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Mon May 07, 2007 9:20 pm

I have a recently acquired sandrail with a 2275 running a single Weber IDF w/32mm venturis. It's woefully under carbed I think. I'd like to get a second carb to build to match the one I have for a dual setup. How can I tell if it's a 40, 44, 48? My Weber books says there should be I.D. numbers below the fuel inlet, but this carb has nothing stamped there. Is this an HPMX in disguise? The accel pump cover says Weber and that's about all.

Mon May 07, 2007 9:54 pm

Look at the base of the carb near the studs.

Mon May 07, 2007 10:09 pm

MURZI wrote: Look at the base of the carb near the studs.

Thanks for that. I had a look, it's still on the car so it's diffcult to make out, but on the back edge of the flange it says IDF 61. And there is indeed a Weber logo cast into the body on the back.

61? I've only heard of 40, 44 and 48.

Scratch that, I didn't see the picture you posted. Where your 44 is stamped looks like crap on mine. Ill have to get it off of the car.

Mon May 07, 2007 10:12 pm

look again ...you did not see all the numbers. I bet it is a 44. Definitely not a 48 as they don't make 32 vents for a 48.

Tue May 08, 2007 9:55 am

If all else fails, you can always measure the diameter of the throttle plate in mm.

Tue May 08, 2007 12:43 pm

The carb is definately an IDF 44. Thanks for the help.

I'm wondering now if it's possible with the right venturi and jet/tube combo to make one of these flow enough to make a 2275 happy?

Tue May 08, 2007 1:03 pm

I would look for another 44 idf and some manifolds. It will run so much better

Tue May 08, 2007 2:34 pm

MURZI wrote: I would look for another 44 idf and some manifolds. It will run so much better
Agreed. Also gas mileage will be much better with dual IDFs than with a single center mount IDF.

Thu May 24, 2007 6:10 pm

:D Ok so I've gotten a hold of pair of IDF 44's and the required linkage, manifolds etc. They have 36mm venturis, 120 main jets, F11 emulsion tubes and 175 air correction jets at the moment. They came from a road going 1775 and apparently were "too much carb". I'm guessing the venturi's may be a little big for my 2275. It's mostly run at a few hundred feet above sea level.

I'm a Weber IDF and VW rookie here, so I'm looking for some advice on a good starting point combo of jets etc. Then I can fine tune it from there.

Also, they are Spain made carbs. Good/bad/whatever?

Thu May 24, 2007 6:50 pm

The carb and vent size you need is dependent on more than displacement. What cam and heads the engine has are big factors here too, to size it correctly.

But for argument's sake, if I had an engine that was made to pull low, and didn't make much power past 5K, then I would use around a 36 venturi. If the engine is to run and make power until 6500, then about a 40mm vent makes sense.

Jetting: 52-55 idle jet, 52 probably good for you at 2000 feet. 140 main jets, 200 air jets on 36 vents with F11 emulsion tubes.

Floats are the MOST important part of proper carb setup, besides good state of health on the engine. Valves, ignition, etc. If you don't do the floats right, you're pissin' in the wind. Just get that right for sure first, the rest will fall into place unless there is something WRONG with the carbs.

Thu May 24, 2007 8:23 pm

mharney wrote: The carb and vent size you need is dependent on more than displacement. What cam and heads the engine has are big factors here too, to size it correctly.

But for argument's sake, if I had an engine that was made to pull low, and didn't make much power past 5K, then I would use around a 36 venturi. If the engine is to run and make power until 6500, then about a 40mm vent makes sense.

Jetting: 52-55 idle jet, 52 probably good for you at 2000 feet. 140 main jets, 200 air jets on 36 vents with F11 emulsion tubes.

Floats are the MOST important part of proper carb setup, besides good state of health on the engine. Valves, ignition, etc. If you don't do the floats right, you're pissin' in the wind. Just get that right for sure first, the rest will fall into place unless there is something WRONG with the carbs.

Good points all. I'll make sure the floats are right when I dig into them. Here's what I know: the heads are "big valve" at least 40mm or 41mm, not sure where actual diameter measurement comes from. I had them off to replace the push rod tubes and verify the bore. The brand escapes me now, but I think they said CB performance. There is a 401 cast on the outside. A couple of the combustion chambers had some signs of pre ignition.

The cam? Not sure, but the previous owner said it was a "couple of steps up" from stock. Of course he said several things that are now in question. I've forgotten the cam number he mentioned. He claimed it was built to handle a turbo some day. My VW turbo expert friend said that cam would not be up to it.

My target operating elevation is more like 500 feet, not 2000. The dunes in Imperial Valley CA is the most frequent destination. With that in mind, I'd say I'm looking for performance in the mid range. Not a super rever but I don't need the hole-shot torque either.

I've had it out once and it was pinging under load on hill climbs. Otherwise it ran well with the single carb but just seemed to go flat after a certain high RPM (no tach right now)

One other thing, one carb has one barrel with the top of the aux venturi all dinged up. Kind of like someone went at it with a hammer. Major problem? Replace it or can I just smooth out the edges?

Thu May 24, 2007 8:28 pm

If there is material missing, or you can't make it perfectly round again without bell shaping it or something, you should replace it.

It was probably pinging due to timing and/or lean condition.. 120 mains on 36 vents is skinny - real skinny.

Stick with the mains and try a 55 idle then.. that should wake it up.

Ah.. did I mention floats? ;)