We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re helping to choose the proper carburetor for a 400-cubic-inch small block.

D.N. Bedford, OH

Q: I’m building a a Chevy 400 small block for my 1986 Camaro. I’ve got a set of ported and polished heads, and I believe they have 55cc combustion chambers. I plan on running .030-inch over flat-top pistons at a 9.5:1 compression ratio, a COMP Cams Xtreme Energy cam, and an Edelbrock Performer 1,500-6,000 rpm intake manifold. Can you recommend a carburetor for my small block?

A: It sounds like you’ll have a strong runner on your hands when you’re finished. There are a couple of major considerations when matching up a carburetor to your engine and vehicle application: cfm and secondary. Holley’s 670 cfm Street Avenger carburetor is recommended for engines producing 300-400 horsepower and is a great choice for serious street performance and track duty, too. This carburetor also features vacuum secondaries, which is the ideal setup for producing low-end torque for the street and some weekend track action.

You can confirm your combustion chamber size by using a cylinder head cc kit and then enter that information into this compression calculator to dial in the piston profile to achieve your desired compression ratio. Also, you should make sure the steam holes in the cylinder heads have been drilled out so your engine doesn’t overheat.

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