Anyone discover a fuel friendly float setting?

[IPM]

I rebuilt the carb and set the float a tad lean at 13/32", stock is 3/8 or 12/32. Still seems a bit rich and could trim it down some more. Anyone?

[overlander63]

Originally Posted by IPM

I rebuilt the carb and set the float a tad lean at 13/32", stock is 3/8 or 12/32. Still seems a bit rich and could trim it down some more. Anyone?

The higher the float level, the more fuel is in the carb. If it gets too full, it will overflow. If I am reading what you wrote right, I think you have it set a tad high, try setting it to the spec provided, and see what happens. Also, what kind of carb do you have? Quadra-jet, Holley, Edelbrock(weber)?
Terry

[IPM]

downward, from the mating surface, into the body of the carb, so the greater the distance, the leaner the settig. Went camping and it drove great with the carb rebuild. Also added Mr. gaskets distributor advance kit with weakest springs and that halped alot aS WELL.

[IPM]

In case anyone is curious the float setting I used seems fine. Engine runs well. Also, for those wondering if a quadrajet has a power valve, it does. It's attached to the metering rods that run into the primary jets. One is not suppost to alter the screw that limits the powervalve downward travel, but I did. I leaned things up just a tad. The scre is not on some models, or located internal, or located externally on others.

[59toaster]

Float setting on a Quadrajet has ZERO to do with mixture.
Hit your local Autoparts store or Amazon and pick up a book by Doug Rowe called Rochester Tuning and performance (or something close to that.)

Mixture on the Quad is three parts.
#1 is idle mixture is set by the two screws at the base.
#2 Off idle to about 2/3-3/4 throttle is the pimary metereing jets. There is a several way's they can be effected. First is the jet size. Second is Metering rods diameter and taper. Third is the Vacuum signal.
A vacuum leak in the correct place can acually make a Quad run rich. The Primary metering rods are kept closed by Vacuum at idle. As you open the throttle the intake vacuum drops and the metering valves raise. In a deceleration state th vacuum causes the rods to be sucked closed to prevent back fires.

#3 is the tennsion on the spring that controls the secondary top door. Too little spring tension and they will open too soon and cause a over rich conditons from 2/3 3/4 to full throttle. Too little and they will open to late and too little and cause a lean issue above 3/4 throttle.

The only things the float level does is prevent the fuel bowl from running dry or over filling and the amount of fuel needed to richen the mixture by the accelerator pump when you take off from a start. That pump fills the gap from idle till enough vacuume runs through the venturie to draw the fuel up from the bottom of the float bowl. The quad will run with no accelerator pump. It just will stumble on acceleration. If your easy on the throttle you won't miss it except at cold start.
That pump is where The quadra jet primarily get's it's nick name "Quadra Bog". If the vehicle sits long enough for the fuel to evaporate out of the fuel bowl the rubber diaphram for the acclerator pump will stick to the walls in the bore and get pulled off the plunger. Then it no work.

[IPM]

I agree with most all, but the fuel level does make a difference with the differential pressure across the jets. Best reread the Rowe (book). It suggests starting at 1/4 inch with float setting and tuning from there. Nice thread, thanx for responding.
Mike

[59toaster]

Your probably right. It has been a while since I have read it and tinkered with my Quads. My goals are probably a little different as well.

How are you determining your mixture? Ring on the insulator or are you actually hooking it to a sniffer or do you have a O2 and a gage in the exhaust?

I have never found much change in actual mixture at a steady RPM. I generally went with what was recommended with the cross reference off the casting and not had any real complaints that I had to change the float level for. I could see it effecting the speed that the fuel delivers going from a near idle to a 1/2 throttle transsisiont but once at cruise and vacuum equalizes it would all be metering rods and jet sizes was my understanding (need to barrow it back from my buddy and reread).

I actually ran my last two Quad equipped trucks with a high float and never had any problems getting them past roller emissions tests. Been averaging 9.5 on the Big one on 35's with 4.10's and the smaller one with 31's and 3.73 I was getting 10.7 (GPS used to figure the MPG). I like standing those trucks on the rear bumper and with the Jet that far forward in the bowl they tend not to be in the fuel past about 45 degrees. I was to the point I was going to custom make an adaptor so I could install the Quad backwards. I am aware of quite a few folks doing that with good results. Then I just decided to go FI. That will run upside down. Again not what your looking for in a MH.

While I think that is the best book available about that carb, think about where the mind set was when reading it. Its a race mindset where 1/100 of a second makes a difference between win or lose. A lot of the tuning he speaks of is for throttle response. Economy was a secondary concern that he thankfully included to round out the book.

