Is the clutch failing?

[FiatJim]

When driving my 73 spider up a fairly steep hill, at a modest spirited pace in 3rd gear, the car began a slight stumbling movement. The longer it went, the more violent the stumbling, jerking,.... it became. It got bad enough that the tires were chirping. The sensation was rhythmical and reminded me of a springing trampoline. I shifted into fourth, it went away. It seemed like the problem only happened when driving up a hill, in third gear at about 30K rev. The tach does not waver at all when this is happening. However, when I next drove the car, the problem was felt in 2nd, 3rd and 4th. The clutch parts are new,.. BUT they came with the car when I bought it and I have no idea as to the quality. I had a very competent, Fiat shop put it in.

Would a failing clutch (torsion springs) make this happen?

[So Cal Mark]

nope, not a clutch issue. Symptoms like that on a hill are usually related to fuel starvation

[FiatJim]

Thanks Mark. The problem has been getting progressively worse during 2-3 hours of drive time. Also, the car now stalls when coasting. Fires right up. Would changing the fuel filter be a good place to start?