Spin-off Oil Filter conversion 

At the time our cars were made, oil filters were relatively new and presented designers with problems. If they were to be as effective as they needed to be then there was a risk that, as they filled up with dirt, so it became more difficult for oil to flow through them. There was a risk that they would block and the engine would be damaged. 

The alternative was a By-pass system, where some of the oil was diverted from the engine to a filter and then back again. These could be much more effective in cleaning the engine oil but as it turned out, not till after damage had been done.  After a spate of rebuilds and conversions, R-R eventually settled on full-flow and almost certainly the best available at the time. 

Oil filters have improved considerably in the last 50 odd years. They cannot block because they have an internal by pass arrangement, they offer less flow resistance, filter out finer dirt and they have a one-way valve that stops the oil running back out of the system when the engine is not in use so the oil pressure comes up more quickly. If you add to all this fact that they are considerably cheaper and easier to change, it is, as they say a “No Brainer”, you need one for your car. 

Fortunately for us Flexolite of Malvern UK have Spin-off filter converters made for all full flow, post war sixes. These are beautifully made on a CNC machine, extremely easy to fit and relatively inexpensive.  As can be seen from the illustration, they comprise of an aluminium spacer about 1 ½” thick that fastens in the way the original filter did. The new filter fits below. The preferred filter is a Fram PH8A but there are plenty that can be used in an emergency.

Fitting a modern Air Filter 

All Post war sixes that currently use the wire mesh air filter may be interested in the Foam Filter that Flexolite has had designed and made for our cars. It is made by www.itgairfilters.com whose credentials are impeccable. The benefit to us is that the new filter works considerably better than the original and yet is still the same size and easy to fit. To do the same job with a paper element would be impossible because it would need to be a great deal larger and there is nowhere to put it. 

There is no doubt that even the S1 suffers with high wear rates on the top piston ring which is a sign of poor air filtration but can also be caused by short trips where the choke is never completely off, who knows? All we can say is that these engines cost a fortune to rebuild and that anything that can be done to prolong life has to be worthwhile. I have fitted them to my cars with no perceptible difference to mixture strength, performance or noise. They need to be cleaned and re-oiled regularly but are said to last 500,000 miles. By then we’ll all be pushing up daisies or an equivalent.

Flexolite can be contacted by phone 01684 541941 or by email: Derek@flexolite.co.uk

Flexolite Ltd. Brockhill Farm, Mathon Rd. Colwell, Herefordshire WR13 6EP