Fuel supply (injection to carb) ???

i would go with a 600 holly. The efi fuel pump is way to much. A carb only needs 7 psi of fuel pressure. The thing to do about that is pull the tank and remove the fuel pump get a pick up tube for an 85 back car and get a fuel pump and mount it to the frame somewhere next to the gas tank.

I think a 650 carb would be fine, id go with a holley carb, i love my holley AED 750.

im pretty sure your stock fuel pump will have to be changed to either a mechanicial or to a aftermarket fuel pump like a aeromotive. im not sure about the fuel lines i think it would depend on what type of fuel pump you end up going with.

Im pretty sure you would need a adjustable FPR but i could be wrong.

650 will work fine but your going t lose some bottom end.

Run a return style regulator and you should be ok for a while. Sooner or later the pump may die because you are deadheading it against the regulator, but then again I've known people that have run this way for years.

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. Be aware that you are violating several Federal laws concerning the removal of pollution control equipment. If you operate the vehicle on public highways and get caught by the Feds (doubtful, but possible) you could be subject to fines and imprisonment. You won't get any more power from a carb than you will from EFI.

The following information is intended for informational purposes only. Operation of a motor vehicle modified in such as manner as described below should be limited to off road use only.

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 are one of those few people who do excellent work, please disregard my negative comments. They are not intended for you.

Quality, quality, quality…
Some of the motivation of my negative comments about carb to EFI has to do with the quality of electrical workmanship. A lot of the wiring “repairs” that I have seen on the road and in the junkyard looks like road kill. The other part of my negative view stems from people who can’t grasp the operation and tuning of EFI. Carbs have their own set of requirements and some learning is required to get the best performance. Every car is different and each installation needs to be tuned to get the best performance. Putting an “out of the box carb” or one from someone else’s car isn’t the way to success. There is no auto compensation for small variations in carbs like there is for EFI. Just throwing a carb on a car because you won’t bother to learn how EFI works is a poor excuse.

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. If your pressure reducing regulator ever fails, it will dump enough gas down the engine to wash all the lubricant off the cylinder walls and dilute the oil to the point where it no longer lubricates. 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. Do not try to wire the fuel pump without the relay. The 15-20 amps the pump pulls will overload the circuit. This will take power away from other items on the same circuit or cause the fuse or fuse link to blow.



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.

For stainless steel braided hose and fittings for automotive use:

See http://store.summitracing.com/egnse...el+hose&searchinresults=false&N=+115&y=6&x=23

http://www.jegs.com/webapp/wcs/stor...hall&searchTerm=stainless+steel+hose&x=18&y=4

See http://www.aeroquip.com/pages/performance.html for more information on High performance automotive hose products

AN fittings require a 37 degree flaring tool. A standard automotive or household plumbing tool is 45 degrees and cannot be used with AN flare fittings.

See http://www.mscdirect.com/ , http://www.mcmaster.com/ or for the flaring tool you will need . Prices start at $75 and go up

http://www1.mscdirect.com/CGI/N2DRVSH?PACACHE=000000013509163


http://www.mcmaster.com/ctlg/DisplCtlgPage.aspx?ReqTyp=CATALOG&CtlgPgNbr=2252&term=Flaring


While you are at the electrical part, you'll need a Durspark or similar ignition system. The 85 Mustang GT 5 speed has a suitable Duraspark distributor with a steel gear compatible with the roller camshaft. 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.

Tools needed:
Crimp tool for connector pins $9-$30 AutoZone, NAPA, Advance Auto Parts or other store
100-150 watt soldering gun (recommend WELLER 8200PK soldering gun kit 100/140W) $30 at Lowes or $40 at Home Depot
3/32”-1/8” rosin core electrical solder, 1/4 lb roll $6 at Ace Hardware, Home Depot or Lowes
Assorted sizes of heat shrink tubing. Buy long pieces and cut length to fit. It is cheaper that way. http://www.partsexpress.com/webpage.cfm?&WebPage_ID=346&CFID=169547&CFTOKEN=34300345
Hot air gun to shrink the tubing ($30-$40) Home Depot
Jeweler’s screwdriver kit $5 at Ace Hardware
Assorted automotive wire, 18-16 gauge 10’-20’ foot spools in different colors. $5 a roll at Advance Auto Parts.
Ford connector pins AutoZone, NAPA or other store $5-$10 for a kit of 10-12 assorted pins

You will have $110-$150 in materials and tools if you don't already have them.

