Between running a Holley instead of the Q-jet, and the price of the stock AC gas filter GF-432, I'm going to give the stock Holley inlet filters a try this summer (they were already in the new carb I bought last fall). I'm trying to plumb up a similar type return line (from the dual outlet line hooked to the Holley), but I don't want to risk losing too much fuel pressure. I'm just curious if anyone knows if the original fuel filter (GF-432) had a restriction orifice in the return nipple, or if the system just relied on the flow resistance of the nine foot return line.

Any insight here is appreciated.
Thanks.

 

Given that it's advertised as a vapor return line I would guess that it's restricted. I do know that when I plumbed a fuel log that in effect had no restrictions my fuel pressure ended up approximately cut in half or at least cut by a whole lot. That's for the stock line sizes (from my memory of a couple of years back).

That's about all I can offer, my system's now way different.

 

Well, right now I'm considering using some bulk brake line tubing (1/16" ?) I have laying around for the return line. Nine feet of that ought to be sufficient restriction to minimize the pressure loss at the carb, but still allow a bit of recirculation and a fast pressure bleed off when I shut the engine off on a damn hot day.

I remember capping off the return port on the tank about ten years ago when I transferred the tank to the new/modified frame, but I don't recall where that port is. (Do you happen to know where it is?) Hopefully I can still reach it with the body back on.

 

1/16" line sounds like it would work. Pressure drop probably is just a ratio of areas. You can reach the return from underneath if you drop the muffler. Doubt that you'd have to drop the tank.

 

I'm assuming the vapor return location is that hose at the upper right of the tank. I appreciate the photo/help.

 

Mike -
There is a restrictor orifice in the fuel filter return nipple. It's easy to duplicate the system on the dual feed Holley by installing a plug-welded fitting in the line and drilling a .060" diameter bleed hole in it. This does not affect fuel pressure, and it assures a constant flow of fuel through the system to eliminate vapor lock. Here is a system with a constant bleed orifice that I installed on my son's 463 Pontiac. It works well:

The -6 to -4 reducer at the far left of the system has been plug welded and drilled with the .060" hole.