Mailbag: How to Get 440+ Horsepower from a Chevy 400

Got questions?

We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. Last week, we helped a reader make around 400 horsepower with their Chevrolet 400 small block engine. This week, we’ve decided to take the same question and turn things up a notch with ingredients to make 440-460 horsepower. Once again, the question was:

B.B. Hastings, NE

Q: I have a 400-cubic-inch small block Chevy. I would like to be able to get 400-plus horsepower from this engine while maintaining my car’s drivability on the street. The vehicle currently has a Powerglide transmission and 3.88:1 gearing. Do you have any suggestions for parts combinations that might help me achieve this goal?

A: Last week, we detailed how to make right around 400 horsepower, or just above 400 horses. This week, we’ll give you some tips on making power in the 440-460 horsepower range. First, since we’ve moving you well beyond the horse-per-cube threshold, you’ll need to step up to aftermarket cylinder heads. You can go with a set of cast iron and run around 9.5:1 compression ratio or opt for a set of aluminum castings and go with 9.5:1 to 10.5:1 compression. Either way, you’ll want to make sure your new heads have 190cc to 200cc intake runners. Other components that will help you achieve this power include:

• 1.5:1 ratio roller rockers
• 1 5/8-inch or 1 3/4-inch primary headers
• Single-plane, high-rise intake manifold
• 750, 770, or 800 cfm carburetor

As far as your camshaft, you’ll want something with .498- to .522-inch lift, 244- to 254-degree duration at .050-inch lift, and probably 110-degree lobe separation. This combination of parts should help your engine develop peak horsepower in the 5,700 to 6,000 rpm range and peak torque in the 4,550 to 4,900 rpm range. If you plan on taking your engine beyond the 6,000-rpm level, we’d recommend a mechanical/solid lifter camshaft.

Although this combination will yield some serious horsepower, it’s also going to make your vehicle less street-friendly and require you to swap out your 3-series gear for a 4.56:1 or 4.88:1 gear (with 25- to 27-inch diameter tires).