48 IDA Webers

[Gus Meyjes]

I've been running 48 Ida's for 7 years on my car now. I can't seem to stop them from sweating/leaking. Stains all over my carbs and intake manifold. What do you guys do to prevent that? Or is this something I have to accept as a "normal" Weber thing?  Has anybody rebuilt them with a liquid gasket sealer?
   
   Gus

[Gus Meyjes]

Not really. But thanks
   
   Gus

[B.P.Bird]

Gus,
   They do tend to leak after shut down - percolation. The fuel comes out around the throttle spindles. I would avoid the plastic gasket and suggest you have a careful session setting up float bowl levels. For what it's worth I find that the needle valve on the 48 IDA is the culprit in most flooding problems. I had the same symptoms and cured them immediately with a new set of needle valves. A new set of paper gaskets whilst you are at it would not come amiss and they are quite cheap. Obviously you need the correct fuel pressure, 3.5 psi or so.
   Not sure if you can get Blue Hylomar over there, although there will be an equivalent, this is the old Rolls Royce Aero Engine sealant which is petrol proof, unlike most gasket sealers. Anyway a careful thin smear of this on the paper gasket will eliminate leaks from the joint. Do bear in mind that at full throttle there are no leaks......

[rr64]

quote:Originally posted by B.P.Bird
   
Gus,
   ... For what it's worth I find that the needle valve on the 48 IDA is the culprit in most flooding problems. ......
   

   
   For your amusement.
   
   I had had the occasion to bench tested used 1960s, new old stock 1960s, and 1970s and newer genuine O.E. IDA needle valves. Simple test, invert the assembly (gravity only working on parts), and do a leak down test.  The results were interesting.
   
   Modern (late 1970s to circa 2006 made selection) valves.  So far I have not found a modern one that seals. I tested about six four carburetor systems worth.  I haven't found one that will hold even a couple of inches of water column pressure. I took some to a real nice microscope for examination and found the internal surfaces rough (rough tool marks) and the passage bores exhibited clear evidence that the boring tool chattered and in most cases left the bore slightly oblong.  On the worst one I had to apply approximately 8 pounds in dead weight to make the rubber needle tip conform to the oblong hole. Once I did that it subsequently stuck there. See sketch below.
   
   
   
   1960s parts, even used valves once used on a race Cobra long ago.  Sealed tight every time. In my last test session I applied 20 psig compressed air and let the air pressure 'lift' the needle.  I shut off the air supply and checked leak down. My gage (uncalibrated I am afraid but instructive none the less) showed the pressure bleeding off until a point the needle would not lift any longer. The valves tested stopped bleeding off between roughly 8 and 14 psig. I repeated the test several times dry and several times wet with a light lubricant. Adding a wetting agent didn't significantly change the bleed down results. I examined some of these used and new old stock valves under the microscope also. The bores in the 1960s valves were very smooth walled and the needle contact interfaces appeared very true to the needle tips.
   
   
   My conclusion was that a lot of modern troubles with the IDA series in fuel control is due to the apparent low amount of care taken in the manufacture of the modern needle valves. (Note: I have run up against a few problems like this on needle valves and power valves for modern made Holley brand replacement parts for Ford applications that I have worked on. The issues are frequent enough that every valve gets bench tested prior to final reassembly. I do cull out and discard brand new service parts from time to time.)

[B.P.Bird]

Dan,
   Is there a possibility that we could rescue the situation by some sort of lapping in procedure to seat the valve correctly ?

[rr64]

quote:Originally posted by B.P.Bird
   
Dan,
   Is there a possibility that we could rescue the situation by some sort of lapping in procedure to seat the valve correctly ?
   

   
   Great question. The answer is I don't know. I have studied a "bad one" quite a while as I wonder how I could get it apart and back together. I have not tried one but it has been said that Gene Berg (spelling?) manufactures some really nice valves.

[AC Ace Bristol]

Gus.
   
   The Guys on this side of the Pond who Drag Race their highly tuned Methonal VW Bugs use said Gene Berg components especially in twin 48s and have no leakage problems.
   I will have a word with one or two to see wether they lap the valves or have specific tip..[;)]
   
   Could the  careful use of  a carborumdum stone improve the shape and surface finish of the valve therefore improving the seal surface and  eliminate fuel leakage..[?]
   
   Keith ..[:)]

[Gus Meyjes]

Thanks guys, that was very helpful.
   
    I'm planning a rebuild this winter. I can get Hylomar and was thinking about using it. I was just a little hesitant about gumming up my carbs. I've read about the poor manufacturing of the modern Spanish Webers. Castings being a lot less precise. Not sure there is anything to do about that. Curious to hear from you, Keith, if the VW guys have anything else to offer. I have DCOE's on another car and found that the surfaces were not flat at all, resulting in leaking right past the gasket.
   Frankly, the gasket sets available seem to be of poor quality.
   
   Gus