Never2Old wrote:
1, Are port edges supposed to have a sharp edge which would make it easy to measure or do they have a rounded edge so it's hard to determine the true dimension? This can change the measurement by a several thousandths, maybe tens of thousandths.
They should have radiused edges, especially where the rings need to slip past them without snagging. The radii do increase the duration to some extent. Some judgement is needed.
Quote:
2, Do I need a narrower caliper to measure port dimensions, one that will fit in the bore, or is there a different method to measure ports?
A caliper that will fit would be nice. A machinist's scale and some good glasses and a bright light will get you pretty close. I don't lose sleep over getting the dimensions to the nearest thousandth of an inch. I've held a scale along the bore and stuck a straight edge through the port so it hits the scale and read the intersecting point. A little mismatching of the three cylinders just widens the powerband slightly. Unless you're drag racing and trying to shave off another couple hundreths of a second, a wider powerband isn't a bad thing.