The water temp and oil pressure signals feed from the sender to the main harness through the 10 pin EFI engine harness. To utilize these senders, you need to identify the wires and find a way to reconnect them to the main harness after the EFI engine harness is removed. You need a weatherproof quick connector to join the sender wiring to the main harness.

You will need to construct a wiring harness from the ‘85 carb distributor to the Duraspark box if you go Duraspark, or other distributor to coil wiring.
The voltmeter picks up its signal from the switched voltage present on the instrument panel, so you don’t need to worry about that.

The fuel tank gauge is also independent of the computer wiring.

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs


How to solder like a pro - http://fordfuelinjection.com/?p=7 a must read for any automotive wiring job.

Soldering pigtails onto existing pins is road kill quality work as far as I am concerned. Take some time to study the way the Ford connectors are assembled and you will find that a small jeweler’s screwdriver will release the pins from the connector shell. New pins and a crimping tool are available from the Standard Motor Parts or Bendix Electrical parts line that the NAPA & Bumper to Bumper Auto Parts stores carry. Ask any auto parts store about Standard Motor Products or Bendix Electrical wiring parts. Those that carry them will be able to get the parts you need. AutoZone has a cheap kit with 10 pins for about $5. Just enough pins to leave you short when assembling a connector.

One of the interesting things about the Ford OEM wiring diagrams is that the connector shape on the drawing matches the connector shape in the car. That makes it easier to identify connectors and circuits. OEM Ford diagrams are available at for an 85 Mustang at http://www.helminc.com/helm/Result....edia=&mscsid=2M838NG3R5SR2MCS00A3HVE05T03C501 or can be found in the Chilton series of auto repair manuals for Mustangs.

The following is an excellent idea from a fellow Stangnetter who tackled the wiring plan the right way. He obtained the wiring diagrams from an 85 carb'd V8 Mustang and laid them out side by side with the diagrams from his car. He then traced out each circuit and the wire colors and connectors associated with them. After tracing the circuit and connectors for a circuit, he laid out the changes he needed to make. One circuit at a time made a difficult big job into many smaller easy to manage jobs.

I picked up an 84 t top notch 4 cyl car that's set up for carb. i'm droppin in the motor outta my 87 an retro fitting a carb set up to it. I'm just going to run the 3 guage auto gage set up so i don't need to tap the wiring harness for those. I think I'm also gonna throw on one of those edelbrock air/fuel guages to keep an eye on rich/lean conditions. I might try to sneak it thru emissions since i'm using cats an it was a carb car before. just lean it out an take the timing way down. any one ever try this?

fabfordtech said:

JRICHKER, I really do appreciate you information all was helpful some less than others but thanks, really good stuff. Few things we need to think about..... First off my engine bay has only master cylinder and solenoid nothin else, previous owner was setting up for drag car so thats why its getting a carb. *Secondly your right carbs dont make more power than EFI but their a whole lot cheaper. To do efi right one needs a standalone system or a very good tune. *Thirdly you mention removing factory electric pump and putting aftermarket pump on it. Why? That makes no sense factory pump only supplies 40 psi aftermarkets are upwards of 60-150, were trying to reduce pressure. *Forthly even EFI motors use pressure regulators and could have the regulator bust and have cylinder walls washed. Im not critizing just commenting. I think Im going to use a return style pressure regulator and install it inline with the factory lines, while ommiting the rail connectors. Oh and steel braided lines arent needed. Why run a line if theres already one there prebent for you. THX CHRIS

Click to expand...

The factory pump will put out 60 PSI or more, but at reduced volume and lifetime. Don't believe me? Crimp the return line on an EFI system and watch the pressure rise way past 40 PSI. The use of a return style regulator is still a band aid approach to get the 6-8 PSI required by most N/A carbs. If the regulator fails, the carb will immediately be flooded with fuel, dumping liquid gasoline into the intake manifold. This would kill the engine, but an electric fuel pump would continue to dump fuel as long as the key was in the Run position.
EFI engine use O2 sensors to detect the air/fuel ratio and can limit the exposure to a failed fuel pump regulator. The engine would not see the sudden dump of fuel into the intake manifold, but an over rich condition that would cause poor performance. When the engine quits turning, the injectors quit squirting. That limits the exposure to a failed regulator.

The 1/4" pressure and 5/16" return lines were not designed to provide the fuel flow volume required for proper operation. High performance carb systems typically use a 3/8" line to assure fuel delivery at low pressure high volume.