Valve job ?

How much power are you leaving on the table by not having a performance valve job? Whether it's a BBF or SBF or what ever engine you are running. I'm just wondering.

those whatever engines, you can change the oem v/j specs and lose

Depends on the heads, you can kill it or see drastic improvements. I've see 40 cfm on well ported heads with the correct valve job vs the wrong one.

Also keep in mind their is more to a valve job than a seat grind.