Q&A / Tech

Monday Mailbag: Converting a Race Engine to Pump Gas

 

Got questions?

We’ve got the answers—Mondays when the Summit Racing tech department tackles your automotive-related conundrums. This week, we help convert a race engine into a pump gas street motor.

R.F. • Morgan, GA
Q: I plan to install the stroker motor from my former race car into my recently purchased 1970 Camaro (after I repair the body and give it a fresh coat of paint). The engine is a 4-bolt main, GM 350 that’s bored .060 inches over and makes 11:1 compression. It has World Sportsman II iron heads, forged pistons, a .633-inch/.633-inch intake/exhaust roller cam, MSD-6AL ignition box, and a Holley 850 cfm double-pumper carb. The Camaro has a Turbo 350 transmission with a shift kit and a 3,500 rpm stall converter driving a 10-bolt posi rear end and 3.73 gears.

The car won’t be a daily driver, but I plan on driving it on weekends and to the occasional cruise-in as well. I’d like to replace the carb with something that’ll give me good performance along with better mileage—what would you suggest? Also, I used to run 110 octane when I raced, how much timing detuning would you recommend for street use and would it be possible to run 93 octane gas in this combo.

A: It sounds like you’ve built an awesome race engine, but you’ve got too much cam and compression to run 93 octane gas. Plus, your 3.73 gear will cause your 3,500 rpm stall converter to slip under normal street conditions and hurt your mileage more than your big carburetor. To improve your mileage, lower your cam, compression (to 9.5:1 or less), and stall speed (to 2,500 rpm) and then you can use a smaller carburetor and pump gas.

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