mock it up without the springs or you can use a "checking spring" which is a super light spring that just barely puts tension on the retainer and holds up the valve enough so you can still easily depress the valve tip with your finger. You can measure the distance between valve spring seat and bottom of retainer with a telescoping gauge, or even an inside hand-caliper and then measure those in a micrometer, or in a pinch a dial caliper. You can compress the valve spring in a vise to the now measured installed height, then crank it in until you reach the full lift compressed height and check for coil bind clearance. Next you can depress the valve the specifield lift amount and measure the clearance to the guide and seal with feeler gauges stacked to fit the gap. There are other ways to do it. Be creative, but thorough. Even if it's probably