[Earl J]

The only differences between new/modern 48 IDA’s and early that I can see are:
Early EW carbs up to “48 IDA-4” but not including do not have the triangle “V” bosses (for linkage?) on the outside of the bodies. The earlier carbs will also have serial numbers instead of date codes. I will not include the pre-48 IDA carbs known as the IDM which were also 48’s.

Internally, the EW IDA, IDA-1 and IDA-4 have the screw down jet pump nozzles with the check ball in the hold down screws themselves. I may be wrong on the IDA-4 which started production in the late 60’s early 70’s. There was a transition period where minor details changed, most notably the exterior vertical mounting bosses for linkage (I’m guessing) V8 applications don’t use them. All these 48 IDA’s came with two progression holes.

Modern IDA’s the ones from vendors like: EMPI, Redline and others or either cast “made in (blank)”, the ones from Spain, and back to Italy or South America and China (more currently) are pretty much the same design. The details I’ve seen are the push on jet nozzles that take the rubber “o” rings and more currently the 3 progression holes. Machine screws are used (on modern) instead of studs and nuts found on early body and air horn attachment methods. That’s about it.

Construction quality on modern units is an unknown to me. So just be careful and be VERY selective if you’re buying used pieces. (Other people’s frustrations) Also check the number of progression holes between ALL the carbs.

The bad thing about buying used is; I wouldn’t trust the jetting in them as some previous owners modified them (soldered and or drilled out) so what they read may not necessarily be what they are. Just so you know what “stock” 48 IDA’s came jetted brand new out of the box (at least early originals):

37mm venturi
4.5 Aux Venturi
135 Main Jet
F7 E-tube
120 air corrector
120 Idle jet holder
70F10 Idle Jet
50 Pump Jet Nozzle
50 Bypass Jet
25.5 Float
200 Needle Valve

I would talk with Jim Inglese as noted earlier for a base line jetting based on your car specs. Jim will ask. If he does set you up MAKE SURE you ask him what size he drilled or modified a particular jet to. As he will grind off the size leaving you clueless.

Lastly read Tennessee Tim’s Weber Tuning Tutorial posting here on the CC forum. It is one of the most informative writing pieces available anywhere. It’s currently free. It’s better than most books out there.

Have fun.
~Earl J