I give up , I can't seem to get the fuel line to the fuel bowls from leaking. It's a hard tube , dual feed chromed line ( Holley ) going into a new Holley DP. There's no chrome on the leading threads and I've tried teflon tape ( couple threads back from the lead ) I'm afraid to overtighten, as it sems that may not help. The leak isn't just a trickle eitjer, seems like something is not right??

take the fuel line and carb fittings off and look at sealing surface (flair at end of tube) to make sure there are not nick or flaws in sealing surface

look at those fittings real close... almost sounds like you have a pipe thread fitting in the carb. Do they both leak? the flare fitting on the fuel line would screw into pipe thread, but would not seal. Is there a matching flare seat in the carb fittings?

My 700 DP seals with a thin metal 'o-ring' at the carb fuel inlets. This is with a Russel dual feed line. What does your feed line ends look like?

OK spent a few more hours messing with this ( and watching Bristol, man what a track!) I took the fitting off the carb and took a REAL good look at it with an eye loop. Looks good , no nicks scratches etc. The previous fuel line I had on was also a chromed hard line, but that was steel and had a barb end on it and I was converting over to braided line and threaded fittings. Didn't have a problem with that one. The old and new lines are both the standard double flared ends, which is what I assume makes the seal, not the threads on the fitting. The threads on the rigid fuel line are just class 2 UNC of UNF threads.. The primary side leaks far worse than than secondary , in fact i'm not sure if the secondaries leaked at all the last time around.
I would think that since the hard line I'm trying to make work is made of copper it would conform nicely to the seat on the fuel inlet fitting when I snug up the fitting. Maybe there's some irregularity on the surface of the flare I just don't see.
I'm going to return this one and try another, can't hurt.

Make sure the gasket that goes behind the flare adapter (the big nut that screws into the bowl) is centered. Sometimes the gasket ID is a bit larger than the fitting OD and the gasket shifts and leaks. If the gaskets are good and centered than try cranking a little more on the flared fittings (the smaller ones). Sometimes the cheap ones don't seal very good unless you crank 'em down.

Teflon tape is for water pipes. No sealant is needed for flared fuel lines.

Yellow teflon tape is ok for gasoline fittings.