On 3/1/2020, Michael Anderson in Australia wrote:
"You previously asked to supply photos from a Twin Cam owner who fitted a crankcase ventilation system air inlet by drilling into the inlet camshaft cover and passing a hose to the rear SU air filter. We have had no volunteers agreeing to drill into rare Twin Cam parts. Instead we are all going to fit a filter to the oil filler opening. I have loaded a procedure to the IO website".

On 2/19/2020, Michael Anderson in Australia wrote:
"The main difficulty is sourcing an adapter with a British Standard Pipe (BSP) thread of 11 threads per inch (TPI) and a parallel thread (BSPP). Most plugs are tapered (BSPT). A company in the UK has the correct item. The company is called Essentra and their part number is 498686. (Note: For some strange reason Hydraulic component companies list plugs with a 1.75" diameter as 1.5"). Essentra (USA) mainly stock plugs with a UNF thread and Essentra (Australia) mainly have Metric threads.

"The filter to use is the K&N part number 62-1015. This filter is 51mm (2") in diameter, 38mm (1.5") high excluding the tube, and the diameter of the tube is 13mm (0.5"). This filter has a chromed top which nicely matches the Twin Cam engine. Many K&N filters have a rubber top.

"The fitting procedure is shown in the attached photos. The filter should be glued to the adapter with a temperature resistant adhesive".


Drill 1/2-inch hole through center. Slice off the top hex part flush with the flat top surface. Glue the intake air filter to the adapter fitting.

Here is another one (below) done by Andy Hinton in the UK, The center hole was drilled, but the extended hex boss was not removed. That makes it a bit taller with a small space below the filter shell. Andy reports that his filter fits well into the drilled hole and does not need to be glued in place. If you do want to glue these parts together, JB Weld works well. Not to worry about temperature resistance of the adhesive, as the plastic will suffer from heat long before it gets hot enough to bother the JB Weld.

The plastic pipe plug may be available in black. You could otherwise paint the plastic bit dark red.

At 08:25 PM 3/4/2020, Ian Prior wrote:
"Another alternative would be to use a Brass plug available from Reece Plumbing supplies here in Melbourne and throughout Victoria. Product code 209135 - Plug Hex Square Brass 40mm" - [actually octagonal, very appropriate for an MG].

Yes BSP, 11-TPI. It does screw all the way down, but the thread will need cutting back ... to clear the chain... . About 1/3 needs to be docked.
Being brass, it may be recoverable next time you need to change the filter. With the narrow flange, the original copper seal washer will likely not work, so use an O-ring.