I installed the new engine that I built (build thread here: Performance 300 Build
With it, I again installed an entirely new clutch kit and flywheel.
However, after about 200 miles on the clutch, it has really started to stick. When I press the pedal to the floor, there's a groaning/creaking in the first inch or so of travel when I let off the pedal. Sometimes it binds so badly that the pedal doesn't even come up at all and it will just stay on the floor. I have to pull on it with my foot to get it free.
Here's the weird thing though.
There is no binding when the engine is off. It's nice and smooth.
It works perfectly the first 5 minutes or so that I'm driving and has plenty of travel and is nice and springy.
It slowly starts to get stickier and stickier the longer I drive. After 20 - 30 minutes of driving, it becomes really difficult.
Any ideas? I've never dealt with an issue like this, and I can't figure it out. It's becoming downright dangerous.