Here is something interesting. A stock 340 4 speed cam (268/276) had 44 degrees of overlap. My roller cam has 41 degrees of overlap instead of 8. I used the wrong duration numbers to figure it. So this explains why I get 155 psi cranking compression with a 10.2 to 1 calculated compression ratio. Dave is right I'll be giving up some gas mileage, but hopefully not too much.I'll just have to drive faster to get the engine in it's efficiency range. Then the air drag will kill me Still it should give at least 20 MPG