| Author | Message | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1724 Registered: 12-2000 |
True, I can't remember which source stated to measure: "...the nearest part of the float to the cover...". I have the Passini books as well. I didn't quote from it as I can't reach it (buried under piles of rubbish). I understood that there may be discrepencies if measured at the seam (if the flange of the one part could have more of a "flare" to it, than others on the stamping production line, thus it would make it that much larger in dia.). Whatever the case, I doubt that this splitting-of-hairs measurements would have a profound affect on the running of the car. When I popped off the covers for the first time, the floats were WAY off (+/- 5mm), I have no idea how the car ran so smoothly before... You say "toe-MAY-toe", I say "toe-MAH-toe"  | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 129 Registered: 5-2001 |
Thanks Peter, It appears there's a disagreement between our sources. The GT-4 SM, my 78 OM, and John Passini's Weber Carburattors Tuning & Maintenance book, don't specify where on a DCNF float to measure to. My paperback Haynes Manual, Copyright 1986, does not specify in words where to measure to on the floats, for DCNF's, but refers to two pictures that clearly show the measurements being taken, with a dial caliper, to the larger diameter, for both the float droop and closed positions. This Haynes book also discusses float adjustments for the DCOE carbs. For this carb series, a dowel is placed between the float cover with gasket fitted, and the surface of the float (like a round feeler gauge). The book specifically says to file a notch in the dowel to prevent contact with the soldered, central seam. If you reference to the float body, as indicated in Peter's picture, the float and fuel level will be about 1 mm (Peter could you check the difference in heights?) lower than if referenced to the larger diameter. This method will result in a slightly leaner mixture for all conditions, than if referenced to the larger diameter. John Passini states in his book, the closed position should be set with a tolerance of +/- 0.25 mm and droop +/- 1.00 mm. The danger in setting droop is if the float droops too far, the tab depressing the needle valve may go over center and can stick in the full open position. It�s safer to err on the side of not enough droop than too much droop. John also points out it is more important to set the closed heights of all carbs the same than to worry about 0.50 mm in height. So, I guess you pick your method. Just be consistent and tune accordingly. Anyone else have more info or thoughts on this? | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1722 Registered: 12-2000 |
I'm sorry Bill, but both the Haynes manual and Pat Braden's Weber book state to measure at the float body, not the float seam. | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 128 Registered: 5-2001 |
Greg, Your last email to me indicated the problem is not so severe if you apply some choke or if you slowly let out on the clutch with minimal throttle. With minimal throttle, you have good vacuum to draw in the necessary emulsified fuel. Putting on the choke enriches the mixture. You stated both of these actions seem to help your problem. To me, this sounds like your mixture may be a little on the lean side, when backing up a steep grade. This makes sense, when you consider the float chamber is on the side of the carb toward the front of the car. The idling and progression circuit is toward the backside of the car. With the car nose down, the idling/progression circuit is raised relative to the float chamber, and more importantly, the idling/progression circuit is higher relative to the fuel level. This will tend to lean out the mixture. Your car is a '78 like mine. Set your float levels to 48 mm, as Peter shows in his picture, except measure to the larger diameter of the float. The measurement is taken with the float bracket tab just kissing, but not depressing, the spring loaded ball of the needle valve. Carefully bend the tab, and only the tab, contacting the needle valve, as necessary to adjust the float height. I had to remove the pivot pin several times to get the tab bent correctly. Be patient and get it right. Tilt the carb cover until the float hangs at maximum droop. Measure the float height in this position. It should measure 58.5 mm, for a 10.5 mm stroke. Carefully bend the droop tab to adjust as necessary. This droop setting is not as critical as the needle valve closure setting, which controls fuel level. With float levels set, carbs synched, and ignition timing set, you're now in a position to set the idle mixture. | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 127 Registered: 5-2001 |
Peter, My �Weber Carburators Owners Workshop Manual�, shows the measurement to be from the face of the cover to the "soldered on end cap" of the float (i.e. the larger diameter of the float). | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1721 Registered: 12-2000 |
Richelson:  I set mine to 48mm closed, 58.5mm open | ||
| Greg Rodgers (Joechristmas)
Junior Member Username: Joechristmas Post Number: 163 Registered: 3-2001 |
I just finished adjusting the carb floats. 2 of the 4 were in proper adjustment but the other 2 were out. One was at 64mm. It didn't help the reverse problem. If anyone has any ideas please let me know. I am thinking that this must just be the nature of the Webers. Thanks for the input. | ||
| Bob Campen (Bob308gts)
Junior Member Username: Bob308gts Post Number: 82 Registered: 9-2001 |
When I rebuilt my carbs I set them at 58.5 open 50 closed. No two were set alike at teardown. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 614 Registered: 1-2001 |
Richelson -- Just a ruler is all you need to check/set float heights (see Fig. 18, page C20, in the 308GT4 WSM). The adjustment is made by bending the "float tongue" on the float assembly itself that pushes against the needle valve. Refer to your particular year/version OM for the most reliable carb setting data IMO (in the WSM section C it says 48mm, but in section O it lists 50mm). | ||
| Richelson (Richelson)
Member Username: Richelson Post Number: 645 Registered: 12-2001 |
Does anyone know how to adjust the floats? What tool do you use to measure? | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1718 Registered: 12-2000 |
I have had issues with pulling away from a stop sign on a steep hill, the car kinda coughs and sputters a bit until I give it a little more gas, then it clears its throat. I always back into my garage (and where ever I park) and the car does tend to slow down, but it has never stalled on me. The ratio of Reverse gear is nearly identical with First. I'm sure all of this is related to the float-bowl level, its relationship with the emulsion tubes and the velocity of air-flow in the barrels at slow speeds (its effect of drawing fuel from the bowls). If you've set the heights to spec, the mixtures and balance are sync'd and the car drives as it should under normal conditions throughout the rest of the gears and speeds, I wouldn't worry about it too much. The beauty of FI is it can meter fuel flow acurately with barely a trickle of air-flow (hence precise and smooth driving at parking speeds). Carbs are relying on the vacuums induced by the venturi effect to draw fuel out of the bowls: a little bit harder to regulate in the same situation.... | ||
| Greg Rodgers (Joechristmas)
Junior Member Username: Joechristmas Post Number: 160 Registered: 3-2001 |
I was wondering if floats go out of adjustment? I have synced the carbs and my carb 308 runs great with tons of power in all of the forward gears but I am still having the reverse issue. When I go out of my driveway or a steep grade in reverse the car will want to stall and the more gas I give it the more it will want to stall. If I have momentum the car will go up a steep hill just fine. Could it be a float issue or is it just the gearing of reverse on a carb 308? I can go a snails pace and get out just fine with my 308 QV so I am thinking there must be something I am over looking or the gear ratio as the QV is geared lower. Any ideas? |