CIS to carb conversion.
 

Has anyone done this conversion without doing any other mods to the engine. If so, how has the vehicle ran for you and how much fuel economy do I sacrifice from doing this conversion.

Norm:

The net result of how the car will run is directly related to carb configuration, setup and adjustment.

Fuel economy really depends on what your right foot happens to be doing at any given moment,...:) If these cars are jetted and adjusted correctly, the mileage CAN be pretty decent but real-world fuel consumption is all about HOW the car is driven.

dbl webers
 

I put a venom stroked four 2.o in a seventy three 1.7. Got 2.0 jets and it ran rich. So finally went with weber like carbs. It runs reasonable strong but could run even better. Bought a carb vacuum ball set up to adjust carbs. Place a bung in the right exhaust to get air fuel mixture ratios of thirteen to one. I am in the process of taking off the left exhaust and putting another sensor in that bank so I can adjust the carbs equally on both sides. I am buying the air fuel sensors from edelbrock in the summit auto parts at about $129 a piece. Hope that works.

My engine internals are stock, externally I have SSI's and a M&K muffler with 46MM PMO's and she runs fine. I probably could do more tuning to dial it in for a little better mpg but it's not too bad.

I have a bone-stock 2.7L engine with Webers on it and I absolutely love the Webers! Tab Tanner at Autobahn Garage did the work and I bought the Webers from a guy here and all other required parts from Pierce Manifolds (Pelican didn't carry the parts or else I would have gotten them here). My mileage dropped a few MPG, especially in city driving but on the highway I get 20MPG. The sound is fantastic!

carbs
 

Zenith tin carbs are good for only 175 hp. No more cis headaches

c i s carbs in stalled

From a lot of research I've done over whether to entertain going (back) to MFI, vs. CIS vs. some form of EFI on my carbureted 72E...you WILL have a noticeable increase in fuel consumption with carbs, regardless of how carefully tuned. Figure, at best, several mpg worse than the same car with CIS, which will worsen with aggressive driving and any derangement from perfect tuning. Again, I am not the expert, just an amateur meta-analysist...and personally, my car gets horrible mileage, even well-tuned.

But, the look and the sound of the carbs is worth the penalty to me, even with $3 and up gas. As far as how it runs, its great at high rpms; starts harder than a CIS car and idles more poorly. But, the sound...and what a simple, elegant-looking engine bay...