Q&A / Tech

Mailbag: The 9 Things You Should Know Before Ordering a Camshaft

You’ve got questions. We’ve got answers—the Summit Racing tech department tackles your automotive-related conundrums. This week in our Mailbag, we’re discussing what you need to know when choosing a new camshaft.

Q: I bought a rebuild kit for my stroker 383 Chevy. It’s .060-inch over (388 cubic inches) with TRW flat top pistons, 10:1 compression, and Brodix Track I heads with 69cc combustion chambers. Now I want to increase my compression with a set of Speed-Pro L2252AF pistons. With 64cc, I will have 13.5:1 compression. But with my 69cc heads, the compression will be less.

My big question is, what camshaft should I run with my latest combination? Please consider something so the valves won’t hit the pistons. The engine will be racing only.

A: We’ve love to help you choose a cam, but we’ll need a more information about your engine and vehicle. Whenever you order a camshaft, you should be ready to supply the following information:

  • Engine type and cubic inches
  • Engine compression ratio
  • Type of cylinder heads
  • Induction system (carbureted or fuel-injected)
  • Vehicle weight
  • Rear-end gear ratio
  • Rear tire height
  • Torque converter stall speed if you have an automatic transmission
  • Intended application (street, drag racing, oval track, etc.)

You are right to be concerned about piston-to-valve clearance when choosing a camshaft. While you can pick a cam with mild lift and duration specs to be safe, that doesn’t always work when it comes to radical race cams and dome pistons. The only sure way to determine proper piston-to-valve clearance is on an assembled engine. A general rule of thumb for clearance is .080 inches on the intake side and .100 inches on the exhaust side. Check out our earlier video for more on checking piston-to-valve clearance. If you find you need more clearance, you’ll have to flycut the pistons.

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2 Comments

  1. Ed Pelaggi says:

    You never mentioned LSA which means a lot.

  2. Johnny Williams says:

    What about stroke rod ratio? That determines piston speed and and swell time at top and bottom dead center. Yes sir pick a cam without more data. Might make a decent no on the Dyno, but rev time could be like a DUMP TRUCK.

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