every time the engine stops if the gauge is higher than the connection to the block the oil drains back to the pan.i use an adapter fitting at the block 1/8 pipe to 3an then a 3an hose to a t fitting which is from an mgb which has an oil pressure sensor in it(in out sensor) for the light.then the copper line from t to gauge all from an mgb readily available from the usual suspects.pressure per rpm is the important reading not is 50psi or 45psi the correct reading.you could use a 3an hose from block fitting to gauge fitting if desirable.