Q&A / Tech

Monday Mailbag: The Importance of Matching Camshaft and Cylinder Head Size

 

You’ve got questions. We’ve got answers — Mondays, when the Summit Racing tech department tackles your automotive-related conundrums. This week in our Monday Mailbag we’re looking at the relationship between a bigger cam and your cylinder head size.

Q: I own a 1986 Camaro. I recently installed a 1969 327 and a Turbo 400 transmission. The engine has cast pistons, a Weiand Stealth intake manifold, a 278/288-degree camshaft, and the heads off the car’s old 305.

The engine is strong, but I would like to get more power out of it. I want to use a 292-degree duration cam, but would that work with the 305 heads, or would I need a set of aftermarket heads? What heads would you suggest?

A: You’re going to have to go with aftermarket heads if you want to use the bigger cam. The 305 heads would require $800-$1,000 in custom work to get them to flow well above 4,000 rpm on your 327. The heads you select should have 64cc or smaller combustion chambers. Anything larger will drop your compression ratio too low. We’d go with a set of aluminum heads if you can afford them. They are about 40 pounds lighter-per-pair than cast iron, and aluminum dissipates heat better than iron. That means detonation is less of a problem.

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