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Well, the experiment is over, and I am back to 4 valves / cylinder. I was uncomfortable with the pinging, which occurred under almost any load. The return to stock got rid of the pinging.
As I said, I had been hoping for an increase in low-end torque, and that was not a result. There was a decrease in power. I believe this decrease in power was also responsible for negligible fuel economy increase. I had to use more throttle than before to accelerate.
One of the clear changes was less valvetrain weight and resistance. The engine revved easier. This was bad in terms of hitting my 3k RPM max shift point (with lesser power) and for the auto transmission, which seemed a little "confused" at times. But the benefit was to idle and cruising, requiring less power for both events. As a highway-only car, this might be a good mod. Combined with the acceleration deficit, the overall results seemed negligible, as I said.
That said, the economy results are hardly scientific. I ran the 3v setup for half a tank, and it's a good tank. That said, there are too many variables. 1) It was much more highway than usual. 2) I'm running Shell 93 in an attempt to combat the pinging. 3) I got a flat tire and swapped on a set of alloys over the stock steel wheels. 4) I removed the spare tire and tools after the flat, decreasing weight.
So my "results" are based solely on keeping a constant eye on the ScanGauge. Idling required 1hp less - a good indication of the decreased resistance - though MPG is still 0 in that situation, obviously. Highway readings seemed 1hp lower and 1mpg higher at 55mph than my usual.
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