My /6 is a gas pig when it's cold outside. Why?

I had a /6 in my '68 for a decade. It was a smooth running motor stock, but I had Doug Dutra rebuild it using the smaller of his two spec'd cams, his Dutra Duals bigger valves, ported and significantly decked head. This deepened and broadened the midrange power significantly with only a mpg or 2 penalty in fuel mileage.

Slants and V8's love more initial timing, but are not tolerant of excessive total timing. It wasn't until I advanced the timing until the rpm stopped increasing(maximum vacuum) and limited the amount of total mechanical advance that it really woke up the motor. With my modifications, the initial timing ended up at 22 initial and 32 total. I then hooked the vacuum advance up to manifold vacuum and it advanced the timing even more at idle(but this does not increase the idle).

Once set-up like this, the car was dramatically more powerful off idle, would spin the tire out of the hole and got those 1 to 2 mpg back. This is the same technique that I use on all my V8's with distributors. The concept being that as you depress the gas pedal, the timing falls back to your initial settings reducing the tendency to detonate or ping while giving you more power right of idle and through the midrange. Max power output is not affected as the max timing is set by your total timing.

I now have a stroked 5.9 Magnum in the car. If driven like a normal person, it gets better mileage in the city and on the highway, runs and sounds way WAY better and is much more fun.