340 cam for 318

The listing says it’s a 4.14” gasket bore diameter. Is that accurate?
Yeah. It's correct. The Cometic I posted has a 4.040" gasket bore. This is why I always use compressed volume and not compressed thickness if I want to gain a little compression. The difference between the 318 bore and that Mr Gasket part number is .230". Almost a 1/4". The Cometic is .130" larger. That's why I posted the Cometic. He's gonna need all the help he can get. If I'm going for quench, then I pay attention to compressed thickness.