This is especially true if you aren't aware if all the possible causes of a problem. Chevy Big Block V8. Any info would be greateful. When the idle is right (AFR) the engine will tell you, listen to it. Instead of the relatively benign power produced off idle by your stock ECM, our optimized tune will plant you hard in your seat and give your tires a workout. 2L performing the way you want, Our extensive and proven range of camshafts are all available, with your choice of valve springs and timing gear/chain options to suit your application. A well honored starting table, as contributed by a fellow HP Tuner Forum member is: Valve overlap Idle RPM