[chiphead]

OK this might sound like a stupid simple question, but what is the proper way to check the fuel levels in a holley double pumper?

My engine started running really rich for no reason, dipping down into the 10s on the AFR meter at light cruise. I took the bowls off and found I had improperly installed the float spring in the primary bowl. No dirt or contaminates were found in bowls or filter. The needle/seat assembly is less than a year old. I rebuilt the carb last summer. I cleaned and inspected everything before I reassembled it (correctly) this time.

This is a modern QF copy with the large sight windows in the bowls. I assume the fuel level should be in the middle of the window with the engine warmed up and running at idle?

The gamut of instructions on the net don't clarify if the engine should be running when the final fuel level is verified, after the adjustments are done and snug.

[1969GTO]

just my 2cents: I was taught fuel level was set, engine idling and fuel level set just to the bottom of the site glass.
In the Old Days we had no site glass, just remove the brass plug on the side of the bowl, set the fuel level, and that's it.

[Formulajones]

I check it running.

Original Holley bowls had the front bowl sight screw higher than the rear bowl sight screw. Many don't realize that.
Aftermarket stuff I haven't seen that. Just an fyi. The level will change the AFR slightly, but not a crazy amount like you're seeing.

I initially set them with the bowls off the carb. Flip it upside down and look at the float. Turn the adjustment nut until the float is nice and level. Done.
Can be tweaked from there after it's running but I don't always find a need to

[Dragncar]

Old school bowls you want the fuel at the bottom of the hole. or it will run out.
Newer stuff with the sight glass you want it in the middle of the glass.

[ta man]

Old bowls I always set them for a slight dribble out the front ..and a slight dribble out the back if if bounce the fender.

[Skip Fix]

Originally Posted by ta man

Old bowls I always set them for a slight dribble out the front ..and a slight dribble out the back if if bounce the fender.

Yep me too.

[Kenth]

Holley's Achilles heel, besides the 20 or so places they can leak fuel, is the power valve which either hardens and gets stuck in the open position or softens and cracks so that it is wide open.
No amount of float adjustment in the world will help here, only a new correct power valve can cure the problem.

FWIW

[chiphead]

Funny you should mention that. The only other change I had made on this test drive was going from a 9.5 to a new 10.5 PV. I had tied the secondaries shut and was tuning on the primaries only. I re-sized the emulsion bleeds to .026 upper and .0275" lower with a .027 HSAB. 71 primary jets, .058" PVCR.

The main circuit AFR is great at cruise, moderate accel and WOT. Right at 13.5 AFR 2500 RPM cruise and 12.8 climbing a steep hill. At heavy primary between 9" to 6" of vacuum, the AFR goes to 16.x and it tries to ping a bit. I pulled 2* of timing this past summer around peak torque, that seemed to fix it. WOT on primary only is 12.1 AFR, I'm happy with that.

Going to the 10.5 PV keeps it in the 15s AFR and the engine's response doesn't "go flat" as I roll into it. Previously it would get lazy when the AFR goes above 16 AFR and I was rolling into the primaries. Then on the way back home it went pig rich for no reason. I checked that the 10.5PV was not blown with a vacuum pump. Only thing I saw is the primary fuel level was low when I got home and I could see fuel flowing over the float through the sight window while it was idling. Secondary bowl level was fine. That's when I took it apart and found the primary float spring installed wrong. I'm really hoping that was the cause.

[Holeshot71]

Floats that start taking on fuel can cause a sudden rich condition.