the bore sizing tool uses the valves that are going to be used as set up.lock the 2 valves into the zeroing block,then take the bore gauge and zero to the size/diameter of the valve.now go measure the clearance.very easy to set up.

also,the clearance is put into the part,in this case the valve.11/32" intake vale usually measures ~.342" so in a 11/32" guide it would have ~.00175" clearance,same goes for the exhaust vale,they usually measure in at ~.341.so thats why you use the valves in question for checking the guide clearance.

What do you generally see out of the AFR heads? When we measured mine @.0018 we thought we would measure a Brodix BB3 to compare. Guide clearance in them was .0013-.0017

On the last set of 335's
Intake were.0011-.0014,honed them to.0015 and exhausts were.0014-.0016,opened them up to.0022.motors were 950hp 540's vortex have.

What do these videos tell me? that I know Zero and am glad Al K is local lol

Sutphen, out of curiosity, what is a good exhaust guide clearance on a mild, normally aspirated 600-ish HP engine? Do you need to go quite as large on the clearance? Not talking about extremely cold water temps like Full Force operates in - usually 75* and warmer where I boat.

That's exactly correct !!!!! I have one and also a pointed small bore gauge....

When mine were measured I was informed the sunnen was not good enough or accurate enough, now it's ok to use gimme a fukkin break.....

.0013-4" on intake and exhaust .0018-9" exhaust,i use good hi temp vitron seals and never see the guides oil the ports.

I've been using one forever and a day.