This is another one of those crazy projects where I spent a lot of time and effort making something I could easily buy. What can I say? I just like making stuff! In this case, I modified some inexpensive air filters to precisely fit the SU carbs on Beck TD. These filters came from AutoZone, and were suggested by Larry, who's a member of the Volvo Powered MGs online group. He said that he had used them very successfully on other projects, and the price was right at around $23 per filter, including the lower housing and pretty chrome cover.
The first order of business was to modify the base. The filter base is designed to fit on a four-barrel carb. In the photo below, that neck has already been removed on the base on the left, and is still on the right one. You can see that there's a cast-in boss that has a hole for a screw that secures the base to the four-barrel.
It took me a minute to figure out how to hold it. What worked was to grip from the inside, and "loosen" the jaws to actually tighten them against the lip of the base. A parting tool was extended a couple of inches out of the holder to be able to reach, and the initial cuts were slow and light (0.002" at a time) to cut through that extra boss.
After that, an ordinary facing operation made sure the face was really flat.
With both bases prepped, I found a piece of 1/8" thick aluminum, and laid out a couple of back plates by punching a center point, and drawing a circle with a drafting compass. I later drilled that center to 5/16" for mounting on a mandrel in the lathe. But first, I cut the approximate circle shape using a bandsaw, and then sanded the edges to a pretty good circle on a belt sander.
On to the lathe, where I could really make the back plates round, and reduced the diameter to be a good fit behind the filter bases.
Careful measurement told me that the filter mounting holes in the SU carbs were 2.900 inches apart. That meant I could locate the center hole and then drill holes 1.45" either side. Note the small screw jack under the plate to stabilize it while drilling - there was one on each side, as well as the precisely sized parallels on the edges.
A quick stop by the carb ensured that it really fit. Now to let some air in...
I drilled the center to one inch, the largest drill bit I own. After that, I used a boring bar to enlarge the hole in steps. This is my first attempt at creating a GIF file for my blog - I hope the photo below is moving!
Another check, and the hole is just right!
Modern adhesives are so good - I had no problem gluing the parts together, using JB Weld to adhere the back plates to the bases. I neglected to take a photo, but I also slotted the bases to clear the mounting holes, and chamfered the holes for flat head screws sized 5/16-18. I had to modify the screws to reduce the head height, with the goal of a flat surface for the filter element to sit.
I let the JB Weld cure overnight, and then put it all together. The filters didn't include nuts but I found a couple of 1/4-20 knurled nuts I had previously made, and they worked fine. Looks great, and the car runs very well with the new filters installed. I might have to adjust the mixture slightly since the airflow is different, but so far it runs fine.
Here's the look with the bonnet closed. Perfect for Beck's retro-racer vibe!
Nice work and I'm happy to see the Logan at work
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