Personally I am from the mindset that the better it performs the more efficient the burn the better economy is going to be. I don't drag race, I rock crawl and I drive it on the street. My concern is the smog station. Doing exactly the opposite that he says to do in that book, in regards to float level, has not adversely effected it there. Well within the pass range...even with the cats sort of missing.

[IPM]

of the exhaust deposits and general performance. Did not pull out the old co meter in the shop. I was going to convert to GM TBI (got all the software for tuning, eprom burner/emulator, the motes adapters, yadi yadi ya.......
But the quadrajet runs so well. I'm just going to leave it alone.

regards,

Mike

[swebster]

OK. So my Quad is sitting on the bench downstairs waiting for it's rebuild. I just finished the book you both mentioned and from what I can see a well built, properly adjusted QJet seems to be the way to go - at least on my old MH.

One other note, When I removed the carb the two rear bolts were little more than finger tight. I put the socket on there and they just came right out. Obviously, a big ole leak could be part (or all) of my recent performance issues but just the same I pulled it for at least a very good cleaning and liekly a rebuild.

I'm sure I'll understand more about this as I go but there will be questions along hte way. I'll be sure to post what I find.

[59toaster]

It's hard to beat the olde pre electric (except for Choke) quads. Darn good carb. I would keep it on the trail truck if it would run at really bad angles. It's great on the street and very reliable.

Steven. Just follow directions that come with the rebuild kit. When you disassemble have plenty o room to lay out all the parts. I try to lay thing the way they came off. Some of the linkages can be installed backwards and they will jam if you manage that. Pay close attention to the way they are before removal.

Be sure to JB weld the casting plugs on the bottom of the floar bowl(it will be in the directions where this is needed) and make sure there is not excessive slop in the main shafts. Slop there is a Vacuum leak. Decent automotive machine shop will know what to do and install some bronze bushings in it.

If the float level confuses you then start by setting it at the recomended level. The rebuild kit will come with a chart that will list the casting numbers on the side of the carb. Take into concideration there is some slop in the pivot for the float. I always measure it by lifting it lightly to try to recreate the direction that the fuel is going to lift the float (this will make sense wne you see it).

Besure to bring the casting numbers with you when you buy the kit. There is a couple different kits with different size bores in the accelerator pump.

[87MH]

FWIW --

The Digital Camera has become my "best buddy" when it comes to mechanic work. Take plenty of Macro shots before and during dismantle.

Most of the time, if I question what I'm trying to do, just glancing at a documenting photo on the "quick" screen on the back of the camera will confirm if I'm doing it right, or, as is the case a lot of the times, I have, or am about to, screw up big time.

[jimmickle]

It has been quite a while since I have rebuilt one, but one problem that used to occur with Quadrajets is "gas logged" floats. Often the floats absorb enough fuel that they barely float, so they don't shut off as well as they should. Always replace the float when you rebuild a Quad unless you have the tool to weght it and be sure that it hasn't absorbed fuel. Of course, if it has been changed to a brass float, it should be OK.

[IPM]

any vacuum leaks however. If there is a screw locating the power piston maximun down position, you are not suppost to change it. If you do change and and want to get back to the factory setting, just look at the wear pattern on the metal parts. Also, don't try to take the cap off above the powervalve. It's not in the rebuild kkit. To remove the accelerator pump lever, tap it's pin backward until the lever is clear. Leave enough space behind it to make it easier to put it back in place. You don't have to take the entire carb apart to rebuild everytime (choke, throttles shafts and butterflies, etc.) If you to be sure everything is perfect, then take it all apart. Advance auto had the best kit price for me. $15. Read the above advice, it's all good.

regards,

Mike

[swebster]

I've been meaning to get back to this post for some time. I ended up doing a bench rebuild on the QJet and installed it three weeks ago. Since then I've noticed a number of things both good and bad. I'm hoping more experienced QJet'ers will know what to do.

First the good:

• So that's what the RV is supposed to feel like coming off the line! No more bog and nice smooth power curve.

• And now the secondaries open up. Makes all kinds of power and soudns great through those headers - big smile the first time I did it

• Also - the backfiring is gone. It actually came back but I checked the mounting bolts and sure enough two were loose again. Put on a little lock-tite this time and they seem fine.

• Cold starts actually kick down on their own not...no need to "blip" the throttle to step down from high to med to idle.

Now the bad:

• It's running rich. Very rich. How rich? 6.2 mpg on round trip from Louisville to St. Louis (was getting 7.8 - 8.4 BEFORE adding headers).

