Walt, thankyou . I'm in the position you state other that in my assembly process I did seal the heads to cam carriers. To be honest that was a mistake and if I had thought this through properly I wouldn't have done it. This is the main reason why I don't want to strip it again. I know I could remove the heads and carriers as one but don't have confidence about re assembly giving me the super free turning cams that I achieved first time.
At 1.85 mm clearance i'm only 0.15 mm or 0.006 inch shy of the very safe clearance . I've seen lots of information that 1.5 mm is fine and even down to 0.8 so figure I'll be ok this time ...but a real lesson learn't. I'd never build a modded engine for a 911 but had done several standard engines so this has been a great experience/
I must say I was a bit surprised at the clearance problem given the lack of dimensional change on the parts and that the spec is well understood, Its just possible that my S cams are not original spec but they came from a very reputable source . Is there a simple way to check perhaps by measuring valve lift through the crank rotation and mapping it for inlet and exhaust at say every 5 degrees . I have a degree wheel and can easily set up a DTI on the valve retainer again maybe even on the cam lobe?
Here's a snap of the cam end marking ( I know its up side down)
and a home brew solution to snap ring installation ( not removal)
andy