48 IDA Float Settings

[jhirasak]

I recently decided to check my fuel levels in the bowls since I still had some slight coughs and exhaust pops during the slow speed and cruise RPM range. Typically, when a Weber spits back it is an indication that the AFR is slightly too lean while a pop out of the exhaust indicates that the AFR is slightly too rich. Since the size of all of the jets were the same in each carb, it made me wonder if my fuel levels were the same on all of the carbs. To check this, I purchase a sight glass gage from Bieker Engineering who produces a very high quality product (however it is quite expensive). Upon taking measurements of the current fuel levels, I found a +/- 4mm variation from the average fuel level.

It seems that my initial static float level settings were inaccurate when I first set them up. When I measured the distance (24.2mm) from the top of each carb body to the float tang, I did not take into consideration where the needle seat should contact the tang.

To correct the individual fuel levels in each carb by using the sight glass gage, I built a tool from a long piece of 1/4 in. steel rod by cutting a small notch at one end with a die grinder and thin cutting disc (see attached photo). By using this homemade tool, I was able to adjust each float tang so that the final fuel levels were within 1mm of each other. This seems to have gotten rid of those irritating coughs and pops in the low speed and cruise conditions. I would recommend this procedure for anyone with 48IDAs that has minor hickups under low speed and cruise conditions

As a double check, I plan to reinstall my wideband O2 sensor and check my AFR over the entire operating range.

An alternate method to check the fuel level in each carb is to use static fuel level measurements instead of a sight glass gage (it is also a lot less expensive). To do this,is shut the engine down after it has been idling for a while on a flat floor and remove each of the carb bowl tops to measure the distance from the carb body top to the level of the fuel in each bowl. The advantage of the sight glass method is that it allows you to observe the fuel level while the engine is operating.

I would be very interested to know if another owner of a 48 IDA Weber equipped vehicle encountered the slight miss-fire symptoms that were similar to mine and found the cause to be due to variations in the fuel levels in the carbs.

[PaulProe]

I had a similar problem with my car when I set it up. I think the dry method of setting floats can only be used as a starting point. I found mine to vary a similar amount. Like you, I took the covers off and tweaked the levels to where they were all the same. Made a similar tool as what you have.

I check levels by using a visual gauge that inserts into the main jet well. I remove the main jet, and insert the plastic gauge which will turn dark on the end when it contacts the fuel level. I then can measure the amount between the gauge stop and the end to determine fuel level below the jet well. On the 48IDA, this dimension should be 43mm +/- 1mm

Fuel level is critical in that it determines how the holes function in the E-Tubes - at which point does the fuel flow or emulsify.

Paul

[*13*]

It also matters that the check valves, which the floats operate, are each exactly the right height, or your float height is useless. I just reset mine from 6.0 to 5.5. It did cure my leak down. However, the transition problem which had developed was due to sticky ball valves in the jets below the floats.

[Rick Parker]

Hyde the "Ball Valves" below the floats only control the amount of fuel emited from the accelerator pump squirters. They have no influece on the emulsion tubes etc, they do however create a "Band Aid" and enrich the immediate fuel mixture when the throttles are cracked. They are fully submerged regardless of the float level.


Paul : Interesting way to verify fuel level, cudos to you! This could also be done without removing the Carburetor top, by adjusing dimensions?

[*13*]

The stuck balls don't impede the flow of the nozzles? I've never had this problem until recently. No matter where the floats were set(5.5 or 6.0). I pulled all 4 of the ball valves & the were all sticking. Cleaned them, re installed & all of a sudden, when I give it a little gas, it responds.

[PaulProe]

Originally Posted by Rick Parker

Paul : Interesting way to verify fuel level, cudos to you! This could also be done without removing the Carburetor top, by adjusing dimensions?

Rick
The dimension and tool is designed to work without pulling the top, you just have to take off the jet screen cover and remove one of the main jets. The measurement is from the floor of the jet access well to the fuel level. If you need to adjust the level, then you have to pull the cover. But it gives you an amount you have to raise or lower the level

I specifically like this for my car with canted carburetors. It is important the fuel level in the jet cavity be at the correct height and this automatically compensates for the canted carburetor. Setting fuel level dry per the weber manual does not - you need to change it by 2mm.

