Fox Body Mustang 4 Cylinder to V8 Conversion

Fox Body Mustang 4 Cylinder to V8 Conversion

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Fox Body Mustang 4 Cylinder to V8 Conversion

Posted 2/19/2015 by Jay Walling


Have you been thinking of swapping your 4 cylinder Fox Body to an 8 cylinder? This 2.3 to 5.0 swap guide will give you all of the basic info you need to know before tackling this project!

FOLLOW: 79 93 mustang , mustang , v8 , 4 cylinder , swap

“4 to 8” How to swap a pushrod 302 5.0L into a 4 Cylinder Fox.

Most of you may be asking “why swap an older 5.0L when I can save up buy one in the first place?” Well some of us already have the emotional attachment to our ride and would like the added power gains of the V8 platform.

Most of these kinds of swaps can be rather cost effective and can be one of the deciding factors to do a swap rather than finding a used GT or LX 5.0. Depending on what part of the country you are in, and the condition of the car you want to swap, I have seen many Fox Bodies out there for under $500. Not to mention that 4 cylinder chassis’ 9 times out of 10 have substantially less amount of wear and tear on them than a V8. They are the perfect platform to go with in most cases. Torque boxes are the prime example. With less than 100 HP on most factory 4 bangers, the likeliness of you having to do structural repairs are slim to none. Sourcing the V8 parts needed to do the swap properly can be tedious, but if you are able to find a good freshly wrecked car, this is usually the way to go. Salvage yards, Craigslist, eBay, forums and Facebook are perfect ways to source hard to find items. Our friends over at prestigemustang.com have helped out on many of swap projects in the past. In this write-up, I will go over the basics on what goes into this swap, and give you the "ins and outs" of what to expect.

The majority of this section will depend on how wild or mild you want to take you build. You need to ask yourself “do I want a stock daily driver or a 1000 HP beast?” This is the best time to determine the route of your build. Here we will be going over the stock 5.0L end of the spectrum. Like I said before, finding a wrecked V8 platform is the easiest way to go. Engine, transmission, differential, wiring, suspension, and brakes all come into play on this and depending on the condition of the “donor vehicle” you may want to source otherwise. Let’s just say you did get a perfect wrecked car, and all of the needed items are intact. What all do you need to pull off and swap over?

First, of course, is the engine and transmission combo. This will be the base for all of the other components going on the car. The 4 cylinder transmission out of a 5 speed will not swap over to the V8. 89-93 mass air equipped vehicles are ideal for their ease of operation. Along with the engine and trans the PCM and wiring from the V8 is another major factor. From the bulkhead forward the V8 and 4 Cylinder cars are almost completely different. The PCM will need to be the proper unit either for an automatic or manual transmission. Here again, if the donor car is an 89 and the swap car is also an 89 this would be best. With the PCM covered, let’s go to the other engine sensors.

The MAP will be one key component; non-mass equipped cars will have a different unit than a mass air vehicle. Using the incorrect unit can cause surging issues and idle problems. Alternator harnesses will need to be correct from corresponding years as well. If you are able to source the proper-year components, the rest of the sensors and wiring will be a straight-forward process.

Vacuum routing and placement is key when doing the V8 swap. You will need to change over the V8 vacuum tree located on the driver’s side bulkhead under the hood seal. Make sure all connections go to the correct locations or are capped off if not in use. Improper vacuum routing can also cause drivability issues.

The throttle and clutch cables are specific to the V8 platform; the 4 cylinder version will not be able to be reused. Smaller items like the power steering will be fine to use, although the 4 cylinder line has a feature to cut off the A/C when pressure is applied. The sensor on the line can simply be capped off or you can swap it for the V8 one.

The cooling system is the next step in the process. You can reuse the radiator from vehicle to vehicle. The fan and shroud from the 4 cylinder application will need to be tossed away to the side. The V8 will take a specific manual fan, clutch, reservoir and shroud units. The drive-shaft will be able to go from the old to the new if need be.

The fuel system will need to be reworked as well. The lines, although are the same size of the V8 will need to be swapped over due to connection differences. The tank and pump both will be able to be reused in the swap. This is the perfect time to change them out, depending upon the condition of them along with the fuel filter.

Exhaust components such as the headers, mid-pipe, and catback are integral to the swap also. You can utilize the factory components, or this would be the best time to upgrade since the drive-train is out of the car. If you have ever installed a set of long-tubes, you know what I am talking about.

Lastly let’s dive into the suspension, brake and rear end upgrades. The stock 4 cylinder suspensions will “work” but it is best to upgrade to the beefier V8 units. The K-member and front lower a-arms will be perfectly fine to reuse. The springs and sway bars, however, I would recommend using the ones from the V8. They are larger and can handle the added weight of the V8. The front brakes on the 4 cylinder cars are smaller than the V8 units. Along with the new rotors, calipers and pads; the V8 spindle and front strut must be taken from the V8 car. Also, with the brake end of the swap the V8 hard lines would need to come over as well. The rear end on a 4 cylinder car is going to be a 7.5” configuration, whereas the V8 will be 8.8”. The 8.8” is designed for the V8 output and would be highly recommended in this swap. The factory equipped drums will be fine to use on this setup. Depending on the year car that the V8 is going into, you may be able to utilize the quad shock assembly on the differential. This serves as an extra stabilizer for the rear end assembly.

I have mentioned upgrades in some of the sections. When doing the swap, this is going to be the most opportune time to upgrade existing components.

I hope this has been a help for commonly asked questions in regards to the V8 transplant. For your entire Mustang needs always check out LMR.com!


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