trouble setting floats on 3310 holley

[dynoflo]

i have a 468 bbc on dyno with a rebuilt 3310 that i cant get enough adjustment on needle seats to set floats to bottom of sight gauge. I t has new needle seats and brass front and foam rear floats , which it calls for. I dont know who rebuilt it. Can i bend the float linkage to set? Thanks in advance.

[PRH]

Make sure the float isn’t contacting the vent baffle.

Do the needle and seats have the correct Holley style adjustment hardware?
Some of the brand x parts store kits come with goofy needle & seat assemblies.

[NormS]

A couple things to look at.
1) The 3310 bowls should take needle and seat assemblies that are 1.450" overall length. There are some assembles that are 1.500" overall length... those may not allow you to get the fuel levels up to the bottom of the sight holes.
2) Float levels should always be set with the proper fuel pressure set first. and the fuel pressure and float levels should always be set with the engine running.

[dynoflo]

Norm-measured my needle seat and its 1.450. I dont need much too get fuel below sight hole. Its barely coming out of boosters at an idle. My problem is im out of thread and .050 would be enough. I ordered 2 yesterday and hopefully they are 1.500. Thanks for the help. Im 77 years old and never knew they had 2 lengths.

[HQM383]

Bent floats in these positions to get more adjustability out of needle & seat.

[lefty o]

as mentioned, what is the fuel pressure. with too much pressure the needle and seats will never shut off the flow. no need to bend float linkage on a holley style carb. jet extensions or vents rubbing on the floats, or needle and seats are junk whether they are new or not.

[NormS]

What you're experiencing, is one of the scenarios that occurs when you try to set float levels with the engine not running. Also, if you are using a conventional restriction type fuel pressure regulator, fuel pressure will creep up to whatever an electric pump is putting out, if you are not running the engine. So setting fuel pressure and float levels should always be done with the engine running. So as lefty said, check your fuel pressure, and do that with the engine running. 6 -6 1/2 psi is what you should have. Then, set float levels.
The order in which you do basic tuning steps is important.
1) ignition timing
2) fuel pressure
3) float levels
4) idle speed and idle mixture, with the engine fully warmed up

[DCal]

What you're experiencing, is one of the scenarios that occurs when you try to set float levels with the engine not running. So setting fuel pressure and float levels should always be done with the engine running. So as lefty said, check your fuel pressure, and do that with the engine running. 6 -6 1/2 psi is what you should have. Then, set float levels.

Norm please explain the exact procedure of setting the floats with the engine running. And I'm not being sarcastic in the least, I just want to do it right. My engine has a lumpy cam and shakes a lot at idle so I adjust it with the electric pump and the motor off because I've had an engine bay fire before and it scares me.

[MadBill]

You could just temporarily crank up the idle to a smoother RPM.

[DCal]

You could just temporarily crank up the idle to a smoother RPM.

Happier is he who can prevent the cause of things.

[lefty o]

if fuel spilling out of the float bowls while running with the plugs removed, get some of the clear float level plugs.

[DCal]

if fuel spilling out of the float bowls while running with the plugs removed, get some of the clear float level plugs.

I have some so I will try those for setting the floats and put the brass plugs back in before hitting the street. Thanks for that suggestion.

[Schurkey]

The last time I couldn't get the float level LOW enough, I had problems with the stupid O-ring on the seat assembly.

The rubber O-ring hardens and flattens, and then it doesn't seal. When the leakage is minimal, the float level goes high. When the leakage gets worse, the fuel blows out the vent tube.

Holley didn't--and maybe still doesn't--sell just the O-rings. You have to buy a kit with the O-ring, gaskets, and a screw.

I bought a hundred of the appropriate-sized O-rings in Viton, from the company that used to be Small Parts, Inc. They got bought-out by...Amazon, maybe. Viton is more resistant to cold-flow (taking a permanent set "flattened" to the wall of the float bowl casting) and wonderfully gasoline resistant.

Don't set Viton on fire, though.

[NormS]

Setting float levels with the engine off, requires you to submerge the floats much deeper in the the fuel to try to control the fuel levels. If you are using an conventional regulator, doing that with the engine off will also, most likely, give you fuel pressure that is much higher than you want, due to the seepage rate of the regulator, and the fact that the engine is using no fuel. It takes a small amount of fuel usage to satisfy the seepage rates of the regulator and the needles and seats. What the engine uses at idle should be more than those seepage rates, assuming that the regulator, needles and seats, and the floats, are in good shape.

Once the fuel levels have been set with the engine off, those fuel levels will most likely be way too low once you start the engine. That, of course, will make the engine run too lean under power, and even at idle. So setting fuel pressure and float levels should always be done with the engine running. So set your fuel pressure, with the engine running, at 6 -6 1/2 psi Then, set float levels, also with the engine running.

The order in which you do basic tuning steps is important.
1) ignition timing
2) fuel pressure
3) float levels
4) idle speed and idle mixture, with the engine fully warmed up

Do not use those clear plastic screw in sight hole plugs. They give you a very inaccurate setting of the fuel levels, usually much lower than you think they are. If you are too uncomfortable with having the sight plugs out while the engine is running, then buy a pair of bowls that have the clear glass sight windows. But if your engine is shaking pretty hard, setting the fuel levels, even with those bowls, may not be very accurate, because of fuel sloshing inside the bowls.

I suspect that the shaking is from not running enough initial ignition advance at low rpm's, and from your butterflies being too far open at idle position. Correcting those issues may smooth the engine out enough to get good accurate fuel level settings. You may need air holes drilled in the butterflies to get that those butterfly idle positions right. But that should be done only after getting your initial ignition timing set right, to suit your camshaft, compr ratio, and fuel octane. This stuff needs to be done before those basic 4 tuning steps.

[DCal]

Once the fuel levels have been set with the engine off, those fuel levels will most likely be way too low once you start the engine. That, of course, will make the engine run too lean under power, and even at idle. So setting fuel pressure and float levels should always be done with the engine running. nSo set your fuel pressure, with the engine running, at 6 -6 1/2 psi Then, set float levels, also with the engine running.

The order in which you do basic tuning steps is important.
1) ignition timing
2) fuel pressure
3) float levels
4) idle speed and idle mixture, with the engine fully warmed up



I suspect that the shaking is from not running enough initial ignition advance at low rpm's, and from your butterflies being too far open at idle position. Correcting those issues may smooth the engine out enough to get good accurate fuel level settings. You may need air holes drilled in the butterflies to get that those butterfly idle positions right. But that should be done only after getting your initial ignition timing set right, to suit your camshaft, compr ratio, and fuel octane. This stuff needs to be done before those basic 4 tuning steps.

Thanks Norm. I put in new spark plugs, got new needle and seats, checked timing and fuel pressure and checked cranking compression, also checked the ignition box and coil. I warmed it up and set the floats with engine running and adjusted air/fuel mixture screws and by butt dyno this 3310-4 hauls ass compared to the HP950 which normally is on this engine. This 750 carb has been on the shelf for 9 years since I built this street 565 engine. I wanted to have the 750 around for an upcoming SBC dyno session. I'll revisit this 950 later. Thanks again.