Why does the car have a Rough Idle?

Assuming you are talking about a "rough" idle that reads around 500 to 700 RPM on the tachometer, Welcome to the World of Longer-duration Camshafts and V-10s! Your rough idle is actually normal. First of all, the Vipers V-10 motor has 10 cylinders firing onto a 90-degree crankshaft, which means it has an uneven firing interval for two of the ten cylinders. In other words, the spark plugs DO NOT all fire in equally spaced time intervals. So thats one cause of an un-smooth idle. Secondly, the camshaft duration is 220 degrees (@ 0.050" lift), which translates into a motor that prefers to spin happily (and efficiently) an higher RPMs. And, subsequently, does not operate very "smoothly" at low RPMs.

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