As the title says what is the smallest shim you guys would use without fear of catastrophic failure? I am helping a friend with a 450R he bought used; it became hard to start so we checked the valves. Both intakes zeroed out. We tear into it last night to see what shims we would need. It has 145’s in it now, according to my calculations it would take a 130 to get them close. Is this too close to risk it?