Try this experiment...buy the same exact gaskets at NAPA and then go to advance Auto. Check the difference. You don't even need a Micrometer. NAPA is heavier and thicker. Unless there was a mistake in packaging at Advanced they are cheaper. And the thickness should effect performance to a certain level
Wow! That’s crazy. I’ll have to try that. And yeah, thicker gasket lowers the compression ratio a tad. I’d ordered my pair of felpros from Summit racing so that’ll be an interesting comparison