Gen III V-8 Cylinder Head Shootout
Here's a secret: If you want the best heads for performance, make sure your heads have these small triangle marks below every spark plug hole. The marks are left by "chills" used during the casting process in GM's semi-permanent mold (SPM) tooling. Of the three casting facilities that make Gen III cylinder heads, two use SPM tooling, the other heads are sand-cast. The SPM tools produce heads with very smooth, consistent ports and chambers which consistently dyno at least 4 to 7 hp better than the sand-cast heads. View Related Article
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