Most of you guys don't understand that an overdrive transmission and hot cam DO NOT GO TOGETHER. You have never seen a rump-rump cam paired with an OD trans from the factory and you never will, because the factory engineers know that a rump-rump cam has an operating range of rpm's that is much higher than the rpm's of the motor while using 4th gear overdrive. If the motor is taching 1800 at the crank, for instance, and the cam has been designed to operate efficiently from 2800 to 6000, then the crank is 1000 rpm's out of phase with the cam. Likely, the motor would not pull the hat off your head at 1800 and fuel efficiency would be in the toilet. So, what is there to gain????? If you want a hot rod that is fuel efficient ----AND FAST----, then choose a short cam like the factory would use and bolt on a turbocharger, blower or N2O so you can still go fast when you want to. BUT DO NOT BUILD THE MOTOR NATURALLY ASPIRATED WITH A HOT CAM AND OVERDRIVE. It won't work. Of course the car will still drive down the road, but it will not be efficient for speed nor mileage.

If you are building for fuel mileage, then use a cam that begins its operating range 500 rpm's before your cruise rpm's, to give the cam a chance to get "up on the tire"........ For instance, if you want to cruise at 1800, use a cam that has an operating range of maybe 1300 to 4800. By the time the crank gets to 1800, the cam will be in its range of efficiency by 500 rpm's and all will right with the world.

On the other hand, if you are building naturally aspirated to rip the tires off the vehicle and don't give a hoot about mileage, then for heaven's sake, use a 3-speed auto or a 4-speed that is 1:1 in top gear and match static compression ratio to the intake duration @0.050.....See the chart here.....
http://www.crankshaftcoalition.com/w..._compatibility
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