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What's involved in installing a 5.0 in a 1991 4 cyl Mustang

1474 Views 5 Replies 4 Participants Last post by  hoodrat
does any body know how much trouble it is to put a 5.0 in a 1991 4cylinder convertible mustang... a friend of mine is about to try it. if u guy have any info it would b greatly appreciated! thx.
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Let's try to get your question answered in here.
Theres a real good sticky on the top of the page just about what youre asking.
does any body know how much trouble it is to put a 5.0 in a 1991 4cylinder convertible mustang... a friend of mine is about to try it. if u guy have any info it would b greatly appreciated! thx.
Here is some info that should help get you started......

V-8 Conversion for a Fox Body Mustang

Okay everybody knows the easiest way to get rid of your 4 banger and put in an 8-cylinder is to sell your existing car and get what you want. But this isn't always an option due to finances, insurance considerations, or just liking a challenge. The second best choice would be to buy an existing V8 parts car and start swapping everything you need. Sometimes this route isn't practical either. This article will try to show you what is needed to make your car into a V8.

This article is written from the perspective of dropping a 302 in a 79-93 Mustang (or 79-86 Capri) but much of the information is the same for any fox type chassis (1980-88 T-Bird / Cougar, 1978-82 Fairmont / Zephyr, 1981-82 Granada / Monarch, or 1983-? LTD / Marquis). Sometimes the parts for your swap will vary depending on what car you are starting with and what engine you plan to use. In those cases I'll try to provide what I think will work, but some trial and error on your part may be necessary.


Parts List and Helpful Hints
Engine: Of course if you’re going to put a V8 in you first have to get one. There are many routes to go from build it yourself to used (scrap yard) motors to crate engines. Just be sure you know what you are getting, check the year of the motor, what type of shape it is in, history, and how many of the peripheral pieces come with it. Many of these little extra items can save headaches in the long run.

Balance: To get the correct flywheel and harmonic damper, the balance of your engine must be known. Basically pre-81 302s have the 'early' imbalance of 28 oz.-in. If the 302 is 82 and later it will be 50 oz.-in. imbalance. WARNING: rotating parts such as the damper, flywheel, and crank cannot be mixed between the two systems without having the entire reciprocating assembly rebalanced.

Fuel Pump: Fuel injected motors or cars have electric fuel pumps. That means if your motor came from an FI car a mechanical type pump (for carb.) will not work unless you change the timing cover or if you have a FI car and using a carb'd motor a new pump will be required that is low pressure (less than 15 psi) along with a regulator.

Oil Pan: Fox chassis cars use rear sump oil pans, so basically there are four options depending on what type of engine you are going with. First, if you are going with anything other that a small block (i.e. 351C, 400M, 460 cid) you must use a conversion kit type pan. Second, for a race type application go with an aftermarket pan that has baffles of some sort. Third, for an engine that has the oil dipstick that goes into the drivers side of the block any fox body 302 oil pan will work, for a 351 use the Ford Racing Performance Parts (FRPP) pan. Last, on a 302 that the dipstick originally entered the engine on the timing cover (front sump), the factory 78-about 81/82 oil pans have the dipstick enter on the drivers side of the pan (see picture) which makes them the hot setup for putting an older 302 into a later model.

Distributor and Ignition: If you start with a car that already has the Duraspark II system then you are miles ahead. If not follow the "Ford Duraspark II Ignition System" tech article on this website to hook it up. The basic components needed are the ignition module, any coil, and a distributor. Use the '85 Mustang stick shift distributor with a roller cam, other wise any '74-'84 Ford distributor will work (except FI distributors). Don't go the points route unless you enjoy changing the points every 3,000 miles. One last option for a hi-po street or strip car is the aftermarket parts - MSD, Mallory, or Accel all are good choices.

Wiring Harness: For a carb'd car the only things necessary to have it run are compression, gas, and spark, everything else is extra. Same goes for the wiring harness - all you need is a hot wire to make the ignition work.

Radiator: There were 2 different factory radiators commonly used in garden variety Mustangs. One was smaller, top / bottom tank design used on early 4 cylinder cars, usually mounted using a sheet metal extension to get the radiator closer to the engine. The second was a 2 core cross flow design. The cross flow design will work on a mild 302 if it is in decent shape. Don’t even try the smaller it isn’t big enough. For any type of high performance application get a new 3-core copper or aluminum radiator. Also always run a thermostat - engines will have dramatically less wear and perform better at the correct operating temperature.

Accessories: There are a ton of different ways to go here. Obviously if this comes with the donor engine it is the easiest. Since there are so many different variations these are the guidelines - 1) make sure you spin the water pump and fan the correct direction (V-belts are always clockwise), 2) The 4-cylinder alternator will work on your V8 w/ the correct brackets, 3) 302 & 351 brackets are not interchangeable, 4) If starting from scratch just go to the junkyard and get what you need, 5) Pulleys out of alignment will not only reduce belt life but also cost extra horsepower, 6) clutch fans use less power than standard type fans, 7) both the dowel pin and bolt circle pattern are smaller on the standard rotation water pumps vs. the reverse rotation water pumps.

