Weber 44 IDFs on KMS 289 car
 

I'm thinking about converting my KMS 289 car (what they call a 'hybrid' with 427 frame but 289 slabside body) from a single four-barrel (ProForm) to Weber 44 IDFs. This is a rather mild engine and runs well, but I think the throttle response would be better with the Webers.

Has anyone done this and what sort of problems, if any, have you run into? I've written to KMS asking if they have the linkage as something I can buy, or will we have to fabricate it. Also I know the Webers like low fuel pressure, like 3-4 pounds, so we'll have to install a regulator and gauge for that. KMS cars of that era came with a Holley red pump which is about 7 pounds, IIRC, which will need to be reduced.

Also, if anyone has had a particularly good experience with any Weber shop I'd like to know of it- right now we're looking at Top End Performance, who were very helpful by phone.

Finally, years ago, I bought a 4x2 Weber rig, which it turns out is 48IDF carbs, which are too big for my engine. This has never had fuel in it. I plan to sell that setup, I'll photograph it and post it here. Thanks to all, in advance, for any advice.

I used Jim Inglese for my 289, if these guys are close to you and you feel comfortable, I know nothing of them so cannot comment. They seem to have some good information on their website. Pierce Manifold is in CA as well, I have purchased parts from them. I would suggest that prior to purchasing any Webers that you talk to whoever you may be purchasing from and discuss your current engine specs, inclusive of cam, heads, cubic inches, stroke, compression ratio, HP and desired performance. The carbs need to be tuned to your specific engine, you cannot buy off the shelf Webers and just throw them on a car and expect it to work right. They need to be tuned to the engine, and anybody worth their salt that is selling them to you should be able to do that for you prior to shipping.

Once setup, Webers really need any adjustment, unless you are changing altitude greatly. Jets/air correctors, etc., are easy to change. The linkage an be a pain to get right so that all four carbs are acting together. You need to carefully make sure that there is no binding and pay close attention to the bracket on the head that connects the linkage between the carbs to the throttle pedal to make sure that it is not flexing.

Yes, Webers, especially in a street application want between 3-3.5 psi, unless you are racing you do not want to get up to 4 psi. Your gas mileage will suffer, as Webers are not progressive; it is all eight barrels in all the time.

There is the possibility of tuning the existing ones that you have down. I have 48 IDA's on my 289 race engine with 42 chokes in them.

Good luck, and with some due diligence you should be able to put together something that will work. Just be aware that your cam may need to be replaced depending on the cam specs. Webers can handle a little reversion, but do not like a lot of it. If there is too much overlap it may be problematic in a street application. Make sure you provide your cam card specs to whoever you are purchasing from.

Jim

perfect summary by Jim according to the IDA48,

90% of the Weber carburated small block Cobras are running 48IDA Webers.
That is because the owners want to replicate the glory age of Cobra racing, or because they should because of actually homologating these cars.

48 IDA is a binary race tool which works best with ON or OFF
tuning them for the street is quite a challenge, you have to add a third or fourth idle drill hole and tune it very carefully to a milder race cam, which means about 10%-15% less hp

44 IDF is not a challenge like that, I know some guys riding them on the street with double mpg that I have with my 48 IDA

Good to know. This car does not go to the track except perhaps as a spectator. I don't have those kind of driving chops. It's a fairly mild engine and cam so the overlap should not be a problem. IDF 44s should be adequate.

Now to figure out the best place to sell my chromed 48 IDF rig...

I ditto Jim's take!
Webers are great, I run them, they will bring a punch to the party for sure.
Downside is they add volume to sound and they can be finiky with filters as they are restricted with filters.
I run them no filters which limits you to paved streets as I always avoid dirt roads etc...

My choice is Jim I will have the best package but I do like Peirce for all their parts etc.