I got a buddy with a T/A clone. The Six Pack has recently developed a whistle that we have been unable to diagnose and repair.

The whistle occurs at all engine speeds. Seems to be coming from the center or rear carb. It's actually more of a whine than a whistle.

We have not found a vacuum leak. I have vented a propane torch around the carbs, but I get no reaction unless I shoot it straight down the throat.

Car does seem to be idling a little lean, which supports the threory of a vacuum leak.

We have removed the center carb and replaced the base, and base to body gaskets, and replaced the base gasket on the rear.

I've also disconnected the linkage to the rear and throttled it manually to see if I could isolate the problem. It didn't.

Next step is to replace the base to body gasket on the rear, but with no positive diagnosis of a vacuum leak, I have my doubts this will resolve the issue.

The carbs are relatively new, and in good shape. Visual inspection reveals nothing out of whack.

This should be a relatively simple problem, but thus far it has me stumped.

Beyond replacing the rear carb gasket, next step will be to block off that carb, or swap it with another. He's fortunate enough to have two six pack cars in his garage, so we can do some swapping if it gets to that point.

Anybody have any other ideas?