My Holley 40458 is giving trouble. I couldn't adjust the secondary float level (counterclockwise to raise level) to be high enough to be just below the sight hole. Finally I got tired of trying to adjust it and took the back bowl off. The float was adjusted all the way against the bottom! So I turned it upside down, adjusted it so the float was level with the bottom, put it back together, and took it for a ride. Now the level is way too high. So I loosened the screw and turned the nut clockwise, again and again and again, and still the level is too high. What is going on? I could be wrong, but the nut never feels like it's engaging the needle to turn it. Why didn't my dry adjustment work? Did I bend the float tang?

The float may be full of fuel? so no amount of adjustment is going to correct it, the black plastic floats are really susceptible to becoming fuel logged, even brass float can develop pinhole leaks and take on fuel, fooling the needle seat into a "low" fuel need, when in actuality the float level is to high...is fuel being pulled over into the secondaries at idle? visible while looking down the secondary throat at idle?

This float is yellowish, almost orange, plastic float. No fuel in it.

Hollow float or solid plastic?

The threads in the bowl might be stripped which would explain why it won't hold an adjustment or the needle valve isn't shutting off the fuel flow.

You have to adjust the secondary side very slow. Especially lowering it. The secondary bowl uses fuel at a much slower rate.

If I'm in the same spot as you, I turn the engine off and drain a little fuel out of the bowl through the fuel screw. Enough so it's below the hole. Then turn the adjusting screw 1/2-3/4 turn down and start it again.

If it's still high, repeat. If it's low, adjust it up very slow and you'll get it.

The threads are not stripped, the nut has 2 flat spots in it. When it falls down too far, then the flat spots dont engage.

Silly question, is CW and CCW opposite directions from front to rear bowl?

Same front to rear.

Pull up lightly at the attachment where the vacuum secondary diaphram rod connects with secondary linkage. Engine idle will come up and you will be pulling more fuel from the secondary bowl.


If you adjust it down when it's full, this is a quick way to lower the bowl fuel level.

That's a good tip, will try it. I still think I'm going to end up taking the bowl off again to see whats going on.

There's nothing wrong with bending the tab if you can't move the seat far enough to set fuel level.

R.

Yep,that is an easy fix,all you need do is run the needle/seat in until you have about 1/16" exposed above the bowl,bend the tab until top of float is parallel with bowl and you will have all the adjustment you need up or down to get the correct float level.

I took the bowl off today. The float was adjusted all the way down again to where it was sitting on the bottom. So if gas is still pouring out of the sight hole, that means I got a needle and seat problem, right? thnx.

be sure to check your fuel pressure, also. try another needle/ seat assy. my favorite abbreviation, fwiw- assy. i always feel like i'm getting away with something. assy.

Found a piece of gasket between needle and seat. Arghhh!

Good find Easy fix huh

HELP! THIS MAKES NO SENSE AT ALL! My secondary bowl is still overflowing through the top adjustment screw (and out the sight hole if I loosen it to check).
I assumed I fixed my overflow problem when I found the debris (see above post) between the needle and the seat.
But today I took it for a ride and its STILL overflowing. So first I made sure the o-ring was ok, THEN I REPLACED THE ENTIRE SECONDARY BOWL WITH ANOTHER I had laying around (of course I did the dry adjustment on that before installing it), AND ITS STILL OVERFLOWING. So I'm assuming there's there's 1) something wrong with my secondary block and gasket, 2) or too much pressure coming through the balance tube from the primary side.? Is there a pressure regulator anywhere inside a 80458 holley carb? Or is my nearly brand new fuel pump suddenly putting out too much pressure? What else could it be?

There is no pressure regulator on any carb of which I am aware.

Pressure cannot be added between the front and rear bowls. As they are hooked together in parallel each sees exactly the same pressure.

A metering block can only reduce pressure, not add. If there was something wrong with your secondary metering block, that side wouldn't be getting any fuel. There is an exception to this, and that's if you have a secondary power valve with a ruptured diaphragm, fuel will steadily run into the main circuit.

When you say overflowing what do you mean exactly??? Where do you see the fuel coming out?

There is a gasket between the float setter hex and the bowl. There is another smaller gasket under the lock screw. These have been known to leak.

R.

The "o" ring on the needle adjustment is bad. Just had this happen.

The gas is pouring from between the float setter hex and the adjusting screw, but - that's just the path of least resistance. The real problem is the bowl is too full of gas - no matter how much I adjust the float it doesn't make any difference.
If I open the secondary sight screw it pours out there too.
My best guess at this point is gas is pouring out a small hole in the gasket between the secondary metering block and the metering plate that screws to the block. My other theory is that one of the screws (not a hex screw, not like any screw I've ever seen) that holds the metering
plate was loose, and gas is seeping past that screw.
Either a bad gasket or a loose screw would render float adjustment useless, right?
I gotta wait to find out if I'm right, 'cuz I couldn't take the gasket off in one piece, and had to order another one.
Bigcar, you may be right, but remember I swapped in a whole new secondary bowl including the needle valve and the seat, so that would mean I had two bad needle and seats....not impossible, but not likely either.