Note that whilst part number 503895 is in fact a bare casting, we supply under this part number 503895SH a second hand casting with all the valve parts in it.

Three types of oil filter head were fitted to TR2-4A. Many parts are not available now and some parts are not interchangeable, in particular the seal between the bowl (sump) and the filter head on a Purolator assembly is different to that found on a Tecalemit unit and if the wrong one is fitted, a severe oil leak could result. Fortunately replacement oil filters usually come with both seals!
TR2 and TR3 had what is known as a bypass filter head. This type did not have an internal blow off valve in addition to the pressure relief valve and operated on the principle that only a small amount of oil that was bypassed from the oil feed system was filtered. This was done to ensure the bearings were never starved of oil should the filter become blocked but did mean that dirty oil was inevitably fed to the bearings. This type of filter head is identified by only having one big hexagon nut visible on the head casting.
The TR3 to TR4 were fitted with a 'Full Flow' filter head by Purolator (Automotive) where all the oil is filtered. In the event that the filter becomes blocked there is an internal blow off valve that will allow oil to flow to the bearings. This type of filter head is identified by having one big hexagon nut visible on the head casting plus another sunken one.
TR4A's were fitted with the same Full Flow' filter head by Purolator or an alternative part by Tecalemit.
The relevant part numbers are as follows: -
301994 Complete assembly TR2-3 up to engine number 12649E; Bypass type
503895 Head only TR2-3 up to engine number 12649E; Bypass type
203271 Complete assembly TR3 from engine number 12650E to TR4A; Full flow type (both Purolator and Tecalemit parts use this number as the complete assembly is interchangeable)
505300 Head only TR3 from engine number 12650E; Full flow type Purolator
508770 Head only TR4A; Full flow type head Tecalemit

Please bear in mind that over the years, parts may have been swapped.
All other associated parts are accessible via the original part numbers on our website