Vibration after open track with FFR

[mj_duell]

Hi Guys,
I have a problem I am trying to get nailed down on an FFR I recently acquired. The car is a Mark II with a three link rear and the build quality is excellent. The engine is a supercharged 5.0 and the tranny is a T-5. Last week I took the car to an open track event at Watkins Glen. It ran great all day with the exception of a leaky radiator cap, which I replaced. I ran the car fairly hard and found it handled very well and I was able to get a lot of speed out of it. Here is the problem. I was on my last run of the day on the third lap when I started to experience a very heavy vibration, which follows with rpm, from the front of the car. This vibration would go away when I pressed the clutch pedal and disengaged the clutch. It would come back immediately when the clutch was engaged. I could not figure out what the issue is. The car starts, idles and response smoothly when parked and in neutral or with the clutch disengaged. However, the vibration sets in when moving in gear and turning rpm’s above 1900. I have checked the usual suspects, driveshaft bolts, engine mount, tranny mount, header bolts, wheel lugs. It could be the clutch, but I am not getting any slip or engagement problems. Any ideas or questions that would help me figure this out would be great.

Thanks,

Mike