I've toyed with working on an external adjustment for the float, but it probably would be a labor of love. Once the float level is set, unless you have a catastrophic problem, there isn't a reason to change it.

Paul

[jhirasak]

There is another method to measure the fuel levels in the bowls that was briefly described in the Weber Shop Manual. This method is similar to that used by Paul. The screen covering the jets were removed and the emulsion tube was also removed. Then, by using a vernier caliper as a depth gage, one should hold the base of the caliper on the flange exposed after removal of the screen and extend the depth gage until it just contacted the fuel level in the well. By taking measurement on all four carbs, one could determine which floats had to be adjusted and by how much. However, the Weber Shop Manual did not indicate what the measurement should be for the desired fuel level in the bowl. Does anyone what this distance should be for the top of the float to be set to 5.5mm above the bowl mating surface?

Perhaps it is more important that the fuel levels in the bowls be the same amount in each carb rather than a specific numerical value.

John

[PaulProe]

John
using the caliper is the same as using the optical gauge. both react when they touch the fuel - the optical gauge changes color - the caliper shows slight movement of the fuel level as the surface tension changes and wraps to the caliper point.

In both cases, the magical number for 48IDA's is 43mm from the floor of the emulsion tube/jet well (the area covered by the screen) to the fuel level.

I've verified this number by using fuel to float the float to the 5.75mm level then replacing the cover & gasket and measuring. I did the test repeatedly to confirm the results. I then also did measurements using an AutoCAD layout and it verified this dimension also. Dean Lampe (who used to be active on this forum with his Webers) learned of this also from an old time Weber mechanic.

I also used the caliper method however it is difficult to find a caliper that has a small slide extension. The cheaper ones are almost the same width as the tube well and very difficult to use.

I've sent you a PM also

Paul

[Rick Parker]

Paul: Excuse me I thought it was being measured with the carburetor top off, my oversight.

On the 48IDA, this dimension should be 43mm +/- 1mm

Does this also hold true for non Canted carbs as on SB?

[PaulProe]

Originally Posted by Rick Parker

Does this also hold true for non Canted carbs as on SB?

Rick
The 43mm comes from the vertically mounted carb/float setting. When you cant the carbs on a big block, you have to raise the fuel level 2mm to keep the 43mm in the emulsion tube well. With a canted carb, if you don't raise the level, the fuel level will be low and will affect the transition process.

The idea is to keep the fuel level at the design height inside the emulsion tube well where the level interacts with the holes in the e-tube and the venturi exit port.

Paul

[Rick Parker]

I havent seen these for 48 IDAs, but if there were copper or aluminum washers of specific various thickness's the float level could be adjusted without bending the tang on the float, and could be more precisely adjusted.

[Cornercarverfan]

Good day all,

I’m bringing this thread back from the dead. The last post above, was posted nearly five years ago by my now late Father, Rick. I now have possession of his 289 Cobra and have spent far too long getting it back in fighting condition. I have spent approximately 4 weeks fighting this car to get it to fire. 3 years of stale ethanol-laden gasoline did a number on the Webers he describes above. I’ve been working closely with Mike from Pierce Manifolds in Gilroy, CA to get everything fully cleaned and dialed. According to what I read above, it sounds like I have some micro tuning to do with relation to the float heights. I have the floats currently sitting at 6mm but have not measured fuel levels in the bowls. I’m 1.5-2 turns out on the idle mixture screws and getting carb backfires on most, if not all cylinders.

Once I have those equal across all four bowls I’ll move onto the ignition gremlins I’m fighting. Thank you to all of you who have contributed to this and other threads. This has been and continues to be one of the friendliest car forums I have come across.

Justin

[*13*]

So good to hear you are working the car back to life. I’m pretty sure he would have had everything set up. He wasn’t running ethanol free gasoline? I’m sure he didn’t expect it would be sitting for any length of time... with Webers, you’ll likely need to get fuel back into the carbs before it’ll run. Did he have it set up with a mechanical or electric fuel pump? Pull the distributor cap, make sure it all looks clean in there & get fuel pumped into those carbs. It depends on a lot of factors but, my idle screws are just over 1 turn out. You’ll need to set this when the motor & oil are at running temp. This may take a good 15+ minutes of driving. If you have the idle set somewhat close, it should give signs of life with a pump of fuel then ignition.

