Glad I don't have a "blackboard" brcause it would be scribbled on something terrible-LOL So Blue Bird, if you will try this link I think this guy does as good a job on explaining it as I can. Ken may come in here if he sees this but just pay him no never mind-LOL. Here is the link
Explanation on how a tach works


Oly in Oregon

Rest in Peace

1945 GMC COE Victory Truck
1953 Willys CJ3B
1955 Chevy 1st series 3/4-ton
1958 WIFE Last series

Never say "Whoa" in a mud hole