Q&A

Mailbag: Race Fuel vs. Pump Gas

Got questions?

            We’ve got the answers—Mondays when the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re answering your questions on race fuel and ring and pinions.

 

From: Robert Tuck • Stockton, CA
Q: I am in the process of building a circle track vehicle. I purchased a Chevy 383 four-bolt main and equipped it with a Dart Iron Eagle top-end kit (DRT-01110002) and an Eagle Street and Strip rotating assembly (ESP-B13005E030). With a compression ratio of around 10.9:1, can I run on pump gas or do I need racing fuel?

A: There are some simple guidelines to stick to when it comes to choosing the right fuel for your racer. If you’re running iron heads, then anything above a 9.8:1 compression ratio will require more than pump gas. On the flip side, aluminum heads can support up to a 10.5:1 ratio on pump gas. Since your engine is equipped with iron heads and has a 10:9:1 compression ratio, you’ll need to run race fuel.

 

From: Don Blackwell • McAlester, OK
Q: I am turning my 1964 Chevy Malibu into a drag car. I am running a 1974 Chevy 454 with an Edelbrock Air-Gap intake, a single four-barrel carburetor, a mid 1970s Powerglide transmission, and a Ford 9-inch rear end. It also has a four-link suspension with coil-over shocks. I was wondering what type of gears I should install in order to run 1/4- and 1/8-mile races? I have a nickel and dime pocketbook. Can you help?

A: Since you’re well on your way to building a race-winning drag car, you’ll want a set of gears that will plant every bit of power to the pavement and still be pulling at the end of the run. Your best bet is with a 4.86- or 5.14-ratio ring and pinion gear set from Richmond Gear (RMG-6900671 or RMG-6900681). They’re specifically designed to withstand the rigors of racing. Plus, they’re affordable so your pocketbook will approve.

After gaining some serious pulling power, be sure to look into a good set of drag slicks. All that power is no good if you don’t have rock-solid traction!

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2 Comments

  1. So then why does a bone-stock LS3 run fine on pump gas (even 91 octane) at 10.7:1? Accuracy of the fuel injection system? Better cooling? Something else?

    Just seems odd that 10.5:1 is so often quoted on this site as being the upper limit for pump gas, when factory engines are going beyond. I think a deep dive into your reasoning behind this statement is in order.

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