Hello, I have a 1981 CJ7 Laredo

Hello,

I have a 1981 CJ7 Laredo. It came with a 2.5 4l engine out of the factory, but the last owner instaled a Chevy 283 from a Corvette in it. It also has the hidraulic clutch, and now im having problems with it. (FYI, the bellhousing its a perfect match for the chevy small blocks, so im using the original transmission SR4+dana300). I already changed the Clutch Master and Slave cylinders. The problem its that sometimes, after a bit of overrev, the clutch pedal will get really hard to push, and it wont come back when you release it. You can set on the gear, but the Jeep wont move or move too slow and with a lot of engine revs. The only way to keep going its to bleed the system and then the pivot that goes into the bellhouse will make a sound like its loosing and come back to its normal position. After that, the jeep drives if nothing happend. What could it be?