adjusting floats on Holley
 

I am wondering when adjusting the floats on the Holley, is it necessary to have the engine running with a electronic fuel pump?
Obviously with a mechanical pump, the engine needs to be on.
thanks for the info

My best guess would be yes the engine needs to be running so that it can use the fuel in the bowls otherwise one would not be able to see the fuel level move down when making adjustments. If the fuel level is low in the bowl then adjusting it up without the engine running would enable one to see movement but I think the actual level would change with the engine using fuel from the bowls!
I am no expert but this is what seems correct to me!!

Anybody else have a definite yes or no??

Do it with the engine running. It's all about the balance between fuel in and fuel out. You'll find that if you make the adjustment without engine running, fuel level will not be high enough . . . it's all about the balance between what's entering AND leaving. Look at it like a balance, balance between fuel leaving the float bowl and fuel entering the bowl. Simple, right:JEKYLHYDE

Definitely with the engine running. The above replies cover the reasons. I know because I tried it once with the engine off and I used an electric pump. Took me about a mile to figure out why the car wasn't pulling well as I gained RPM.

Ron :)

Sorry to disagree (slightly).

Turn the engine off.
Remove both sight screws, and gently nudge the car ... if gas just trickles out of the sight hole, the level is correct. I hate fires and gas stains on manifolds.

If nothing comes out of the sight holes, adjust the screw no more than 1/8 turn and lock it down (actually, maybe a 1/16 of a turn will be enough). Start engine and nudge car after 30 seconds or so ... if gas trickles out of the sight hole, the level is now correct. If not, repeat 1/16 turn of screw and recheck.

If the gas continually flows out of the sight plug hole, the level is too high. Of course, you have a rag under the carb to collect the gas and reduce the chance of a fire???? Turn off engine. Put sight plug back into bowl, adjust level screw 1/16 turn.

a) Remove one of the bottom screws that hold the secondary bowl to the carb (use paper cup to keep gas off intake manifold). Remove a couple of ounces of gas. Reinstall screw. Start engine and let it idle for a minute. Remove sight screw and nudge car, etc.

OR

b) For primary bowl, start engine to use up the excessive gas in the primary bowl. Remove sight screw and nudge car, etc.

OK, now both bowls are correct. Take the car for a 5 minute drive. Park on level ground and check both bowls again. Why you ask? That is because 90% of people make a LARGE 1/2 turn or greater adjustment and still have the level screwed up. Small adjustments only.

Forgot to mention an important point: Fuel pressure supplied by the pump, be it a mechanical or electrical pump, tries to push the needle off its seat and the float down. Consequently, the balance between this pressure and float buoyauncy must occur as you're adjusting the float. As been said, the engine and pump need to be operating during float adjustment.

Engine off.

Fire is a bad thing - and those little gaskets under the locknut will tear and spray at the worst possible time. Can't put that genie back into the bottle if it gets out and finds something hot. Trust me on that one...

I adjust them a flat of the nut at a time - easy to guage 1/6 of a turn that way. If you are reasonably close you are plenty good enough - this ain't a religious setting. If you are close and you're running out of fuel - check the float drop - not the level. If the float can't drop enough it won't allow the bowls to fill. Usually a non-issue on Holleys but I've seen some very "creative" worksmanship over the years...

Sorry, but the engine or fuel pump does not need to be running when making the adjustment to the set screw on the top of the bowl. But it does need to be on when you are observing "the slight trickle" of gas out of the sight hole which is an indication of a properly adjusted float.

Minor point, but as I said before, I hate engine fires.