Editing GWR 3700 Class (section)

==Modifications==
Superheating of the boiler was first applied to no. 3702, ''Halifax'' in June 1910. All of the class had been fitted with superheaters by 1912.<ref name=OSNb35>{{harvnb |Nock |1978 |p=35}}</ref> Boiler feed was originally by [[Check valve|clack valves]] fitted to the underside of the barrel.<ref name=OSNb37>{{harvnb |Nock |1978 |p=37}}</ref> [[Top feed]] was introduced in 1912 and new cast iron chimneys in 1921. The slide valves were replaced by {{convert|8|in|cm|1|abbr=on}} semi-plug piston valves from 1914.<ref name=OSNb35/> All the engines were fitted with steam reversing gear but only a few, including no. 3716 ''City of London'', had the gear replaced by the [[Reversing gear|screw reverse]]. The Dean suspension bogie was replaced by a bogie developed from the type used on the [[GWR 102 La France|de Glehn]] Atlantics.<ref name=OSNa81>{{harvnb |Nock |1977 |p=81}}</ref> Four retained the Dean bogies until withdrawal.{{cn|date=July 2023}}