I never actually measured it but when you have steep ugly chambers like small block Mopars has it allows you to shape it a little bit. (Pictures of 4.120 mark. 4.180 felpro gasket) that we all ran for years. I only wish I had my heads off my engine to take a 30 second look at them. When I ported them in 2008 I’m about 99% sure I opened the chambers to 4.180 because I ran that gasket on three or four different engines. Those heads flowed 318cfm with the help of my Super Victor intake. Now for three years I’ve ran a 4.060 Cometic head gasket and didn’t burn it out. So am I worried about something for nothing. Hmmmmm time will tell when hopefully I pull them and put a better set on
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