Bellhousing: This depends on the transmission your are using but the 4 basic ones are the standard transmission bellhousing for a T5, standard transmission for the SROD or Toploader 4-speed, the auto bellhousing for a C4, and the auto bellhousing for the AOD. Other combos are different still such as the Tremec. The best way is to get the bellhousing with the tranny if possible. Remember that for a stick and quarter mile time faster than 12.00 seconds most tracks require a scatter shield or blowproof bellhousing.

Transmission: Once again the options are wide open. For a light duty application the T5 from a 4-cylinder or a SROD are the cheapest overdrive options, just don't plan on using slicks, dumping the clutch, power-shifting, or going faster than 14.0 in the quarter with these. Other options include the AOD, T5, Tremec, C4, and the Toploader.

Special Notes on Using C4 Trannies: I do not know much about automatic transmission but can say that be careful when getting a C4 for a Mustang. Ford changed many things over the years including input spline count, pans, fill tube location, servos, and shifter direction for column or floor mount. Be sure to choose what is best for your application and trial fit everything.

Driveshaft: A V8 will require a shorter driveshaft than all the other factory engine combos. There are basically 3 factory driveshaft lengths available. The longest is the 4-cylinder 4-speed or C4 driveshaft with a 7.5" rearend. The next shorter by about 1.5" is the V8 and 7.5" rearend. The shortest is the V8 and the 8.8" rearend combo that is still another 1" shorter. If you are going from the longest to the shortest in the 3 combos above then plan on getting your driveshaft cut and rebalanced (about $90) or get the right shaft. The length you are looking for is 45.5" from center to center of the holes for the U-joints. This length will work for any 1979-1995 Mustang / Capri 5.0L with T5 / SROD / C4 / AOD transmission and either a 7.5" or 8.8" rearend. The slip yoke on the T5 / SROD / C4 / AOD transmissions are all the same at 28 spline. The flange for the rearend is the same for the 8.8 and 7.5 also, but a 9" is different. Another couple of options are the FRPP aluminum driveshaft or the '93 Cobra driveshaft. Both are able to handle higher torque due to larger diameter shafts and bigger U-joints.

Rearend: The stock 7.5" rearend will live if you plan on a mild combo (same restrictions as the SROD or 4-cylinder T5 above), otherwise get the 8.8". Thunderbirds make good donor cars for 7.5" rearends because many of them came with 3.45 gears and locking differentials. Although the Thunderbirds used a slightly wider drum to drum length it will work just fine in a Stang. For everyone’s info - the axles and brakes between an 8.8" and 7.5" are the same as long as the drum to drum length is identical.

Pedal Assemblies: If you are going from an auto to a stick then you also need the complete brake / clutch pedal assembly from a donor car too. Stick cars have a wider accelerator pedal that is easier to find and press when necessary so get it too.

Tach: Most Ford Fox body cars have a switch on the tach to go from 4, 6, or 8 cylinder cars. Some such as Mustang Turbo or Thunderbird Turbo models will need to convert theirs to work or use an aftermarket tach. For the conversion see the "Using a 79-82 Turbo 4 Tach" article elsewhere on this website. BTW - contrary to popular belief, the factory Ford tach is not as inaccurate as some claim, and most importantly it is very repeatable. I calibrated mine and it works great.

Suspension: This really depends upon personal preference. The hot street / strip setup is to keep the 4-cylinder springs and sway bars. I drive mine like this everyday and love it. In any case an upgrade to better rear control arms and torque box reinforcement is recommended. If you are into carving corners go with a suspension package from any of the places in the Mustang magazines. For those into handling be sure to read the Mustang Performance Handbook Vol. 2 - it details all you’ll ever need to know about making a Mustang handle.

Chassis: Already noted above is the rear torque box reinforcement but also a good set of welded in subframe connectors are a must.

Front Brakes: The fronts are either 10" or 11" depending upon year and engine combo. Upgrading the master cylinder and front brakes to the later 11" ('87 and up rotors will help shorten stopping distances. You need the master cylinder, rotors, calipers, brake lines, and spindles. You can use your same struts but the bolt spacing where the spindle bolts up and the spindle width are different, so be prepared to do a little grinding and get some washers to take up the slack. One more interesting upgrade if you are going with the 11" front brakes is to use '84-'92 Lincoln LSC calipers. They have a larger bore vs. the stock Mustang 11" brakes (73mm vs. 65mm). Be sure to match the correct Lincoln master cylinder to system for optimum results.

Rear Brakes: The rear brakes are the same for all Mustangs (I have heard of bigger drums on early Fairmont Wagons but I have never found any --> UPDATE - Since I first wrote this two people have confirmed to me that 78-79 Fairmont Wagons have 10" diameter rear drum brakes vs. the Mustang 9" diameter). The biggest problem here is the rear brake line. If you plan on dual exhaust you need the rear brake line that runs from the connector on the passenger side fire wall to the rear middle of the rear end and the corresponding section on the rear end. (See the exhaust system section for more explanation).

