Webers IDA vs IDF

[saltshaker]

I was looking at weber carbs and noticed that there are two different ones, IDA and IDF what's the difference both are down draft? Both are available as 48's and then there was Empi carbs....could someone explain the difference...
Jon

[Gaz64]

Jon,

IDFs are available from 36 - 48mm with the largest available venturi at 40mm. They are more streetable than IDAs with a better overlapping progression circuit, 3 progression holes from factory.

IDAs come out as a 48mm, but can be modified out to 51.5mm. The largest available venturi is 45mm. The are 62mm IDAs available from Gene Berg, EMPI etc.

JayCee enterprises - Â WEBERS BY JAYCEE

The progression circuit can be modified as described in other weber tuning threads.

If you have a choice for manifold, it then comes down to the style of driving you intend on.

The IDA is more cold blooded since it has no cold starting circuit unlike the IDF.

[alkire248]

Jim Inglese is weber guru. Ton of info on his website Home

[nanard289]

Hi Jon
In complement of Gary's explanations, IDA and IDF carbs have a different fixing pattern. IDF body center line is 90mm and the larger IDA is 120mm. It means that they should be installed in a dedicated manifold and there are not switchable. For engines with large displacement using IDA, it is better to add a third progression hole to improve ... engine progressivity. Start with a small drill of 1.2mm and then test it. If it not enough you can enlarge it to 1.5 or 1.8mm.
Sorry for the missing pictures but larger attachements are not possible

[Gaz64]

Originally Posted by nanard289

Hi Jon
In complement of Gary's explanations, IDA and IDF carbs have a different fixing pattern. IDF body center line is 90mm and the larger IDA is 120mm. It means that they should be installed in a dedicated manifold and there are not switchable. For engines with large displacement using IDA, it is better to add a third progression hole to improve ... engine progressivity. Start with a small drill of 1.2mm and then test it. If it not enough you can enlarge it to 1.5 or 1.8mm.
Sorry for the missing pictures but larger attachements are not possible

Yes to all of the above, the IDFs being smaller make the whole package smaller than IDAs.