Three distinct oil filtration systems were used across the 1275cc range, and the 1500 uses its own separate arrangement. The filter type is determined by the engine serial number prefix, ordering the wrong filter or filter head will result in components that physically will not fit. The engine number should always be confirmed before ordering oil filter components.
Bowl-Type Paper Element Filter
The earliest 12CC engines and early 12CE units (up to engine number 12CE/Da/H10308) used the original bowl-type paper element filter. This consists of a canister-shaped filter head bolted to the block, a removable bowl secured by a centre bolt, and a replaceable paper element that sits inside the bowl. The bowl must be carefully reassembled with the seals correctly seated, the pressure plate, sealing ring, and spring washer must be in the correct order, or the bowl will leak oil under pressure. The centre bolt seal should be renewed at every filter change.
Spin-On Filter Systems
From engine number 12CE/Da/H10309 through to 12V778392, a spin-on canister filter was adopted with a revised filter head. The spin-on arrangement is vastly simpler to service, the old filter unscrews and the new one screws on, with no loose parts or seals to manage. The filter head bolts to the block with a pipe connecting the head to the oil gallery. A third change, at engine number 12V778F393, introduced a different filter head and adaptor while retaining the spin-on format.
The filter head gasket should be renewed whenever the head is removed from the block.
1500cc Oil Filter
The 1500 uses its own filter adaptor bolted directly to the block, with a spin-on filter specific to the Triumph engine. An oil stat, a thermostatically controlled bypass valve, screws into the filter head and ensures that cold, thick oil bypasses the filter element until it reaches operating temperature, preventing the excessive oil pressure that a cold filter restriction can cause. The 1500 filter, adaptor, and oil stat are all specific to the Triumph engine and are not shared with the 1275cc.
Spin-On Conversion Kit
A spin-on conversion kit is available for early 1275cc engines still fitted with the bowl-type assembly. The kit replaces the entire filter head and bowl with a modern spin-on adaptor, providing the ease of servicing offered by spin-on filters with the wide availability of standard filter elements. The conversion bolts to the original mounting points on the block and requires no modification.
This is a popular and practical upgrade for cars in regular use, where the simplicity of spin-on filter changes at every oil service is a genuine time-saver.