Fuel Air Spark Technology - Better Breathing Exercise

The FAST meter can be mounted to the dashboard using Velcro strips, but for our purposes, as we were not actually driving the truck on the street, it was simply hand-held while Ernie "drove" the pickup. I have very low gearing in the rearend, so our tests were run in second gear in order to reach 4,250 rpm without reaching speeds of way over 100 mph!

In most cases with normal gasoline, an air/fuel ratio of approximately 14:1 (14 parts air to 1 part fuel) is considered ideal. A mixture less than that (12:1) is considered rich and higher (16:1) is lean. Our first dyno run revealed a maximum torque reading of 211lb-ft at 3,350 rpm and maximum power of 154.1 hp at 4,200 rpm. These corresponded to road speeds of 64 and 84 mph respectively, in second gear. More importantly, the FAST meter showed a ratio of over 14:1 below 2,800 rpm, 13.1:1 at just under 3,000 rpm, dropping to under 12:1 at 3,600. 154 horsepower doesn't sound like much, though that was measured at the wheels, and the guys at Westech said they'd seen power losses of up to 80 hp through TH350 transmissions. Okay, so I'm disappointed, but it's only a stock 305.

In a bid to improve the air/fuel ratio by making the secondary jets smaller, and hence leaner, Ernie decided to replace the 68 jets with a pair of 65s, which is as easy as removing the rear float bowl. It was full of gas so Ernie removed one of the lower retaining bolts and drained the gas through its hole into a receptacle first.

With the float chamber removed, the secondary metering block was gently pried from the main body in order for the jets to be swapped out.

With everything buttoned back up, Ernie took the pickup for another "drive," resulting in a leaner air/fuel ratio for most of the rpm range and slightly better peak torque and horsepower figures. This time we saw max torque of 215 lb-ft at 3,400 rpm and peak power of 156.9 hp at 4,269 rpm. The FAST meter indicated an identical 14:1 ratio below 2,800 rpm, a slightly richer 12.4:1 at 3,000 where previously it had been 13.1:1, 12.7:1 at 3,300 and never dropping below 12.4:1 again throughout the entire range up to 4,300 rpm.

Overlaying our two runs in graph form, it illustrates our slight gains in horsepower and torque