Fuel line/pump too small? Crappy carbs??

Still having issues with my 506ci dual quad Ford. What it does now is it will run fine for a while, great actually, then after it gets warmed up cruising around, the idle gets real sloppy when you have it in gear (auto). It keeps jumping down and back like it wants to cut out. Then in your cruising along and you gradually start getting on the throttle kinda deep, it will skip, sounds like shit. Now the fuel line is a small stock piece all the way back to the tank, and the pump is a stock 429 pump. The carbs are old Holley 600's that have been professionally tuned as best as they can, but still, I know there not that great. Where shoudl I start? I can't find any vacuum leaks, it has to be some fuel delivery issue?... Thanks alot,
-Dean

 

if its an old tank has it ever been cleaned? if not its possible that the fuel pickup strainer in the tank is clogged with crap//also if it needs a vented cap and you have an unvented cap it could cause a problem too

 

You should be running 1/2 fuel line, and a high volume fuel pump for starters. I'd try that first

 

Need vented tank or vented cap. Frank

 

If it aint a race car you don't need 1/2 in line. My ol Ford was running 12's
in the 70's with 5/16" line. It got change later on but it still did the job.
The 600's suck. Check for crap in tank and carbs. Plus vents

 

No offense intended, but do you really need to ask about running 506 dual-quad cubic inches through a stock fuel line? You're about a hundred inches and one whole carburetor beyond it's ability.

Regarding this whole "not-a-racecar" deal ^.......tell that to your engine when it's leaned out in 3rd gear on the street. Just say "Don't worry about your dangerous air fuel ratio, you're not on the track". Everything will be fine, physics can be defied with soothing words

 

Never heard of having too big of a supply line.

 

Would have been 11's if it was getting enough fuel!

 

3/8 th's fuel line should feed that motor just fine just start at the tank and keep going til you hit the carbs

 

I run a Holley blue pump, 1/2 inch line and 6 PSI on my 2 x 4 set up. The carbs are 450 cfm each. On the interstate with a 700R4 I still get 18 MPG if you don't get stupid.