Whistling 750 DP

I have a whistle at around 900-1000 RPM, right about where the idle is set on the Dart. Anyone ever ran into this? It is pretty loud.

I am going to take a propane tank and move it around the carb to see if there are any vacuum leaks.

Also when tuning I adjust the idle mixture screws to get the best vacuum, however I could not kill the engine either going in or out. There didn't seem to be too much adjustment in them, but the car would run rougher, with less vacuum in both directions. Is it possibly I am into the primary circuit? Stock cam, initial timing at 18 degrees, vacuum advance on manifold vacuum adding 18-20 more degrees at idle/cruise.

In general, after the tuning yesterday the car is running *much* better. Before I would hit around 3K (not running it hard) and could hear the engine break up a little like too much advance.

You might try using a section of heater hose between the carb and your ear to locate where the whistle is coming from. Had a friend that complained he was getting a whistle coming from a carb I had rebuilt for him. Found the problem with three feet of heater hose. Turned out to be a sucked intake gasket. Same trick works for diagnosing water pump and alternator noises too.

I had that exact carb make a whistle like you described. It was a loose mounting/throttle plate, not seated flat on the manifold.

Sounds like there is a vacuum leak somewhere.

The thermoquad on my old junker truck whistles at idle speed, I finally figured that it is the primary throttle bushing (if it has any) on the left (linkage) side, raising the idle just slightly quiets it, so for now that is what I have done.

It also seems to have an internal leak, but it runs and starts like it is fuel injected, even cold, so thus far I have left it alone, but my mileage sucks, due to what must be , duh, the internal leak!

How much use has your carb seen?

Just a thought ...

Well, the carb was loose on the manifold, tightened it up and thought for sure that would have been it, but still whistles. I'll mess around with it more this week.

Any more ideas are welcome.

The carb has not seen much use. I picked it up a number of years ago. The guy I got it from had added jet extension (without a notched float...) and a 50cc pump. I removed the extensions and put a 30cc pump back in. Went through it, gaskets, etc. Otherwise it seems to work pretty well although still need to do some tuning as I am still get some breaking up 3-4k RPM running up RPMs through very light throttle, however could be vacuum advance adding to much or possible related to this whistling issue maybe if it is going lean. Carb has stock 70/80 jets right now.

Other thread here from yesterday, but now that I know where the timing is (18 initial/38 total) on the test drive tonight I stood on it and it pulled really hard and sounds incredible (first time I have really gotten into it hard since back on the road) last fall.