Return fuel line with Holley 600? Regulator with return?

ewokracing

ewokracing

Active Member
Hi all,

If you're running a Holley and still have the original fuel return line, did you plumb it in somehow or just leave it disconnected?

I was thinking:
- run factory line to Holley
- filter in engine bay between nylon line and Holley
- fit a Holley 12-842 fuel pressure regulator, which would allow excess fuel to run back to the tank via the factory return line

Fuel line to engine bay, fuel regulator, filter, fuel line to Holley.

Thoughts? Or on the 600s is there a return circuit on some models (I did a quick google and by the look of it, they're all deadhead carburettors). Mine is a 600cfm 1850(1)
 
I ran an Autolite 4100 four bbl on a 4.6 and left the return disconnected, never had an issue with it.
 
Your plan sounds good. You need just enough pressure so the carb doesn't lean out at higher revs under load. a 600 flows about a cubic metre per second of air. coming close to double what a little 3.5 litre can breath at max RPM so you will need to be careful about lean out.
 
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