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Mustang EFI To Carbureted Conversion Guide

Created by Jay Walling
Date Created: 1/29/2019
Last Updated: 11/18/2022

If you are looking to convert your factory EFI Mustang over to a carbureted setup, review some highly important details before making the leap!

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In this article, we will go over some of the general components and the pros and cons of these swaps. Going from your factory 1986-1993 EFI to a carbureted setup is actually not as easy as most would think. There will be a few different areas that we will cover on this swap within this article.

Mustang EFI To Carbureted Conversion Guide - Mustang EFI To Carbureted Conversion Guide

FUEL SYSTEM

For your fuel system we will start at the rear of the car with the tank. The best overall route to go is to try to retain your factory tank at all costs. This way you can retain your factory fuel level sending unit and the communication with it and the factory gauge will stay the same. This will benefit you down the road if you ever had to replace this, you do not have to remember what option you had to put in there to make everything work. Your factory fuel pump hanger would need to be ditched on these swaps. The high-pressure in-tank pump would no longer be valid anymore. One of the easiest options to go with is our part number LRS-4010. This will allow you to retain the factory tank and eliminate the factory hanger with one part number.

From there you can utilize custom lines using the popular AN style fittings to your low-pressure pump. Our friends at Holley offer the tried-and-true Holley inline electric fuel pump. This pump will also include the needed regulator to dial in your setup. Carbureted applications normally average 5-7 PSI whereas EFI applications can run around 35-40 PSI.

You can also go with a mechanical setup, but this will require you to change the front timing cover over to one that has this provision built in to run the pump; also a fuel pump eccentric would have to be added for proper operation. Either route you go with will require the use of custom lines for the entire car.


ENGINE COMPONENTS

Your factory intake manifold and fuel injection system would be eliminated. This will also include most of your EFI wiring harness and associated sensors for this setup. Choosing a carburetor will always depend on the particular setup you have. Your best bet is to consult with your engine builder for the size to go with. This will also apply to the intake manifold. With the 1000’s of different possibilities and combinations out there, it is best to consult with your engine builder to determine the best choice for your particular build. Your factory intake track, including mass air if equipped, would be next. This would then be replaced with the traditional style air cleaner on the top side of the carb. As we mentioned in the fuel system portion, if you do choose a mechanical fuel pump, the swap over of the front timing cover is necessary. Vacuum routing and deleting some ports can also be needed.


IGNITION SYSTEM

The best way to go about doing this will be to use the factory components from the carbureted years of Mustangs. This will include the 1979-1985 style distributor, ignition coil, Duraspark, and associated wiring. These parts will allow your new system to function without the factory PCM in place.


PROS AND CONS

Overall there can be many pros and cons to doing this style swap. Knowledge is key, your mechanical skill set and overall understanding of carbureted setups is a must. Carbureted configurations are becoming a lost art honestly. Tuning can be an issue if you do not know what you are doing. Modern-day EFI engines will automatically adapt to elevation, air temp, and ignition timing changes. Carbarbureted setups cannot do this; you would have to manually fine-tune these parameters yourself. In some cases, these tuning procedures are becoming a lost art.

Cost is another factor since you are starting with a car that is not factory equipped with a carb, you will be spending a lot of your build funds on components that may or may not be actually benefiting you in the long run. Most people still feel that going carb is more reliable than EFI, but in most cases, this is not true. The advances in technology have really made carb setups a thing of the past. For example, something like the Coyote platform and these engines' power produces. Emissions are another issue that you can have with doing a carb swap. With new laws coming down the pipeline every year, this is becoming more difficult to do on a factory EFI-equipped car. If you plan to have an actual off-road/track use-only project, you would not have to worry about this.


I hope this general overview of our EFI to Carbureted guide has helped you make your decision. For all things 1979 to present Mustang, make sure to check out LMR.com.


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About the Author

Jay has written content for Late Model Restoration for over 10 years, producing over 120 articles. Jay has an extensive 25-plus-year background in automotive and is a certified Ford Technician. Read more...