MSefi.com read only forum (Jan.15,2018)

...NOT swapping from a carb to TBI, but modifying a carb so that it becomes a TBI

Now, with that out of the way, let me say up front that I KNOW I'll likely be compromising overall performance. But here are my reasons and goals: I have a classic Mustang that is being setup to look old school. Specifically, I always loved the look of dual four barrel carbs. I've thought about simply using dual GM TBIs (others have already blazed this trail) but anyone with any car knowledge can pick them off at first glance and I'm wanting complete stealth for my efi. Sooo, here's my idea (you tell me if there's any hope)....

I'm thinking to block off the secondaries on a pair of Carter AFBs (removing the throttle plates and the top air valve) and afixing a pair of injectors in their place. Because I'll be running two of these "carbs" I'd have the combined cfm of the pimary bores of both carbs so airflow won't be a problem.

Doable? If so, any tips on the best way to angle/direct the injectors. My assumption is that I'll want to direct them as near as possible toward the airflow as it exits the primary throttle plate. Any other thoughts are more than welcome.

Thanks in advance

Certainly doable I would think. But a lot of work. I would start off doing some measurements and study of other Tb's.

A number of issues come to mind (both pro and con) but are way too much for a simple post here IMO.

I would be glad to get some measurements off my 4 Bbl Holley unit if you think you could us them.

Ken

Thanks for the response. The manifold I'm using can't fit Holleys end to end so I'll be using Carters/Edelbrocks. Would you mind listing some of the "issues" that you're thinking of.

The problems you might run into is not having a throttle position sensor. But you could retrofit one to work or base your acceleration enrichment all off of the map sensor but I don't know if that'll work too well. You would have to run a fast idle valve also unless somehow you could get the choke to still work during warmup.Going for the old school look would make it hard to hide sensor too.

Thanks for your thoughts. I'll be using a tps but had thought mount it remotely, perhaps under the dash attached to my gas pedal. I'm also imagining that I can (mostly) "hide" a fast idle valve.

Anyway, I have acquired a GM tbi to study. I could possibly affix the entire injector assembly from these to the top of my Carbs and they should hide under the air cleaners. Alternatively it looks like I can fit the injectors down inside the secondary barrels (replacing the secondary plates), spraying just behind the primary throttle plates. But I have read that having the injectors above the throttle plate is "better". Could someone please give me a technical explanation as to why this is would be the case?