|The Europa Side - Twin Cam Air Cleaner|
By Randy Tragni
Having been to many of the GGLC autocross' I can attest to the fact that a whole bunch of the Europa's out there are running around without an air cleaner installed to the GRP carburetor "plenum" box or in some cases no plenum period! Not at all a good idea. To start with the air cleaner is there to keep the vcuum created by the engine from sucking in small animals and rocks and such. This equates to dirt and grit getting sucked into the cylinders and scrapped around by the rings. The end result wil be premature wear and failure of the engine. The plenum is there to increase the length of the intake, thus tuning the system for some specific set of performance characteristics. We can assume that Lotus knew what they were doing in this aspect of design.
As I wrote in an earlier article I've recently converted my engine back to the Stromberg head. This has forced me to learn to live with the stock carbs and their numerous short comings. Upon initial installation I came to the immediate conclusion that the stock air cleaner, though properly designed and fully functional, is too big and bulky. It also makes it a chore when it's necessary to remove the rear trunk.
A few quick measurements indicated that the opening to the plenum was through a 3½ inch diameter hole, so with tape measure in hand, it was off to K-Mart. Now why would anyone go to K-Mart to look for an air cleaner? Because they have a large selection of air filters on the shelves that you can look through and they are down right cheap! Excuse me, inexpensive is the proper definition.
I found a Motorvator MPA-86, which is made by Purolator, for less than $3. (AC #A633C which fits 84-87 Buick Regal V6-231 or Cadillac Allante, plus a whole bunch of other GM cars). It is a snug fit over the end of the plenum. It also has about 3 times the surface area of the stock air cleaner element, which should improve top end breathing.
To mount the element up to the plenum requires some preparation. First, try to slip the filter over the end of the plenum. If this works you got the right part. If not somebody probably switched the boxes around. Take it back and start over. The element is a cylinder that is open to both ends so one end needs to be capped to air flow. This is really easy! Trace the outside diameter of the filter on some stiff material and cut it out with an old pair of scissors. I used 0.030 aluminum, but non-corrugated cardboard should work just as well. Use silicone adhesive to glue the cap onto one end of the element. Put a weight on top of it and let it dry overnight. You might want to crefully paint the cap for cosmetic reasons.
After the filter assembly is dry you are ready to glue the element onto the plenum. Apply a medium layer of silicone approximately 1/2 inch back from the outside edge of the plenum around the opening. Slip the filter on turning the assembly while you push to help spread out the silicone. Push the filter in about 1 inch. Straighten it up and you're done. Let it dry before you drive.
When the time comes to change the filter it will be necessary to cut the old filter and pry it loose. Then carefully scrap the old adhesive off before you start over as above. This is a whole lot easier than it might sound.
This modification worked out well for me, but you do this at your own risk. And yes, this modification allows the trunk to be removed without having to disconnect the air cleaner.
As in every thing you do to your car in California, no guarantee that this is legal!