A 396 GM engine was troublesome in the early years due to valve train issues. My first new car was a 67 Satellite 383 4-speed 3:23 sure grip. My best friends car was a 66 Chevelle 396 325 hp, 4-speed with whatever Chevy had for a standard rearend ratio, I believe 3:31 or something which was a little lower than my 3:23. He had had his car about 6-7 months prior to me getting mine. I show up at the local hangout one evening and so does he. He asked if I had my car broke in. I said, it's about as good as it gets, so we go up the road for a match race. My car still has the factory provided 775-14 skinny tires, he's already worn out a set of tires and has upgraded wider rubber. We ran the quarter 3 times that evening and I won by 3 or more car lengths all three times. First run he claimed he went up in smoke. Second run he claimed he missed a shift. Third time, I didn't hear a excuse, because I didn't see him until a week later.