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Message: <blockquote data-quote="Addicted" data-source="post: 1463389" data-attributes="member: 24638">It is official! I took great measurements today and found that a bone stock NPI head has .560" lift is the exact amount of room it takes for the valve retainer to physically touch the top of the valve seal. The valve keeper sits up into the retainer around .040", so when retainers touch the seal, the keeper still has room. If they both set flush together I could run my camshaft without any worry.  With the valve seal removed, I measured from the bottom of the spring pocket to the top of the valve guide, it measures .600". I measured the whole valve seal from top to bottom, it came to .805". The valve seal base is .040" thick, and the valve spring sits down on the seal base.      The space between the seal and guide on the inside is over .100", so if we could get a shorter valve seal height, we would be able to run a higher lift in the NPI head, and not have to worry about anything except coil bind.   There's another way everyone can run a higher lift cam, change seat pressure, and change valve spring install height all at the same time. With that we could run the same valve seal as we do now with no modification to it. I will get into that in another post.  Just to sum things up my .556" lift cam is to close for comfort, and needs more clearance from retainer to seal. I would feel safe with .020"-.030" clearance, so let's get it there.<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" /></blockquote>