Singer Owner July 2000

The Oil Filter

Anon

Many people, not only Roadster owners, will experience difficulty in obtaining by-pass oil filters for their cars. The reason for this is simple - there aren't any more being made.
The construction of the by-pass filer is a little different from the modern full flow type because it does a different job. The by-pass type continuously bleeds off a small amount of pressurised oil, filters it and returns it to the sump. In a full flow situation, all the pumped oil goes through the filter and on to the working parts of the engine.

By-pass filters have a fine filter medium, and to maintain the oil pressure in the engine have an orifice to restrict the flow of oil through the filter. The orifice is on the filter outlet so that it does not get clogged up with dirty oil, and on AC filters is 0.059" bore or occasionally 0.046" bore.

Full flow filters have a more open type of element to give full flow with the minimum of pressure drop. They don't filter as fine, and of course have no restrictions. If one eventually has to be used in a by-pass application a restrictor must be fitted to prevent all the oil pressure from being 'syphoned' away. Anyone with low oil pressure should choose the smaller orifice size, or maybe experiment with a slightly smaller one.

So that is the basic information about filters. If a new one has to be plumbed up there are many ways in which it can a done, and Roadster owners may be interested in this method for 1074cc engines.

This design uses a paper element filter for cheapness rather than the tin can type. The filter unit is from the BMC Mini/1100 range, and rigidly mounted to the Singer block rather than over the starter motor. Mounted vertically it is clean and easy to change.

The sketch shows the plumbing. The two tappings into the block are different. The feed out to the filter/pressure gauge is 1/2" BSF, and the return is 1/4" BSP.