Hi guys, I have searched and searched with no luck (unless I'm looking in the wrong places.) Has anyone actually fitted and run 48 IDF Webers on the street successfully? I don't want to know about IDA's. Just 48 IDF's. My specific questions are: What actual power did they make, including head type and cam size. Did you run air cleaners, screens or just ram tubes? Did your setup fit under the lid? Any specially big problems encountered.

I know some if of these questions have been answered individually many times previously, but I want to know of a finished, running, driving, system and it's specs. Thanks in advance. New owner of 5850.


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Last edited by gt-pilot
Original Post

I have run 48IDF's on the 302 in my Autokraft Cobra since 1992. Great and smooth with no problems. Stock 9.0 to 1 compression, Ford Motorsport GT-40 aluminum heads, B303 Camshaft. Produces about 350 BHP, dead smooth idle easy starting hot or cold. I can give you all the jetting specs. Run 40mm chokes. I realize this is not for a 351 Cleveland, but you can make these carbs work better on the street than the IDA's due to the IDF having a better transition system from the idles to the mains. This is the key on street driving.

Hi DWR46, thanks for the reply. I have been told they are not big enough for a healthy 351. eg. 6,500/7,000 rpm 500hp. I've had a set on a 351c but it had a very small cam and was only revved to 5,000 rpm.

GT-Pilot: You have a point. We run IDA's on our 289 Cobra vintage race cars and usually use 42mm chokes. I have dynoed a set with handmade 45mm chokes on the 289, and they do produce more power, but the overall area "under the curve" was not appreciably better. We build our motors for a very flat torque curve and do not use lots of revs, as in vintage racing, you need the torque to pull you off the corners. I would think you could experiment with 42-45 chokes on the IDF's. The Weber factory calculation for single barrel per cylinder choke sizes result using 351 cu. in. in a 43mm choke for a 6,500 rpm power peak and a 45mm choke for a 7,000 rpm power peak. You could probably make a set of 48 IDF's work with these combinations.

Last edited by DWR46

DWR46, here's the issue and partly why I asked the question. 48IDF's have a maximum choke size of 40mm. The outside dia is 45.85mm, let's call it 46mm. So the wall is 3mm thick. You could machine the chokes 2mm to 42mm leaving a wall thickness of 2mm. But then it's not going to have much of a venturi effect. Now may be the booster venturi on the IDF is better flowing than an IDA so you have a bit better flow there. But it all seems a bit smallish!! Hence my original questions. There are a few manifolds made or have been made for IDF's, so that makes me think may be they work. But like I keep saying show me the evidence! Cheers

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