GO4BROKE

Bad-Habit you've got mail dude!

Checkmate 454 Mag-these webers/edelbrock/carter/merc have upside down floats, the needles and seats are in the top of the carb.

MACDAD260- You're right float level adjustments are supposed to keep the float bowl level correct and have nothing to do with the mixture. All I know is that its not true of this carb. I had 1 motor fouling plugs and blowing black smoke, I adjusted the floats, NO other changes, and the problems solved. I set the floats on the other motor just to be safe as it was running fine, and now it has much crisper throttle response. Both the float adjustments on hese carbs are critical to having the right mixture. I don't understand it, but it's my experience.

Vinny P

I didn't mean that the float level has anything to do with the mixture. But, it can cause the motor to run rich if the level is too high or lean if the level is too low. It does this either by causing the bowl to run dry while the engine is under load due to low float settings or spill fuel into the venturii if the level is too high causing a rich condition..

FloridianSon

The AFB float setting is checked by inverting the carburetor top and measuring from the gasket to the top of the float.It should be 1 9/32'' with 5 psi of fuel pressure and 1 5/16'' with 8 psi fuel pressure.

MACDAD260

Guys, Please carefully re-read my post. There seems to be some misunderstanding of what I said. Maybe some of you are confused because you are not familiar with the Weber/Edelbrock carbs. I'll try again to explain the difference between the upper and lower float settings.

In the first picture, Bad-Habit is showing the float in the position it will be in when the top is bolted to the carb. The float "drop" is nothing more than the effect of gravity on the float when there is no fuel in the bowl to "float" the float. "Drop" has no effect on fuel mixture. There is an adjustment that limits the amount of "drop". You do that by bending a tang on the pivot side of the float. I believe the measurement is 1" to 1 1/4". This is not a critical measurement. Just set it to the spec and forget about it.

The second setting is the important one. It is the distance the float is lifted up by gasoline in the bowl before the needle is closed. This sets the height of the fuel in the bowl which has a very critical effect on the fuel mixture. Since there is no way to adjust this setting while the carb is bolted together it must be done with the carb apart. Also, since you cannot use the fuel in the bowl to lift the float you need to simulate this by turning the top of the carb upside down and using gravity to pull the float down. The distance between the float and the airhorn gasket is the float "height" I have an Edelbrock carb tuning sheet that says this should be 7/16". On my own Weber carb this measurement is more like 5/16". Your spec may be different. The important thing is to have both floats adjusted to the same height. All other things being equal, a higher float level will richen the mixture, a lower float level will lean out the mixture.

Now that the floats are adjusted you can begin tuning the carb. This is done by a combination of jets, needles and springs. A large jet or a thinner needle will let more fuel flow, thus richening the mix. Smaller jets and thicker needles will lean things out. The springs that control when the needles open have an effect, also. A stonger spring will start to lift the needles sooner which will richen the midrange. A weak spring will lift the needles later which will lean out the midrange. WOT is controlled mostly by the main jets although float height and primary jet size must be correct, too.

If you think your engine is running too lean, start by increasing the jet sizes by at least two. If that seems to help, try going up again and again until performance starts to get worse. Then go back to the setting that made it run the best and you should be right on. It will take time but it is the only way to get it right. Good luck.

BAD-HABIT

MacDad....I read your last post and am wondering something. How can the amount of drop not effect the amount of fuel in the bowls? I mean the smaller the drop the more fuel that is allowed into the bowls before the float begins to limit the fuel. Isn't the float level (Inverted float measurement) then important because it decides WHEN to limit the fuel? From looking at this thing all weekend I belive both settings are important. But I am just a layman...I am going to call Edelbrock today and get the "Scoop" I will let everybody know what I find out.

BH

David

Bad-Habit: Macdad260 has it 100% correct. The critical setting is when the top of the carb is held upside down, and the distance measured from the float to the airhorn gasket. That is what controls the level of fuel in the bowls, and has a bearing on air/fuel ratio. You should find a spec on the reference sheet you have for the carb.

BAD-HABIT

Well after speaking to the tech gods at Edelbrock they stated that yes the float level was the most critical measurement. But they also stated that an exessive drop like mine could also cause problems. He stated it would have to be an exessive amount though....I called Jegs and ordered a set of HI-FLOW needle and seet asmblys. Arcorrding to jegs the amount of fuel that the bowl will hold will stay the same BUT that since the dia. of the needle and seat is larger the fuel will flow faster. Figure this can't hurt and considering that they were out of stock of the stock needle and seat asmbly. I said sure. I had noticed that if the carberator was inverted that the needles would stick even though they were cleaned. Now when I say stick I mean barely. One would do it every time the carb was inverted and the outher only sometimes. Now all it took for the needles to unseat was me (full of hot air anyways ) blowing into the fuel inlet hole to unseat them. I figure that any amount of fuel pressure at all would open the needles so I don't think it is part of my problem but hey If I can eliminate one more thing Then I figure one problem down 10 thousand more to go

BH

MACDAD260

Bad-Habit,

Glad you found the answer you were looking for. Now all you have to do is figure out the jetting that will make it run strong and live, too. It never ends, does it. Good luck.

BAD-HABIT

MACDAD260 I lay the Golden Wrench at your feet
Actually It's not a jetting problem. See my post "Running LEAN" a few posts back in the tech area. Im leaning towards a fuel delivery problem or vaccum leak....By the way what is the easiest way to check fuel pressure at the carb? And what should it be. Should I check at idle,W.O.T. or both? Im running a stock carter marine pump with the metal tubing from the pump to the carb....

Thanks
BH