An option for an adjustable air hole, (requires a drill press, a vice and some work but worth it if it is needed):
1. Find/buy a bolt of proper material type (may need a few incase you botch the first), with the same threads as the air hole but slightly longer than standard bolt while still able to fit under cap.
2. Spin on as many nuts as will fit on the bolt, lining up the outer sides of the hex pattern (like one long/fat nut, used for stability and mass when coring/drilling out the bolt).
3. Mount and center in vice (upside down) oriented so you can drill a hole into the bottom of the bolt.
4. (Air Manifold) Start with a small bit centered and go as deep as you can withour fear of punching all the way through. (Recomend using the adjustable depth stop prior to this step)
5. (Rechecking your stop depth) Increase in size drill bits and repeat until hole is as large as you are comfortable making it, the bigger the better but also presents more danger of punching through the side of the bolt if you are not accurately centered. (Remove nuts when complete, blow into new hole and make a whistling sound, pet the dog when he runs up).
6. (Vent Holes, 2 options)
a. With a dremel cutoff wheel, open a slot in the side of the bolt threads centered and staying away from the bottom end of the bolt. (For pro work, clean up thread with an approapriate die, correct file may be used also).
You may cut as many as 2 or 3 of these slits evenly aligned around the circumfrence of the bolt. See if 1 row fits the bill before jumping ahead.
b. Drill a series of small holes along the length of the bolt instead of a slit(s), 1, 2 or 3 rows evenly spaced. (if you want to get fancy and have better tuning ability, run holes in a spiral pattern down the bolt, (spiral oriented with the bolt threads) to progressively cover holes as you tighten bolt, bit between threads will provide stability when drilling).
NOTE: Later when complete and tested you can either trim off excess from bottom of bolt, or extend slit(s)/hole(s) pattern further to obtain more air and retest.
8. Clean up any burs and mount bolt in air hole. The deeper you screw it in the more holes are covered decreasing air flow.
9. If you find that you need to turn the bolt in too far (bottom is sitting down too far into tank), calculate and cut a length off of the bottom of the bolt (prior to tossing it and starting over) and determine if it is acceptable.
Rinse and repeat as necessary.
1. Find/buy a bolt of proper material type (may need a few incase you botch the first), with the same threads as the air hole but slightly longer than standard bolt while still able to fit under cap.
2. Spin on as many nuts as will fit on the bolt, lining up the outer sides of the hex pattern (like one long/fat nut, used for stability and mass when coring/drilling out the bolt).
3. Mount and center in vice (upside down) oriented so you can drill a hole into the bottom of the bolt.
4. (Air Manifold) Start with a small bit centered and go as deep as you can withour fear of punching all the way through. (Recomend using the adjustable depth stop prior to this step)
5. (Rechecking your stop depth) Increase in size drill bits and repeat until hole is as large as you are comfortable making it, the bigger the better but also presents more danger of punching through the side of the bolt if you are not accurately centered. (Remove nuts when complete, blow into new hole and make a whistling sound, pet the dog when he runs up).
6. (Vent Holes, 2 options)
a. With a dremel cutoff wheel, open a slot in the side of the bolt threads centered and staying away from the bottom end of the bolt. (For pro work, clean up thread with an approapriate die, correct file may be used also).
You may cut as many as 2 or 3 of these slits evenly aligned around the circumfrence of the bolt. See if 1 row fits the bill before jumping ahead.
b. Drill a series of small holes along the length of the bolt instead of a slit(s), 1, 2 or 3 rows evenly spaced. (if you want to get fancy and have better tuning ability, run holes in a spiral pattern down the bolt, (spiral oriented with the bolt threads) to progressively cover holes as you tighten bolt, bit between threads will provide stability when drilling).
NOTE: Later when complete and tested you can either trim off excess from bottom of bolt, or extend slit(s)/hole(s) pattern further to obtain more air and retest.
8. Clean up any burs and mount bolt in air hole. The deeper you screw it in the more holes are covered decreasing air flow.
9. If you find that you need to turn the bolt in too far (bottom is sitting down too far into tank), calculate and cut a length off of the bottom of the bolt (prior to tossing it and starting over) and determine if it is acceptable.
Rinse and repeat as necessary.
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