[Tommy]

J.
Here's a non-technical answer. If you have a very modern engine with computer controlled direct injection fuel system, variable valve timing, a seven speed transmission, etc., you can have the best of all worlds. Look at the newest Corvette for an example. It has astonishing acceleration, near 300 KPH top speed, and gets reasonably good gas mileage running on only four cylinders when cruising. ... But, if you want to spend a lot less and get a good daily driver that gets good gas mileage but not much in the way of high performance, you can do that by optimizing a small engine to do that one thing very well.

The "hot cam" issues I suspect you are asking about regards the 1960-70 vintage American V8 engines commonly used by many of us with Cobra replicas. Most of these are not sophisticated engines in the modern sense. They can be optimized however you want, but most of us get some variation of the big horsepower version. That means they run very well at high RPM and near wide-open-throttle settings, but not so much at low RPM cruise settings. We could make them more friendly to stop-and-go traffic and low speed cruising if we wanted, but it would be at the cost of the some top end performance. And you seldom see anyone proudly putting their MPG after their signature on this forum.

The last thing I'll offer is that by choosing an older engine design with a cam that is optimized for high RPM, full throttle operation, you get an engine that runs a little uneven at idle. For Americans of my age, that sound is synonymous with the highest performance engines of my youth. I understand that there are smoother running engines today that greatly outperform my engine, but they just don't sound as good to me. It's a personal taste thing, and the sound of my car is just about my favorite thing about it.