In the following months, the two railway companies ran comparative exchange trials between the two types from which the Great Western emerged triumphant with 4079 "Pendennis Castle". The LNER learned valuable lessons from the trials which resulted in a series of modifications carried out from 1926 on number 4477 "Gay Crusader". Changes to the valve gear included increased lap and longer travel, in accordance with Great Western practice; this allowed fuller exploitation of the expansive properties of steam and reduced back pressure from the exhaust, transforming performance and economy; the economies in coal and water consumption achieved were such that the 180 psi Pacifics could undertake long-distance non-stop runs that had previously been impossible. There followed a complete redesign of the valve gear, which was applied to 2555 "Centenary" in 1927, with the rest of the class being modified in due course. Locomotives with modified valve gear had a slightly raised running plate over the cylinders in order to give room for the longer combination lever necessary for the longer valve travel. Another modification was made in 1927 when number 4480 "Enterprise" was fitted with a boiler. This was closely followed by two other locomotives which also incorporated variations in the cylinder diameter and superheater size for comparative purposes. This led Gresley to make a radical departure from Churchward practice by increasing the number of large tubes containing superheating elements, hence increasing the superheater surface area in contact with the hot gases, thus raising steam temperature. The presence of the larger superheater could be recognised from the square covers on either side of the smokebox, a feature that the locomotives retained throughout the rest of their existence.