Whistling Holley 4160
Greetings:
I THINK I've done a full job of searching the archives for this "teaser". A very disturbing high pitched whistle which seems to come from the area of the air horn/throttle bores. It commences at idle and up to fairly high engine speeds where other intake air flow sounds may drown it out. It is NOT present on initial startup up when the choke is on and restricting air flow. But the whistle gradually begins to be heard as soon as the choke starts to open and is quite loud when the choke is fully open. I've had carburetors with worn throttle shafts before but none that ever whistled and you'd think that an intake leak would be more likely to whistle when the choke is on rather than off.
I've replaced the carb to intake gasket and all hoses and diaphragm checks made except the vacuum secondary. People I've talked with say that a vacuum leak is going to result in a very lean condition adveresly affecting driveability. But........such is not the case. And the plugs do not show a lean condition even after 100 plus miles driving (but then, at higher engine speeds perhaps the leak or escaping air is, in fact, not present?). I've also considered an air leak on the suction side of the pump introducing air into the bowls which is then escaping via the vents and causing the whistle. But I can't find a suction side leak and it doesn't run lean as you would expect with a suction leak.
Last fall I had to replace the power valve and this spring I rebuilt the original 4657 fuel pump. But I don't see either of those causing the problem. Tiny piece of dirt in one of the vents.....perhaps? But I've never heard a whistle like this. This is a model 4160 Holley on a '66 300 hp.....List 3367.
Any help?
Thanks.
Bill
I THINK I've done a full job of searching the archives for this "teaser". A very disturbing high pitched whistle which seems to come from the area of the air horn/throttle bores. It commences at idle and up to fairly high engine speeds where other intake air flow sounds may drown it out. It is NOT present on initial startup up when the choke is on and restricting air flow. But the whistle gradually begins to be heard as soon as the choke starts to open and is quite loud when the choke is fully open. I've had carburetors with worn throttle shafts before but none that ever whistled and you'd think that an intake leak would be more likely to whistle when the choke is on rather than off.
I've replaced the carb to intake gasket and all hoses and diaphragm checks made except the vacuum secondary. People I've talked with say that a vacuum leak is going to result in a very lean condition adveresly affecting driveability. But........such is not the case. And the plugs do not show a lean condition even after 100 plus miles driving (but then, at higher engine speeds perhaps the leak or escaping air is, in fact, not present?). I've also considered an air leak on the suction side of the pump introducing air into the bowls which is then escaping via the vents and causing the whistle. But I can't find a suction side leak and it doesn't run lean as you would expect with a suction leak.
Last fall I had to replace the power valve and this spring I rebuilt the original 4657 fuel pump. But I don't see either of those causing the problem. Tiny piece of dirt in one of the vents.....perhaps? But I've never heard a whistle like this. This is a model 4160 Holley on a '66 300 hp.....List 3367.
Any help?Thanks.
Bill
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