It's been a while but here goes......We're going back 30 years here but.. There is an angle under the flat face of the valve and it has to be perfect for the valve to seat properly when it is closed. Lapping is the smoothing and adjusting of that surface. Anyone please correct me if I am remembering wrong. Hey grump, where are you? You're needed here.
Jerry
2005 America, Green, Thunderbike exhaust
LEAD, FOLLOW, OR GET THE HE** OUT OF THE WAY!
| 
