EFI to Carb trade off

he's probably getting abit more out of it than you, but in the long run he'll have a bunch more headaches . my suggestion: take the carb setup and try to get some cash from him too, but if you're unsuccessful, no big deal, you'll still have the better setup

Well your old setup is worth more, a edelbrock carb and intake is like 450 but the edelbrock carb is just okay it will make a little more power but not like you really can with a carb the edelbrock carb is good for week end cruses and occasional daily driving but you will have better throttle responce with the fuel injection. And you will think that you lost performance and drivability Personally I would get either a barry grant or holley hp series or even a quick fuel carb the they are 10x better and if tuned properlly better throttle responce than efi the whole metering rod thing sucks .

Yes i would say your efi stuff is worth more. That being said if you are getting everything you want then i guess its a good deal. Just because i want to know why are you going to carb if you have already modded you EFI set up?

Swapping a carb for EFI on a 2000 model car will make the car almost impossible to resell. Your EFI is worth far more than a carb.

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 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. 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 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.

fastangboi said:

no im doing this on my 89gt. and its a pitb to tune the EFI without a programer. also i think its easier to upgrade a carb set up as opposed to an EFI

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Your EFI combo:
for my 80mm cia under hood
76mm C&L maf
70mm t/b
light port match job on HO manifold
1" phenolic spacer
24# inj w/ rails
190 pump w/ tank
harness, computer, lines

With what you have, you are good up to 300 flywheel HP. A Cobra or Explorer/GT40 manifold would make that useable up to 400 HP.

Unless you have NO2 or forced induction, the stock computer will adjust very well for most street driven combinations. Turning the fuel pressure up and down works quite well to adjust the gross air/fuel ratio.

At WOT, the air/fuel ratio is a function of fuel pressure, RPM, airflow through the MAF (mass air cars only) and the TPS. The O2 sensors don't have any control input into the computer's program at WOT.

Therefore you can use the SOP meter...

Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Watch for the wind speed and direction, it can have a definite impact on your test results.

Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in.

Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.

Sorry, double post..

fastangboi said:

no im doing this on my 89gt. and its a pitb to tune the EFI without a programer. also i think its easier to upgrade a carb set up as opposed to an EFI

Click to expand...

It's not the tuning, there is a problem with your car that needs to be found.
I've seen cars nearly 600rwhp running on stock computers no chip, no programmer.

Ditch the C&L and i bet some of your problems get better. No need for a spacer either.

Putting a carb in a EFI car is a sure way to make it worth as little as possible.
You are going really really far to fix what probably would take 10 minutes by an expert.

Not sure what makes you think carbs are simple compared to the mustang efi system.
When proper parts are installed correctly, the car nearly tunes itself.

NA, carb can sometimes make more power, but you didn't say you wanted max power, you said you wanted easy to tune, which a carb is not when compared to the fox mustang EFI.

If you have problems now, installing a carb probably won't fix them, unless your problem is a bad meter, or intake/vacumm leak.

Carbs are a dying breed, not sure how you think there are more carbs out there, i haven't even seen one in like 5 years.
Carbs are alson not cheaper. EFI Intakes for a mustang are a dime a dozen.

i think its a pretty fair trade but its really dependent on how much you want to go carbd. i have had small problems with mine that are almost all gone. still working out bugs with the pcv system but everything else is perfect. i actually get better gas mileage on the highway with the carb than i ever did with the efi. i was getting about 18-19 mpg with efi and now im getting 24-25 mpg....i know it sounds rediculous but thats what im getting. now granted im getting like 10-11 around town but its a spreadbore carb that is jetted a little lean on the primaries.

fastangboi said:

i am shooting for max power and to be able to tune on the fly, easily.

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You can't get an easier tuning process than turning the fuel pressure up or down. The SOP meter process I described in my post will do the trick and it's cheap.

If you want more precise answers, get a wide band O2 air/fuel meter. You'll need one on a carb do do a good job of tuning the engine. It is something that you can use on both carb & EFI.

fastangboi said:

i am shooting for max power and to be able to tune on the fly, easily.

Click to expand...

if you want tuning on the fly than get a carb because you will be doing a lot of it. i know im having to tune my idle circuit every week because one week its 40 degrees and the next its 75 degrees and the car doesnt want to idle. kinda sucks but its nothing more than a few turns of the idle mixture screws and idle set screw

or buy a TwEECer...

You really can't look at this by the worth of each part in a dollar vs. dollar sense because all the EFI stuff costs more, so you're going to take a hit on the dollars for dollars. It comes down to what you want and if the combo you're trading for is going to make the same power.