I want to build a 82mm x 90.5 engine with some nice heads for a daily driver. I am looking for carbs that match a setup like that. I heard too many different things about the different types. I was told that 42 DCNF are the best choice. Is that true? What about IDFs, IDAs and the Dellortos compared to the DCNFs and about their HP gain? Thanks a lot, Alex Alex

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Re: Help on carburation needed (Eric) (21-Apr-2000 20:14:10) Re: Re: Help on carburation needed (Jon) (22-Apr-2000 00:18:23) Re: other options... (Matt Davis) (21-Apr-2000 21:43:52) Re: Your best bet is to use NEW 44 IDF's and learn how to determine what jetting your engine wants (Jim Ratto DRG) (22-Apr-2000 20:20:42) Re: BTW: DCNF's have their floats oriented in the wrong position on a VW...so don't take any corners. Most DCNF guys smile when they ditch them and go to IDFs. (Jim Ratto DRG) (22-Apr-2000 20:29:58) Same experience... (Jason M.) (23-Apr-2000 03:18:07)


You cannot go wrong with the 44 IDF Webers. One thing though..you MUST check the flaot level in them when you buy them. The last 6 sets I have checked have been way too high and will flood when going over hills or rough terrain if not reset. The only problem I have ever had with the 44 idf's has been idle jets plugging. which is simple to cure because they are accessible from the outside of the carb.

Good luck,




what is the correct float setting for a 40 IDF?



Re: other options... Friday, 21-Apr-2000 21:43:52 writes: Eric is exactly right about the 44idf's. Depending on what size cam and heads you are using you should also consider 40idf's. I have used both with great sucsess in large cc daily driven motors. Dellorto in either of those sizes would work well too. Good luck! Matt Davis


Re: Your best bet is to use NEW 44 IDF's and learn how to determine what jetting your engine wants Saturday, 22-Apr-2000 20:20:42 writes: I would say that if you had a choice, to turn to the Weber 44 IDF's. The 40 IDF's will limit your engine's output. I feel most high perf larger cc engines can use a set of 44IDF's, with the stock 36mm venturies. I have installed and tested them even on a 90.5 x 69, 7.5:1, Engle 120 motor in a street car and it ran great. By choosing 40IDF's, you're limitlng the cam overlap and headwork choices you have. I am in the midst of trying to convince one of my personal customers (building him a 90.5 x 84 street motor) into stepping up to 44IDFs instead of his current 40IDFs. His combination of heads and camshaft would work much better if he'd listen to me, but he also didn't take my advice to run 94's instead of the 90.5's he bought. There is a formula I use to determine throttle bore size and venturi size for particular engines. Email me if you want it. have fun, Jim Ratto DRG


a few years back, I spent the day talking to a guy that autocrossed his street car. he made the mistake of running the Maserati Weber DCNFs on his VW and could never run competively because the car would severely miss coming out of corners. He tried different float settings to no avail. This was a 2110 with 42DCNFs, and he later swapped to 48IDAs and came close to winning his class that season. He did notice he was getting fewer races on his Yokohamas though.

The DCNFs were designed to run on Ferrari V6's and Ferrari V-12's and also on Maserati V8s and V6s (a la Citroen SM and Maserati Bora/Merak). In these applications, the float shaft's axis was in the same orientation as the car's axles. On a VW they are set up parallel to the mainshaft of the trans/crankshaft.....wrong for smooth operation.

Jim Ratto DRG


I have a set of 40 DCNF's that I run on my fastback since they fit under the decklid. Whenever I get on a interstate circle onramp the engine misses and stumbles, obviously due to the float position required in a VW that Jim explained. Other than that they run great.

Jason M.

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