Fuel Line Routing or Something Else?

[Sparky51]

Just rebuilt carbs. (New LS jets and float valves,) new gaskets all around, rebuilt petcock, all new vacuum lines. New intake manifold gaskets, as well as vacuum port plugs.   Petcock fully tested with vacuum for  proper flow.   Did a great synch job with the Digi Sync.

Almost good!  No longer am I  backfiring, popping. Nice smooth idle too.  Problem now is when in higher RPM, and "Getting on it" she is missing like she is running out of gas.
Checked so far: Vent line not kinked.  Coil 1/2 primary wiring is right and tight, (had to remove to get carbs out.) No loose clamps on the rubber hose clamps,(18) and even tested with carb cleaner for a leak at all connections at the tubes and vacuum ports.

No Kink in the fuel line, however after removing the tank  the gas lines that go right and left from the main "T"  are not exactly the same. The right side line goes slightly up hill to mate up with the T on the fuel rail. The left side is all down hill, below the Pair Valve hoses, to the fuel rail.  Could a slight "hill" in the right side cause it to not flow fuel properly?

The only other thing that comes to mind is that the petcock line is that Red Eye line, and I had forgotten to slide the finger clamp up and over the nipple at the petcock. (discovered when I removed the tank afterwards to check for kinks, and coil wiring)   However I have a hard time believing that I could have enough of a drop in vacuumm there that would not let the petcock go to full open.   

Any ideas?

Thanks

[BonS]

Have you thoroughly, and I mean thoroughly checked the rubber airbox boots to be sure that they're down all the way onto the carburetors? These fittings have a great tendency to hang up on the back side of the carburetors where you need a dental mirror and flashlight to detect the problem. Any air leakage there will make that particular cylinder run fat at high rpm's to the point of wet-fouling the plug and, of course, run sour. I've had tight clamps but still had a boot hung up on the back side and subsequent bad high rpm performance.

Oh, and is the choke turned fully off and all choke linkage functioning?

[Sparky51]

I will doublecheck that, thanks.  Tank is still off. So I can get back in there and confirm.    I did pull the plugs after the ride and all were nice and dry.   

Thanks

[Bighead]

The fuel lines need to be EXACTLY the length of the old ones and yes a rise in it will cause your problem all must flow down hill.

[Patrick]

Haven't heard back yet, but, it sounds like a classic fuel starvation problem.
Gravity feed systems are fussy. The fuel lines have to correct. But, so does the petcock.

[Sparky51]

Today's update.  When reassembling the heat shield after installing the carbs, it was apparently not "HOME" BS I followed your suggestion and found a small kink in the #2 tube, air box was not all the way down in the front due to the heat shield.  #2 tube was not all the way down on the flange like you supsected.   Tugging on the heat shield got it down some, then the air box settled down maybe 1/4 inch, and the tube from air box fits down much better. So that is at least one small part of the problem.  (Hindsight also reminded me that #2 cylinder needed more tweaking during synchronization than every other one, so  maybe it was telling me something.

I am not delighted with the routing / slope of the lines to and from the fuel line Tee.  So off comes the box this weekend so I can get in there and true things up, then go for a test ride again.  Sure would be nice to have an AC'd garage in this 92 degree Houston heat! Thanks guys, will keep you posted.