• It's loading up the plugs with soot

• I broke my electric choke connecter - anyone know where I can get one?

Here's what I think is happening. Please chime in for me and offer up and an all suggestions.

On the last trip my mileage was obviously terrible. I was also getting that little "bobble" again in the power on on ramps and up hills on the way home (fine on the way out). It definately felt like cylinders were "kicking in" rather than "falling out". At least the backfiring and complete power loss was gone!

I got the plugs to the point where cyl no 2 was only occasionally firing by the end of the trip. I noticed that the engine would run on "high idle" occasionally when coming of the higway for fuel. So I suspect that the broken electric choke plug was falling off and the choke was partially closing in turn opening up the high idle circuit. I don't know much about QJets but I theorized that this was dumping raw fuel into the engine at speed. Which could be my main problem. This high idle could be corrected with a really good push on the broken plug and she'd open the choke and drop down to idle - running well again. I know - I need to replace this plug.

So here is what I did. I had already installed a new distributor before the trip. I had previously installed a new coil, cap and rotor (on the PA disaster trip). I followed that up after the St. Louis trip with a set of new Accel Extreme 9000 Hi Temp Plug Wires (tired of burning up number 8) and eight brand new Bosh Platinum plugs.

I took it out for a quick 20 mile highway test run yesterday. The "bobble" was gone and the power was great, but all eight plugs where sooty after the test run. Just for sanity I checked the compression (160 - 165 on all eight) and bumped the flywheel forward and backward while my buddy wached the distributor pickup movement for any timing chain slack - there was none.

Next I plan to pull the valve covers and check for broken springs, flat cam lobes, bend pushrods, etc. Not necessarily because I think I have an internal problem...just because I want to "know" I don't have an internal problem.

So...sorry for the long windedness. What is going on with this puppy running so rich? I think the soot is building up in a rich condition and eventually causing misfires (cyl no 2). Adjusting the float level seems easy enough (it's set to the rebuild spec now) but what else should I be looking at?

It's getting sooooo close to running really well. Now thet the ignition has been completely replaced I just need to finish off this rich condition issue.

One other thing...i still wanders on idle a little. It doesn't even register on the tach but you can hear it idle up and down. Makes me wonder if everything is firing.

OK - I'm done now - any ideas, suggestions or thoughts from anyone?

[59toaster]

With that choke plug messed up you may not be getting a good connection. Be sure that choke is fully open.

Did you play with that screw on the top of the rear door any? It sounds like the secondaires are coming in a littl etoo soo and causing your rich condition. The way that thing works is the spring tension is such that the engine has to pull enough air though the top doors to pull them open. Too little tension and you will run rich at 3/4 plus throttle. The bottom plates should not open below 3/4 throttle.

For base line idle I like to use a vacuum gage. Set idle to 650 RPM. attach the gage to a central port (thermac for the Aircleaner connection on passengerside near choke is usually a good one). adjust each screw till your pulling the most vacuum. Repaet a coupel times to fine tune. Once your pulling the most vacuum the give each screw a 1/8 turn lean (clockwise). Readjust to proper idle speed.

The reason this works is the closer you are to optimal fule mixture the harder the engine is going to pull vacuum. At idel being a little lean is fine because there is no load. The accelerator pump will gt it rich for acceleration till the mains can come online with air moving though the venturies.

If that doesnt cure it may be float adjustment time. There is a little tool you can use to see the float level without takign it apart. Should be instrucktions with the information in the rebuild kit.

[87MH]

First the good:
.........

And now the secondaries open up. Makes all kinds of power and soudns great through those headers - big smile the first time I did it

.......

Now the bad:
.........

And now the secondaries open up. Makes all kinds of power and soudns great through those headers - big smile the first time I did it

.......

Steven:

Welcome to the real world (and mileage identical to mine ).

[swebster]

Dennis - very funny!

[ALANSD]

its like that Twilight Zone episode where all fluffy adjectives disappeared from everyone's writing...only the facts nothing but the facts!

[swebster]

It certainly feels like the Twilight Zone! Except this is the episode where after you fix everything on your MH it starts to run like crap and gets lousy mileage!

Maybe it's not the MH. It could be the mechanic!

Not that I don't aspire to be just like Dennis in everyway possible but if there is one thing I want all to my own it would be to have my old mileage back. Not even going for the "10% - 20%" increase often extoled by those who have added headers. Plus I just don't like changing plugs every 500 miles.

Alan - wanna trade? Think of all that extra room and the rear bedroom and the wrap around windows. My 345 could be the perfect RV for you!