[DavidNJ]

One look at the spec sheet shows modern engines are more powerful, more fuel efficient, smoother and better running. The next question is why.

First, they have better combustion chambers, something your 1969 head won't have.

Second, they have port fuel injection, usually with a mass air flow sensor. Again, something you don't appear to be doing. This probably should be expanded to the ignitions, which are also controled by the ECU.

Third, they have cams that take advantage of everything they can. More aggressive lifts. More lift. At .200, some luxury sedan cams look like a '60s performance cam. While being much smaller on the seat. New valve spring and rocker arm technology is required to enable this. Not just a roller, but a low inertia roller.

Fourth, they are using separate intake and exhaust cams with variable cam timing. That is why a 350Z is as quick in the 1/4 miles as a 427/435 Corvette in 1969. Or a Twin Turbo Supra in 1994.

My first car was a Boss 302, purchased new as a leftover in 1971 (for $2950). Rated at 290hp and about 3200# (if my memory is correct), C&D timed it at 14.9@92 in the 1/4 mile. About the same as a Honda Accord or Hyundai Sonata today.