The Morris Ten Series M was introduced in 1938. It was a completely new car with unitary construction, although the styling was little-changed from the outgoing Series E. The engine was also new, being the 1140cc X-Series with an output of at 4600 rpm. Although an overhead valve engine like the M-Series engine fitted to the previous Ten Series E, the X-Series was a brand new design following the disappointing performance and reliability of M-Series, which was related to the older Morris sidevalve engines. The Series M's X-Series engine had a 'free-flow' eight-port cylinder head and adopted features from contemporary American engines including a pressurised pump-driven cooling system, a fully filtered lubrication system and an automatic tensioner for the camshaft chain. Along with the contemporary Vauxhall 10-4 the Series M was one of the first mass-market British cars to feature an OHV engine and the Morris was praised for the smoothness, efficiency and quiet-running of its engine. The car had a top speed of around . The running gear was otherwise very conventional, even old-fashioned, for the time, with solid axles with longitudinal leaf springs all-round. Plans had been drawn up to provide the unitary-construction Ten with independent front suspension and Rack and pinion steering, but these were shelved due to cost and marketing concerns, although the parts designed for the Series M would appear in the post-war MG Y-type saloon.