I use a differential pressure tester Model 2EM from Aircraft Tool Supply Company, see ATS PRO DIFFERENTIAL PRESSURE TESTER WITH MASTER ORIFICE from Aircraft Tool Supply
And I use accessory fittings for automotive spark plug holes and convenient hose reach.
Reminds me of my aircraft days Roger.
I have a similar problem with my S1 Sovereign. Starts ok , runs ok, but smokes when revved, Did a comp test and all low (sub 100) but no difference when oil squirted down bores. Suggests valves. But did leak down test and no issues anywhere, valves , rings, gasket. Mechanic who did test thinks it likely stuck rings as engine not previously run for some 5-6 years prior to my purchase, although he canāt explain why squirting oil didnāt improve the readings. His recommendation was to pour some " mechanic in a can" type product in the cylinders and drive the car gently to see if thereās any improvement. Maybe the same issue with yours, rings just stuck.
Good luck.
You need to differentiate between valves not sealing the combustion chamber and valve stems not sealing the oil from the intake and exhaust.
If oil runs down the valve stems you will have a little blueish smoke sometimes when you start it and often more when you drive off at first. Has nothing to do with compression readings.
Driving often helps in my limited experience. But if itās a lot I would be worried.
Iād suggest putting some miles on it under load, the rings need to seat.
Yeh, thatās the plan Dan. But it is a long way from being on the roadā¦maybe next year. Hopefully the rings will seat when it is driven.