How to rebuild automotive carburetors
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[[File:Holley transferslot.jpg]] <br style="clear:both"/> | [[File:Holley transferslot.jpg]] <br style="clear:both"/> | ||
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| + | ===Secondary vacuum chamber=== | ||
| + | On carbs that have a vacuum operated secondary, the secondary vacuum chamber is important. | ||
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| + | Use a fresh cork O-ring to seal the secondary vacuum chamber assembly to the carb body. Using a light smear of Hylomar on the cork gasket helps it to seal and stay pliable. A small rubber O-ring may be used instead of the cork gasket to seal a Holley secondary chamber. If you try this, be sure the O-ring is sealing, w/o being ''too'' thick. | ||
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| + | Be sure the vacuum chamber is assembled correctly. The diaphragm can get misplaced/torn; if that happens there will be no secondaries. Also, the check ball can get left out or can stick or the check ball seat can be rough, allowing the secondaries to activate too easily. So be sure the check ball is present and the seat is well formed. | ||
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| + | The seat can be re formed by using an old check ball and a small punch. Drop the check ball into the check ball passage, then with the vacuum chamber solidly supported, lightly tap the old check ball with the punch and a small hammer. This re forms the seat. | ||
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| + | '''NOTE:''' There are small groove(S) in the vacuum chamber check ball seat. This is normal, so do not try to use this method to remove the grooves. They need to be there to allow the secondaries to work correctly. | ||
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| + | A tuning trick is to use a deeper or shallower groove to change the opening rate. A tool can be made from a modified phillips head screwdriver to cut deeper and/or more grooves in the seat. Also, a lighter (aluminum) check ball can be used. | ||
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| + | To check the vacuum chamber, with the chamber off the carb push the diaphragm link arm back into the chamber, then use a finger to block the vacuum port that goes to the carb body. Release the link while keeping a finger over the port- it should remain retracted until you remove your finger from the vacuum port. Only when you remove your finger from the vacuum port should the link extend. This will let you know the diaphragm is sealing. | ||
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| + | If you use your lips or a vacuum pump to pull a vacuum on the chamber (chamber off the carb), there should be some resistance felt; the diaphragm shouldn't be too easily retracted because the check ball should be restricting the vacuum somewhat. That tells you the check ball is there and is able to help modulate the secondary opening rate. | ||
==Rochester Quadrajet carb== | ==Rochester Quadrajet carb== | ||
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