The air filter mounting bracket on a Kadron (Solex/Brosol/Empi) 40 carburetor is a bulky piece of hardware blocking the clean flow of air. This seems easy enough to remedy on your own. However, there are two companies that offer kits. Each claiming possible gains of up to 8 horsepower when using the stock 3.5”-element air filter. Sounds good.
Kaddie Shack’s “Hi-Flo” kit: Lifts the bracket by using long bolts with spacers that fit over them, plus other small parts. Cost is $29.95 for two carbs, plus $10.30 shipping (to NY), $40.25 total.
Low Bugget’s “Air Top” kit: Uses threaded rods that screw into the carb. You then drill two holes in the air filter’s top, and secure it with the included wing nuts. There’s also a cap to plug the original center hole. Price is only $13 for two carbs, but shipping adds $14.94, for a $27.94 total. Cheaper, but the drilled holes mean you can’t swivel or adjust the filter when it’s in a tight engine bay. Also, the kit should have locking washers so the rods don’t vibrate out.
My Way: Make the mounting studs from a 5mm x 0.8 threaded rod (mcmaster.com, etc.), which you then cut to fit. Or, buy four #10x32 4” machine screws (boltdepot, fastenere, etc.). Low Bugget uses #10 threads. I tried it and they seem surprisingly compatible with 5mm x 0.8. Plus the 4” machine screws are just the right length, so no need to cut.
The top is held up by either nylon locknuts, or spacers (old pushrods work perfectly). You then cut down the original mounting bracket’s threaded post to about 10mm. That’s it. Easy to do, and cheap.
Gaining up 8 hp?: Maybe on a high-performance engine. But probably not much improvement on a 1600. But still, it must help.