The MGA pushrod engine uses an external full-flow oil filter mounted on the right-hand side of the engine, alongside the dipstick, with its pipework also routed on the right. The filter removes metallic particles, combustion by-products, and contaminants from the oil before it is recirculated through the engine's bearings and galleries. On an engine that is now over sixty years old, maintaining the correct oil filter specification and changing it at the recommended intervals is essential to protect the internal components.
Tecalemit and Purolator Filter Assemblies
The MGA was fitted with two different oil filter assemblies during production: the earlier Tecalemit type and the later Purolator type. The change point falls at engine number 15GB26933, engines built up to 15GB26932 carry the early Tecalemit assembly, while engines from 15GB26933 onwards (including all 15GD, 16GA, and 16GC engines) carry the Purolator assembly or later Tecalemit variants with revised sealing arrangements. The two assemblies use different centre bolts, sealing rings, springs, and circlips, and the parts are not interchangeable between the two designs. Owners must identify which filter housing is fitted to their car before ordering replacement components, the housing castings carry maker's marks that allow identification, and the centre bolt thread is different between the two types.
Sealing rings between the filter head and the canister, and between the centre bolt and the canister, are specific to each filter type.
Filter Construction
The filter housing is a cylindrical canister that unbolts from the filter head for element replacement. A central bolt secures the canister to the head, with a sealing washer and spring maintaining the correct pressure on the element. The filter head is bolted to the engine block via a pipe adaptor, with banjo bolts and copper washers sealing the oil feed connection. The sealing rings between the filter head and block, and between the head and canister, must be renewed whenever the filter is opened to prevent oil leaks.
Filter Element Options
Replacement filter elements are available in two media types: a felt element (8G683) or a paper element (GFE102). Both are direct alternatives that fit the original filter housing. Paper elements offer finer filtration of small particles, while felt elements are the original specification on early production. Either type is suitable for road use with appropriate change intervals.
Oil Pressure Relief Valve
The oil pressure relief valve is housed in the engine block and controls the maximum oil pressure in the system. It consists of a spring-loaded plunger that opens at a preset pressure to divert excess oil back to the sump, protecting the system from over-pressure when the oil is cold and viscous. A weak or stuck relief valve will result in either low oil pressure (spring weak or plunger stuck open) or excessively high pressure (plunger stuck closed). The plunger, spring, cap, and packing piece are available individually, a packing piece can also be used as an alternative method of slightly increasing oil pressure on engines where the gauge reading has dropped due to general wear.
Spin-On Filter Conversion
A spin-on oil filter adaptor is available for owners who prefer the convenience of modern disposable filter cartridges over the original replaceable-element canister. The adaptor bolts to the original filter head mounting point and accepts a standard spin-on canister, simplifying filter changes and giving access to a wide range of modern filter brands. Right-hand drive cars require the narrower 75mm-diameter spin-on canister rather than the wider 96mm version, as clearance to the steering column is restricted on RHD installations. Once the conversion is fitted, the original Tecalemit or Purolator canister, centre bolt, spring, and sealing rings are no longer required.
Ordering Notes
When ordering oil filter components, the engine prefix (15GB, 15GD, 16GA, or 16GC) determines whether the early Tecalemit or the later Purolator/late Tecalemit parts are required. Engines up to 15GB26932 take the early Tecalemit components; engines from 15GB26933 onwards take the Purolator or late Tecalemit components. Filter elements are available in either felt or paper form, and a complete spin-on conversion kit is available for owners moving away from the original canister system.