Exhaust: Best bet here is to get Mustang specific parts. Cheapest route would be factory headers (used about $40) and a used H-pipe (gut the cats) and a factory 2 1/4" mufflers and tailpipes. This is a lo-po, low budget setup but works great. A much nicer setup is aftermarket headers, off road pipe, and a cat back system (I personally think MAC is the nicest), but be prepared to spend about $500 for a new system.

Any dual exhaust option requires the rear brake line to be in the center of the rear axle. Most 4-cyl and 6-cyl cars have the brake line on the passenger side of the rear axle tube. This is right where the pass. side of the dual exhaust goes so get the correct line. Another consideration for pre '85 cars - the last exhaust hanger holes for the pass. side tail pipe many need to be drilled. It will require a right angle drill or clamp and weld the bracket to the frame (not real easy to do where it is located).

If a single exhaust system is an option then a replacement '79-'84 single exhaust with dual outlet muffler is pretty cool looking and you won't have to replace the rear brake line from the front to the rear. Exhaust hanger holes are all in place for the single exhaust option as well.

One last note on exhaust - not all exhaust manifolds exit at the same place, therefore make sure your y-pipe or H-pipe is compatible with the exhaust manifolds / headers you will be using. If not be prepared for a trip to the muffler shop for some fabricating.

Hood Clearance: This is generally not a problem on most installations with a low-rise manifold and a low-rise air breather. Problems begin to come in if you go with 351 or 460 cid installations. If it is close my first suggestion is to use a shorter air breather with a K&N snub stack. A little tougher but better for performance is to go with a hood scoop or cowl induction hood. Another option that many people have had good success with is the Ford Racing 13" chrome air breather assembly or a K&N 13" filter assembly. You may also consider cutting the hood support beam above the air cleaner for a little additional clearance.

Power Steering Pump: This is more of a word of caution about interchangability. The 5.0 cars have a higher pressure pump to work with the rack, otherwise the pump can't keep up on tight roads and will momentarily lock the steering - MOST UNCOOL.

K-member: The only k-member that is not compatible with a V8 is the straight 6 (200-cid) k-member. It only appears in '83 and earlier cars. The best factory k-member is the '87 and up model only because it weighs about 10 lbs. less. The ultimate is a tubular k-member and all the tubular and coil over accessories to go with it - but at those outrageous prices who can afford it!

Motor Mounts: The '93 convertible mounts are the best if you must buy them new, otherwise any 302 mount will work. Using a torque strap will help save the mounts from being ripped apart in high stress situations. Stay away from solid mounts unless you like a lot of extra vibration in the car - I would only use them on an all out race car myself.

Transmission Tunnel: Cars originally equipped with T5s have a slightly higher (about 1") tranny tunnel. Expect to do a little trimming with the tin snips when putting a different manual transmission in the car than what came in it. Remember any tranny will fit if you have a big enough hammer, some snips, and a welder.

Transmission Cross-member: This all depends on if you have single or dual exhaust. Single exhaust uses the single hump cross-member that most already have. A double hump cross member is required for dual exhaust but will also work on a single exhaust car. The famous double-hump cross-member can be found in any '86 and up V8 Mustang. If you are converting a 79-81 car the cross-member mounts on the frame are only 2 3/4" wide vs. 4 1/2" wide on the 82 and up cars. This is not really a problem just cut the pipe extensions on both ends of the double-hump cross-member to fit your car.

Wheels and Tires: Just some pointers here - cars before '90 have slightly smaller wheel openings on the front therefore when using 16" wheels or bigger the tire may rub on tight parking lot turns. The second thing is 265/50-15s are about as big as it gets for the rear. Trimming the wheel lip and using a big hammer on the inner wheel housing will be necessary to help clearance. Third, early cars have bigger wheel lips on the rear than the later cars so expect to trim with big tires. Last, if you like them (and I do) the cheapest set of 16" wheels you can get are the '87-'88 Thunderbird Turbo Coupe - that's what I run on the street with P225/55-16 tires.

Quad Shocks and Rear Sway Bar: Both are your friends in helping your car hook up and control wheel hop, so if you score these items consider it a big step in the right direction.


Final Thoughts
A few specialty Mustangs that I didn't say anything about are the SVOs, Saleens, and the 93 Cobras. If you come across any of these cars being parted out or sold cheap during your conversion then get everything you can. The suspensions and brakes on these cars are better than anything you will find on any other Mustang.

As you can tell this is not the simplest thing in the world to do but it really isn't that hard either. If you have average mechanical skills then the swap should be no problem at all. Having the knowledge of what will work and what will not is 50% of getting there. So after reading this consider yourself half way done. The other 50% is changing parts and problem solving. Good luck.

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your better of getting a donor car! also 91 car requires a 91 5.0 computer harness , good luck
thanx for all the info guys, will the 5.0 motor mounts just bolt right up or do they have to be welded in place? the 4 cylinder auto trans won't bolt up to a 5.0 will it? thx
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