[Ron Scarboro]

General rule of thumb is 3/4 turn out. More than 1 and your jetting is wrong.

Good sources

https://www.jiminglese.com/weber-tech
Tuning Webers

[Cornercarverfan]

Thank you for the kind words and the links, I'll review those in a bit.

The Webers have been completely dismantled and cleaned, it was a necessity. Too much fuel varnish to trust it otherwise. The third progression hole has been drilled and new Nitrophyl floats are now installed. I was the last to drive the car in May of 2015, so I KNOW it runs. My problem is putting the pieces of the puzzle back together correctly. I have spark, I have fuel, but timing is my main issue at the moment. I have NOT removed the distributor from the car, however, have replaced with a like Accel cap and rotor, new plugs (which are now badly carbon fouled) and a new identical coil. The car has an original Boss 302 distributor with the cable drive tach and when I try to line up #1 on the cap, I'm stretching the drive cable badly. I think the original orientation put the wires "back one spot" in the rotation, not that this matters - as long as #1 is at TDC and the rotor is directly underneath the corresponding terminal on the cap.

How does a MSD 6AL box affect timing at idle? It's my understanding there is a flurry of ignition sparks to ensure a complete burn until 3000 or so RPM. My timing light went nuts when I tried to verify spark on cylinder 1. Keep in mind the car is not firing, it cranks, backfires out of the carb, smells of burned fuel. Hasn't run whatsoever since the carbs were removed form the car about 3 months ago.

Thoughts?

[Karl Bebout]

Mystery how the engine got out of time, just from changing the distributor cap, IF the plug wires were put back on the same terminals they came from. Without pulling a valve cover, you can get a good idea of TDC by feeling the compression stroke through the spark plug hole. When you feel the compression and your timing mark is close to TDC, the rotor should be pointing at the #1 cap terminal. See what you have. At least this should give you a starting point.

[Cornercarverfan]

Whatever is going on with this car is truly a mystery. I went to the trouble to pull valve covers to verify timing order. I verified I have an early model 1-5-4 order. I think I need to set the plug wires back one post to get closer to 0 advance. Knowing which wire was #1, I believe I traced form the cylinder head, pulled from the old cap an dropped into the marked #1 spot on the new cap. My guess is everything was scaled back one post on the cap to allow the tach drive cable to reach and not be overstretched. All things equal, retarded will pop through the exhaust and advanced will pop through the carbs, correct? I'm getting there, but now I'm going to need to remeasure the fuel levels with a greater degree of accuracy than the stamped steel float gauge. At least I know what I'm doing this weekend

Originally Posted by Karl Bebout

Mystery how the engine got out of time, just from changing the distributor cap, IF the plug wires were put back on the same terminals they came from. Without pulling a valve cover, you can get a good idea of TDC by feeling the compression stroke through the spark plug hole. When you feel the compression and your timing mark is close to TDC, the rotor should be pointing at the #1 cap terminal. See what you have. At least this should give you a starting point.

[Ron Scarboro]

I don’t think float levels would keep it from cranking. When my float stuck the butterfly was wet. If the top of the butterfly’s is dry and the accel pumps are working (easy to verify visually). Generally, as long as the carbs are in the ballpark it’ll crank, but may not continue to idle beyond a few seconds.

It almost sounds to me like you’re 180 deg out on timing or the MSD is bad. I have a MSD and I can time it off a light w/o issue.

[Gaz64]

180 out would have it backfiring out the carbs.

Static timing should be set around 10-12 BTDC, not at TDC, to get it to start.

Find TDC on number 1, then turn it back to 20, then forward to 10-12.

Gary

[Cornercarverfan]

Thank you @Gaz64 (Gary), I'm used to EFI which makes tuning far easier in my opinion. To clarify for my simple brain, balancer will be set at 10-12 BDC, rotor directly under plug wire one and tune from there? Appreciate all the
help! I'll give this and all the earlier recommendations tomorrow. Neighbors are going to love me

Originally Posted by Gaz64

180 out would have it backfiring out the carbs.

Static timing should be set around 10-12 BTDC, not at TDC, to get it to start.

Find TDC on number 1, then turn it back to 20, then forward to 10-12.

Gary