I purchased and installed an automobile tachometer. We have a K241 with a K301 block bored out .020 over. At idle speed how many r.p.m. should I see on the tach ? Other than the boring done because of cylinder wall wear, the tractor is stock...running at full throttle, what kind of r.p.m. should I see ? I wnat to try to determine if the tach is working correctly