How important is it to retorque cylinder base nuts and readjust the valves on a radial engine?
A. Readjusting valves is very important. After an overhaul as the valves seat in, the adjustment will change (usually the valve tightens). If the valve lash reaches “0”, then the valve will be held open all the time, with a resultant loss in compression and eventually a burned valve. We recommend readjusting the valves at the first 25 hours after overhaul (we adjust them before and after the test run) and every one hundred hours thereafter. Retorquing cylinder base nuts is an important operation that is often overlooked. See “Maintaining the Jacobs Engine – Retorquing nuts”. This article speaks specifically to the Jacobs engine, but this information is generally applicable to the Lycoming and Continental radials as well.
