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Figured I would bounce this around for the experts:
I have a vacuum leak when the 230 flat head six warms up. There is a constant high pitched whistling (sucking sound) near the front of the engine (carb side). I have used the usual starting fluid to try to find this leak, no luck with increased rpm. The carb was rebuilt and mating surfaces planed on a lapping plate until flat. Lots of time to get them flat. I know these carbs, the ETW1 are famous for warping and having vacuum leaks. The carb is not the issue. If a lifter side cover or the fuel pump gasket are at fault, this would lead to a constant whistling vacuum leak? Also, if there is a crack in the front tube of the intake manifold I would have this also. The vehicle's engine is worn. Cylinders run 95-100 psi on compression test. Also, the vacuum measured at the intake manifold plug when idling is about 14" of vacuum. Reading this forum, guys with the 251 flat head six experience 18"-22" vacuum, engine in good condition. I figured a 230 flat head six should be about 16"-20"?
Has anyone experienced a vacuum leak on a side cover or fuel pump with whistling? With the PVC sucking additional crankcase air into the carb intake due to a side cover leak, it would lead to a lean fuel mixture and poor running engine & dying under load. Your thoughts?

wiper hose leak?

NV

A 230 will pull 18-22" if it's running OK. If your idle screw is out more than about 1.5 turns you've got yourself a leak.

If the leak is loud enough to hear you may try narrowing your search by using a length of flexible tube and listening to the end of it while fishing for the leak. Check all of your PCV fittings, I've had one crack and it took some searching to find it.

Good luck,

Andy

What Nam Vet said. There is a vacuum line running from your fuel/vacuum booster pump to the rear intake port. It runs through exactly where you say you hear the vacuum leak. above the manifold next to the head.

-jim lee