340 Gets Terrible Gas Mileage

MopaR&D said
I think he means to use it just for the sake of figuring out the cam timing events turning the engine over by hand, not necessarily leave it on the damper permanently to use when the engine is running. It would save the hassle of removing the pulleys and crank bolt to attach a degree wheel.

yes. Exactly.

MopaR&D said
I have a cheap unknown-brand converter in my Duster that stalls around 2600 RPM and is pretty loose in street driving but I still average 14-16 MPG with a 450 HP 360 although I do have 2.94 gears. Still I think even if I had 3.55s it wouldn't be much worse.

Yup. I had 3000 brake stall setup and had T/A adjust it down a few hundred rpm. But regardless, higher stall speeds do not directly equate to slipping for normal driving. Under light throttle there's no slippage worth worrying about. Its under full throttle that it slips up to the stall speed. More power can drive the stall speed up. Less power drops it down.

FWIW that car got 14.0 mpg in normal mixed driving. With recreational use, 1 autocross per tankful, usually around 9 mpg. City only driving, its more about gallons per minute. When a car's not moving fuel use is all about time running.

I've got to say that I don't believe spark plug brand is going to make a noticible fraction of a difference to power or mpg. If a plug is cracked or damaged, then its bad. If its fouled, its fouled. Sure NKG's quality may be better than Champion's. But if someone wants to buy me a set, I'll run them back to back against the Champions at the track. If the MPH goes up in a meaningful way, I'll pay for them. Cecil, maple Grove, or even ATCO if we could somehow be sure of getting more than 1 run in 4 hours. Need at least 2 runs on each set.