What's the opinions on Holley style carb float adjustment with the brass plug style fuel bowls and center hung nitrophyl floats. Set the floats dry with the bowl upside down using a drill bit or on the car with the engine running to just the bottom of the sight hole?
Anyone use a spring on the center hung float?

I set mine dry, upside down with a 7/16” drill bit.

It’s difficult to do it wet with removable sight plugs and a non-electric fuel pump.

quote:

Originally posted by Lenny5160:
I set mine dry, upside down with a 7/16” drill bit.

It’s difficult to do it wet with removable sight plugs and a non-electric fuel pump.

I also use this method. No spring on float. I do check the level at the plugs afterward, with the pump running. The level is usually just below the openings. I bump the rear bowl level up to where it just starts flowing over the threads. I leave the front bowl a touch lower. Those 2 are old habits from way back. The thought was to keep the front lower to prevent fuel from sloshing out the bowl vent into the primary throttle bores upon launching. Using vent tubes probably eliminates that issue anyway. And the high level at the rear bowl was to prevent the jets from sucking air when the fuel surged back away from them during launch. Jet extensions take care of that issue. So there really is no need to do all that with rear jet extensions and a tube across the bowl vents.

I've read where some set the rear with a 3/8" drill bit and the front with a 7/16 to keep the rear bowl fuel level higher.

I like upside down and measure from the roof (bottom) of the bowl to the seam of the float. Primary .750 and secondary .850

quote:

Originally posted by Eman:
I've read where some set the rear with a 3/8" drill bit and the front with a 7/16 to keep the rear bowl fuel level higher.

I could see that. I used to use 3/8" for both, but it was right on the edge of running fuel out the primary at idle. An uneven pit spot would make it drip.

quote:

Originally posted by SP 124X:
I like upside down and measure from the roof (bottom) of the bowl to the seam of the float. Primary .750 and secondary .850

3/8" drill bit never fails for me

The only fine adjustment for me is clocking the window in the needle and seat so it is facing the fuel inlet.

This message has been edited. Last edited by: TomR,

Interesting that, if you don't set primary and secondary heights the same, some are setting the secondary higher and some are setting it lower.

quote:

Originally posted by SP 124X:
I like upside down and measure from the roof (bottom) of the bowl to the seam of the float. Primary .750 and secondary .850

Are all of the floats the same using this method? Seems easy enough to cross check between the drill bit and the seam method for comparison. With the drill bit it always touches the edge of the float closest to the needle.

Now we go to the next question concerning floats. I have read a carburetor builders comment that he recommends float adjustment to change for lean/rich condition so no need to change jets for weather or seasons. Opinions?

quote:

Originally posted by Eman:

Now we go to the next question concerning floats. I have read a carburetor builders comment that he recommends float adjustment to change for lean/rich condition so no need to change jets for weather or seasons. Opinions?

Float level does make it a little richer or leaner. I do not change jets or float level for seasons or altitudes. When a carb is set right it really self adjusts for weather. The thicker, denser and more volume of the air is the more fuel it pulls with it. I am actually going back to carbs on all three of my race cars for next year and will have O2 data on them to know more.

One thing to be aware of if you are having problems with float level check your fuel pressure and I recommend putting new floats on every year.

Yep, floats get saturated and heavy over time. If you suddenly need to adjust your floats, you're better off pulling the bowls and finding out why they need to be adjusted. Trash in the needle and seat or heavy float that won't allow the n&s to close properly.

Yep, I begin every season with new floats.

It's really the only time I look at the carburetor.

Final adjustment is always with the sight plugs, secondary over the bottom of the hole, primary just at the bottom, not running over.

Float level can affect the emulsion and main well feeds.

Cant find the float adjustment on this Enderle injection hat..... Am i doing something wrong?

quote:

I like upside down and measure from the roof (bottom) of the bowl to the seam of the float. Primary .750 and secondary .850

X2

Bob

quote:

Originally posted by SP 124X:
I like upside down and measure from the roof (bottom) of the bowl to the seam of the float. Primary .750 and secondary .850

Isn't that just the opposite of setting front with a 7/16 and rear with 3/8" I would have thought you wouldn't want the primary float higher.

Put new floats in and set the frt. at 7/16 and the rear at 3/8. Started the engine and checked for leaks and let it idle and opened the brass sight plugs. Frt. was below the opening by about a 1/16", rear was dribbling out the opening.
Inspecting my old frt. float it did have a split in it, it was a Braswell wedge shaped float.

Thanks for the follow-up post, Eman.
Sounds like you've got them set right where I would want them to be.

What type of floats did you go with? The grey nitrophyl?

I bought a pair of nitrophyl floats from ATM, they are black. They are wedge style and both have the cutouts for jet extensions, ATM epoxied the seam where the arm attaches. I weighed them and engraved the weights on the steel arm of the float. I also had them send a set of gaskets, they are nice heavy pink colored gaskets. I had blue gaskets and have had some peel when they come off.