The E85 Solution

Air/Fuel Ratio Chart
This accompanying chart offers comparisons of E85 and straight ethanol (or Jack Daniels, if you prefer), to gasoline. Stoichiometric is the term used to refer to the chemically correct air/fuel ratio that also creates the least emissions. This is also the air/fuel ratio most production engines are tuned to achieve at part-throttle. A leaner fuel mixture can generate better mileage, while a fuel-rich ratio generally will make more power by ensuring most of the air is used to create power.

By reading this chart, you can see that the air/fuel ratios for E85 are substantially richer than for gasoline from a percentage standpoint. What we found on the dyno was that we needed to increase E85 fuel flow through the carburetor by roughly 30 percent compared with gasoline. In a fuel-injection system, this could have been easily accomplished by merely increasing the volume of fuel flow (using the base fuel map) by one-third. This is a rough rule of thumb, but we found it to be pretty close for the purposes of our testing.

Engine Anatomy
Since everybody knows that small-block Chevys grow on trees in Southern California, we stopped outside Ed Taylor's Ventura shop one afternoon and picked a ripe 12.5:1 compression 355ci short-block for our test. Fitted with a strong Scat steel forging crank and I-beam rods rotating assembly with a set of SRP forged pistons, we opted for more compression to really put E85's octane rating to the test. Next we bolted on a set of Dart Platinum iron 215cc heads fitted with 2.05/1.60-inch valves. These are the latest wet-flow-technology heads available from Dart, and our flow data reveal the 215s to be a good choice for this test.

Since we wanted to push this small-block a little harder, we opted for a complete mechanical roller cam setup from Crane that pushes the valves open to 0.561 inch lift with 250/258 degrees of duration at 0.050 inch tappet lift. Combined with Crane's recommended valvesprings and set of titanium retainers, we also added a set of Crane Gold Race 1.6:1 rockers to ensure the valvetrain easily spins to 7,000. Moroso supplied the oil pan and pump that we filled with lightweight Royal Purple 5W-20. Since this was an rpm application, we went with an Edelbrock Super Victor single-plane topped with a Quick Fuel Technology 850-cfm annular discharge carburetor and an MSD billet distributor and 6AL ignition box. For the exhaust, we used a set of Hedman 171/48-inch headers hooked to a pair of 211/42-inch Flowmaster mufflers.

While the engine ultimately made 466 hp, our goal had little to do with ultimate power. (As it is, this engine made 1.3 hp/ci.) Of much more concern for this test was an engine that was both durable and repeatable and would allow us to evaluate the differences in fuel between race gas and E85. From that standpoint, this little 355 was a success.

Metering-Block Mania
At first, we thought all we had to do was plug bigger jets in a standard metering block to compensate for the less Btu output of our E85 fuel and we'd be in business. But after our test and in talking with the guys at Quick Fuel, there's more to this business than a quick jet change. They told us our test with the standard Quick Fuel metering blocks indicated it might be better to start with methanol-style metering blocks and then add the internal air bleeds that will help establish the proper fuel curve. This is because a standard Holley metering block maxes out in terms of fuel delivery with jets around 92 and a 0.070-inch power-valve channel restriction (PVCR). Increasing the jet size or PVCR beyond these points delivers a smaller percentage of fuel-flow increase. This is why drilling out the PVCR on our billet blocks didn't help all that much. It should have drowned the engine in fuel, but it was actually only worth a small percentage of additional fuel. The part number listed in the parts list is basically a methanol metering block configured with bleeds tuned for E85. This will guarantee sufficient fuel-flow capability to feed any normally aspirated engine.