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· SAE Member; ASE, AERA cert.
399 Posts
Pro Stock engines (GM) generally use symmetrical port heads such as Dart Big Chief. The teams generally massage the heads to a great deal, but the original combustion chamber volume of the Dart symmetrical port head is about 80cc. Flat top pistons are used with very low valve angles (about 12 to 14 degrees). This way there is not a piston dome sticking up there, restricting flow especially on the intake side.
Pro Stock headers are available from Hooker, Hedman and others for these engines in tube-frame cars. Most of the teams modify these headers and/or build their own. Primary tubes are usually 2.250" to 2.375" diameter and very short, but adjustable in length. Collectors are generally 4 inch diameter or larger.

The intake system, heads and headers are specifically designed as a combination for these cars. Bore is very large (about 4.750") with short stroke (3.000" to 3.500") and very long rods. This design combination allows these engines (NHRA 500 cu. in.) to make power all the way to 9000 RPM.
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