340 Gets Terrible Gas Mileage

RustyRatRod said

That valve is a delay valve for the vacuum advance on the distributor. I would bypass it and run the vacuum line straight to the vacuum advance from the carburetor. It is an emissions device designed to lower tailpipe emissions and is not conducive to performance.

But that valve is not your problem. Check the initial timing and report back with where it is.

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Hey Rusty I tried to check the timing. Car idling at 850 - 900 rpm with the vac gauge hose plugged. #1 cylinder is on driver's side first cylinder closest to front of car, right? The timing mark does not show up on the timing tab. The timing tab ranges from 10 before and 10 after with 10 before at the top of the timing tab as I look down on it with my timing light. I can see the crank pulley a fair bit below the 10 after mark and I do not see the mark on the crank. I cannot see much above the 10 before mark due to water pump in way. I must then assume that the initial timing is in excess of 10 before. My timing light is old (40 years old) and has not been used in awhile but does this tell you anything?

Thanks

Dave