We've proven in past tech articles that bigger isn't always better with regard to carburetor sizing, so be sure to check with the carb company concerning your application and intended usage before choosing. Selecting a carb that's too big is the single biggest mistake that people make. It's always better to have a carb that's slightly undersized, as it will increase throttle response and torque over a carb that is too big. Most 11- and 12-second Mustangs will do well with a 600-700 cfm carb, despite what your buddy thinks. Save the 850 for your 700hp race engine.
Igniting the gas of the carbureted engine requires some different components as well. Early Fox-body Mustangs used the Ford DuraSpark distributor, which was available on many late-model carbureted Ford V-8s. It has a simple three-wire hookup, but according to our own Yo, Ken columnist, Ken Miele, they may not be the best or most dependable setup to use.
"You can go to the junkyard and get a DuraSpark unit and ignition module for about $150, but you have no idea what you're getting," Miele says. Said distributors may have untold amounts of mileage and therefore wear, and oftentimes it's hard to find the associated DuraSpark ignition box you need to go with it.
Even if you find the DuraSpark ignition module, it may not be the best choice for a performance application. HP Performance's Tony Gonyon says, "The Ford ignition modules were known to go bad quite often, and there's more wiring involved than if you use something like an MSD box. Also, the dwell goes away at 5,000 rpm on the stock ignition module, so you're going to lose power."
If you're set on using the DuraSpark distributor, try to get a unit from the '83-'85 Mustangs, as Gonyon says the mechanical advance in these is better, and the '85 units already have the steel gear for use with hydraulic roller cams, if that's the direction you are headed. You should also consider complementing the DuraSpark with a capacitive discharge ignition box such as those from MSD or Crane. As with most projects, yours will likely get faster as time passes, and supplying it with a healthy ignition system from the get-go will be one less headache down the road. There are, however, a lot of good aftermarket distributors, and some that don't even require an ignition box. These work well with normally aspirated applications, but you may want to step up to a distributor/ignition box combo when using power adders.
The last part of the ignition equation is the coil or coil packs, depending upon application. Late-model EFI coils will work with your carbur-eted setup and offer plenty of power for the average performance street machine. They require a two-wire hookup, just like older and most aftermarket coils.
If you've read this far into the article, then you're pretty serious about going to carburetion, however, as easy as the swap may sound, you'll want to consider several things. While most people believe carbureted fuel systems are far more inexpensive than fuel injection systems, this is not always the case, especially if you're starting with an EFI car.
The price of intake manifolds is reasonable compared to EFI units, but throw in quality fuel pumps and carburetors and you can easily tack on another $400-500. A braided stainless steel fuel line is not cheap at $8-$10 per foot (depending on size), and you can sink a lot of money really quickly into aluminum fittings.
For a real-world experience in switching from EFI to carburetion, we spoke with Al Papitto of Boss 330 Racing, who recently switched to carburetion on his high-rpm modular engine. Papitto uses a Barry Grant Race Demon carburetor and Kris Starnes-modified Sullivan intake manifold, along with an Electromotive crank trigger ignition. "I was at the racetrack and saw these Comp Eliminator guys with carburetors who were running fast and never had any problems," he says. "Over the past couple of years, I've hurt the motor with EFI-related issues and grew tired of it."