K&N Air Filters
The carburetors with a home made heat shield with a set of modified Cannon (I hate) headers behind.
The paper filters shown above have now been replaced by K&N units (July 2002). Photos to follow. The paper filters were used while shopping after the foam and chrome filters I had previously disintegrated from age.
I ordered the K&N Airfilters for the Spitfire twin 1.25 SU's, K&N Part number 56-1630, $46.51 each plus $10 shipping for total order from www.goairfilters.com
They have all other K&N filters and
stuff, but you need the K&N part numbers, the website is not well designed
to find things. I ordered the cleaner/oiler kit also. Part number 99-5000
$8.33 The filter units come pre-oiled
and do not need the kit in order to install and use the filters initially.
I checked a few other sites, this was the best price I found.
Use the K&N site for part numbers: www.knfilters.com
Here’s how I did the installation:
I bought (4) each:
1” stainless steel hex-head 5/16” coarse (18/inch) thread bolts,
locknuts for the bolts
lock washers for the above bolts
I have always been careful of the threaded holes in the SU carburetors in attaching the air filters. In attaching the backing plates to the carburetors for the K&N units I did the following:
I put the lock (spring) washers on the bolts and screwed the bolts thru the plate, gasket and into the threads in the carburetor. As the bolt started to protrude from the rear of the carburetor aluminum I held the lock nut there with a wrench and continued threading the bolt thru the carburetor and into the nut. As the bolt starts to compress the spring washer, I continued to tighten until the bolt was not quite tight. This means that the spring washer is not fully compressed. At this point I tighten the locknut on the backside of the carburetor until it is almost to the aluminum of the carburetor. The bolt protrudes about 1 thread thru the locknut. My theory is to not stress the threads in the carburetor by tightening the bolt into the threads of the carburetor. The spring washer keeps the air filter tight and the lock nut prevents the bolt from backing out and the air filter assembly rotating, thereby choking the carburetor, or falling off.