68 440 factory carb. lean issues

[no318]

I recently finished my 68 Charger RT 440/auto.  It is a #'s car with the original carb. on it.  I rebuilt the engine and other than a very mild cam, slight stall convertor and mopar elec. ignition, it is stock.  My problem is that it has a lean bog when accelerating under light to moderate throttle and surges (like it is lean) at 45-60 mph.  If I stand on it, it runs good.  There is no problem when the secondaries are open.

I took the top back off of it the other day and found that the left side float bowl fuel level seemed noticeably lower than the right.  Even though the float is set slightly higher on the left side.  I blew through all the passages (I think) with carb spray and saw no restrictions.  It runs fine under higher load/rpm/secondaries open, so I can't see how fuel level in the float could be the cause.

Any advice?   I am about tempted to install a 750 performer carb. that I have to test drive it and see, but I really wanted to use this original carb. on it.

Thanks in advance.

[TylerCharger69]

I'm wondering.....could there be a pinhole in one of those floats causing more fuel to enter the bowl than normal??   I had an old carb that had that issue.

[375instroke]

Do you have this hole?  Try plugging it and see if it gets better.

[John_Kunkel]

When you remove the primary booster you'll find two brass tubes, one is larger than the other, the smaller tube will be necked down at the bottom. Using miniature drills, find the size the opening in the smaller tube and increase it a couple of sizes. This will usually eliminate the "tip in" stumble and lean surging at light throttle.