Land Rover Serie II, IIA und III (1958-85)
The bellows thermostat used in the 2.25 engine is no longer available. Just replacing one with a conventional type thermostat will not do the trick because much of the coolant will bypass the radiator.
The bypass circuit allows coolant to be circulated within the engine before the thermostat opens and prevents hot spots in the head that can cause cracking. So you can not just block it off.
There are two alternatives: One is to replace your old thermostat and bypass housings with the newer Land Rover versions that have a built in restriction.
The other method is to make your own restrictor gasket that blocks off the bypass housing except for a single 3/8 inch dia. hole: then use a thermostat that will ﬁt your existing housing.
If you make your own bypass restrictor gasket, the correct thermostat to use is 74° C (order no. 342458) or 84° C (order no. 357729).