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54/K, .200" wide fuel ramp. We make a variety of ramp widths and depths, with various rates of ramp depth taper. What works well for a drag racer may not be correct for a road racer. The correct spool for an application is the one that delivers the proper amount of fuel at all the part throttle opening angles. The correct spool for an engine equipped with a 2-1/16" injection manifold is probably not the right one for a similar engine with a 2-1/2" injection manifold. The air flow increase per degree of throttle rotation using the larger throttle will be greater than that of the smaller one, therefore requiring more fuel per degree of spool rotation. Most of our competitors spools work well at idle and wide open throttle, but do not provide the proper amount of fuel at part throttle. Since the ramp is fixed, the only way to achieve the fuel required at part throttle with one of those spools is by richening the idle, which advances the entire ramp. Unfortunately, the idle is now too rich. Plug fouling and engine stumbling may occur.