I wouldnt do it,but to each his own.well for starters I dont see how you could keep the puter without the EFI,even if u could youd be throwin codes out the wazoo.and if u ditch the computer you would have to rewire the ignition swap out the dizzy,just seems like a lot of work,plus youd never pass emissions.JMHO
Check all the information you'll need for that swap at http://www.jason.fletcher.net/tech/efi-carb/efi-carb.htm. A liitle side note if I may, I've been using a low-pressure in-tank FP for 13 yrs. and no problems so far with mine. The pump is one from a Taurus '88 2.5L CFI, a bypass adjustable regulator and the same OEM fuel lines. Hope this helps.
A repost of some of my previous comments is in order...
A word of warning on EFI to carb swaps: don’t expect to pass emissions in any state that does comprehensive smog inspections, because it won’t happen. You won't get any more power from a carb than you will from EFI.
Doing the swap: You must know how to read electrical diagrams and wire circuits properly to do the swap. Don’t take shortcuts or cut corners in the fabrication of the electrical or mechanical assemblies. If you do NASCAR quality work, the car will look good, run good and be as reliable as a carb’d car can be. Take pride in a job done with excellence.
If you do the hack job that is common among folks who don’t understand electricity or computers and are doing the conversion because it is easier than dealing with the EFI system, the result will look like and run like road kill. Wiring harnesses chopped up and spliced together with electrical tape, loose and dangling hoses, fuel lines spliced together with 3 types of fittings speak of ignorance and sloppy workmanship. If you can't do it right, don't do it at all. I wouldn’t wish a car with that kind of workmanship off on my worst enemy...
Now that the rant is over, here’s some practical advice…
Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.
Do not attempt to leave the EFI in place in an attempt to control either the electric fuel pump or ignition. Doing so qualifies you for the “Road Kill Mechanics Award”.
If you try to use your current tank, you will need to pull the fuel pump out and fabricate a pickup tube & strainer sock to replace the fuel pump. Or you can have a sump fabricated and welded onto you existing tank. Many welding shops will not weld fuel tanks because of the dangers involved if the tank isn't purged properly.
You will need an external electric fuel pump unless you change the timing cover for one with the mechanical fuel pump mount on it. Rip all the EFI wiring out, and the computer controlled fuel pump won't work. You will need to add a relay & switch and wire in the existing inertia switch for an external low pressure electric fuel pump.
You will need to run some new fuel feed lines or braided hose. The 3/8" aluminum tubing works well, but you will need a flaring tool and bending springs to fabricate the lines. Braided hose is easy to run and route, but is much more expensive. It is about $3.50-$4.00 a foot plus the end fittings, which are $3-$4 each. Fabricating hose assembles can be difficult, but anyplace that makes hydraulic hoses can do it for you for an extra charge. See http://www.amazonhose.com for more information.
While you are at the electrical part, you'll need a Durspark or similar ignition system. The EFI ignition depends on the EFI sensors to advance the spark. Rip out the TPS and MAP/Baro sensors and the computer will have no idea of the proper ignition timing for best performance. Running a fixed timing setting is only for test purposes or for a race track only car. Don't try it on the street: the results will not be nearly as good as a properly setup Durspark or equal. Crane makes a really nice distributor for non-EFI applications. . See http://www.cranecams.com/index.php?show=browseParts&lvl=4&prt=127 for more information.
It definatly will be easier to stay with the EFI, But He will need to read and understand schematics of the elctical system, especially if he wishes for gauges and ignition switch to operate correctly, Have to adress the fuel tank and pump, I have used an externakl holley pump with a fabricated in take pickup, new fuel lines, I used a Msd dizzy and there msd 6al box to light the fire, I also used a pressure switch on the oil pressure side to switch the fuel pump on and off, if it sense's oil pressure the pump comes on if not no fuel, Its a nice safety feature, Make sure to gut all of the EFI stuff, a clean engine compartment is a beautiful thing. Good Luck!
i switched to carb just because i had a speed density car that couldnt handle my cammed 331.its not hard to do but unless he is heavily modifiying it, he is wasting his time.....need and fuel tank pickup, electric fuel pump, new fuel lines, ignition, distributer, carb of course, intake
wait i just saw that your buddy is speed density too....if he is going to go deep into modifying throw a carb on and it will be cheaper than a maf conversion with a decent intake
either do it right, or don't waste your money............I have always said that
I will be converting mine come next fall, after my body is completey restored back to brand new. And will be replacing all guaging with Autometer Electric guages