Webber decision: IDA or IDF?

[renaissance man]

Hey Everyone,

I am replacing my intake; Weiand Stealth 8020, and Carburetor; Holley 650DP, with a new Jim Inglese 4x48 Webber Induction system. I'm trying to decide between the IDA and IDF? I am solely a street driver so I'm leaning a bit toward the IDF? In Central Texas, no need for a choke. This is on my 289 K-code. Currently sitting at 292.868 ci. Running an Isky Racing Cam:
RPM-Range 2000-5500
1.6:1 Rocker Ratio
Grind No./Type 262-Supercam Hydraulic
Low/Mid-Range Performance Cam
9.5:1 Compression
4.10 Axle Ratio

According to Jim Inglese: "The IDF units (top Picture) are both compact and extremely versatile, offering you the choice of 44mm or 48mm carburetors. The smallblock Ford 4x48IDF unit is shown here, as shipped, in standard form with no options. The Weber 48IDF packs the same punch as the 48IDA (Bottom Picture), but in a more "squatty" package. These are excellent for low hood clearance applications."

Thoughts?
[ATTACH][/ATTACH]

[Mark IV]

Give Jim the full specs on your cam, Weber can be fussy about the duration/overlap, it causes reversion (spitting). Jim is the guy for Webers and the IDF are fine for the street.

[1795]

Go with the IDF's. As Rick says above, give Jim your full cam and engine specs specs. I have 48IDA's on the race 289, they love wide open, not so much the putting around paddock stuff. He will want to choke those down to 44mm, let him set them up. 48's are too large for a small block, on my full race engine they are choked down to 44.

Have fun.

Jim

[1985 CCX]

Ditto x 2, above

I run IDA on the street and they are less street and love 100% open.
My friend runs IDF in a FFR Coupe and seems to have more smooth street use than I do.

I always get, that thing runs rough. Its because its not set up for 35mph.
Once they open up its all smiles, just need to live with both sides of the IDA's.

[CompClassics]

I work with Webers regularly on both big block and small block down draft applications as well as other side draft applications. The IDF series are more street friendly as they have a progression circuit that the IDAs do not have. That being said there are modifications, some IDA manufacturers offer them as standard, that help the transition between the idle circuit and the “Go” circuit. There are also manifold modifications that help this also. I prefer the IDA series as that is what the cars were equipped with in period. The nice thing about the IDA series is the fact that they are infinitely tunable and can work on fairly small engines all the way up to big big block engines, you just need a competent Weber tuner. The other thing that complicated any multi-carb installation is the throttle linkage, the throttle linkage is the MOST IMPORTANT piece of the puzzle you can install, especially the rod ends and levers! One cheap sloppy rod end or one lever that doesn’t have the same movement geometries as the rest will destroy and or frustrate an otherwise good installation.