Holley 3810 Fuel Bowl Float Setting

[Gerard F.]

Getting down to doing final adjustments on my 67 carb with non-externally adjustable fuel bowl floats and am getting confused with the specs.

The 1967 Chassis Service Manual, and Chassis Overhaul Manual (which has a very thorough adjustment procedure), both have a spec chart (Section 6M) which indicates the following specs for the fuel bowl floats:
Primary .17"
Secondary .30"

Yet the Holley Illustrated Parts and Specs Manual (36-15-7 circa 2002) indicated for a 3810:
Primary 5/16" (.3125")
Secondary 11/32" (.3438")

A 1986 carb kit instructions for a 3810 indicated:
Primary 5/32" (.1563")
Secondary 5/16" (.3125")

Yet a newer generic carb kit I have indicates the same as the Holley Manual for the 67 4160's:
Primary 5/16" (.3125")
Secondary 11/32" (.3438")

There's quit a difference in the specs, especially for the primary side. I'm tending to go with the newer Holley spec, assuming there was a flooding problem with the original 67 spec and it was later changed.

Any thoughts on this?

[Timothy B.]

Re: Holley 3810 Fuel Bowl Float Setting

Hi Jerry,

I set mine at 5/16" with a drill bit at the float toe. When finished, the float will look just down a tad from even with the top of the bowl.

Don't be afraid to put it where it's supposed to be as most flooding problems are a result of something else. The quality of todays gasoline will expand and boil much faster but with the hot slot pluged under the carburetor and a secondary idle circuit I bet you don't have any problems.

[Joe C.]

Re: Holley 3810 Fuel Bowl Float Setting

Jerry,

You know that the fuel pump pressure will cause a fairly significant variation in actual fuel level in the bowl(s) with the same dry float setting. The only way to actually verify this is, as you know, by means of a sight glass or plug, which are not available to you.

I would first check my fuel inlet pressure (both static and dynamic), with the engine hot and running (fuel pressure will vary a couple psia based on engine temp). Based on that reading, I would "tweak" the dry float setting from the average reading that you're finding in the various publications.

For example, if the fuel inlet pressure turns out to be on the high side of the prescribed range (about 7 psig) then set the dry level to seat the needle at the low value of the ranges found. If pressure is on the low side of the range (say, 3 psig) then have the needle set at the high float level of the range.

Before I rebuilt my fuel pump, I had the float set (wet with sight plug on the 4150) with an idle fuel inlet pressure of 1 psig!!!!!!!!! I was using the car like this for a couple years, and never had a driveability issue. In fact, I never knew that I had low fuel pressure until I decided to put a gauge on the fuel line. It turns out that the outlet check valve in the fuel pump was dislodged from the casting!

Hey.....why not drill sight plug holes in yer float bowls. You can then use some Bazooka to plug them. Maybe even some dessicated jizzum, which has the pliability of "dum-dum". Undetectable if done right.