How To 4.6 Swap a 3.8

[MMR]

This was written by badazzstang on 3.7mustang.com.

Unfortunately this was written in 2005 and the pictures are no longer up.

Hey everyone I am writing this so that everyone on this board can get some idea on what it would take to do the basic swap that almost everyone wonders about that has a V6 mustang. Most people will discourage you into doing this swap because they say, “it will cost to much,” or “why don’t you just sell your car and go buy a GT.” This doesn’t have to be true. While getting each piee for a swap will most likely be more expensive, it can be done. I think that the cheapest way would be getting a doner car like a wrecked GT or Cobra. The way I went about doing my swap was to buy each piece separately because like most people I am not the richest person on the planet and just cant go buy everything at one time or cant go buy a whole used car. (or so I thought.) The reason I say that is that I payed 1950.00 dollars for my engine when I found whole wrecked GT’s for 1500.00. I also hope that this part list will make it easier to find all your parts and make it easier to do the swap mostly by yourself. So now on to the part list. Please remember these are the parts that I had to get to swap my 2003 3.8L 5 Speed Mustang into a SOHC 4.6L GT.

Engine - I bought mine from MPS and it was shipped to me with injector wiring harness and all accessories.

Transmission - I stayed with the 5 Speed on this one. You can buy either a T45 or a T3650. The main difference being that the T3650 is fully syncroed and the T45 is syncroed 1st - 4th like out T5’s. Also the T3650 is a little stronger. If your going automatic witch I didn’t you would be getting a 4R70W. While my engine and transmission where apart I opted for a new Ford Racing Clutch. For you people wanting to get a auto now is the time for a shift kit and/or torque converter if you want. It will save you install time in the future. I Went ahead and filled mine with Purple Royal Syncromesh Fluid. Might as well go with something good while its empty. pic of T45 used in my swap and my clutch below

Transmission Wiring - The wiring from the 3.8 and the 4.6 are different so you need to get the 4.6 transmission wiring.

Engine Wiring Harness – This is the wiring that goes from the ECU (located in the passenger kick panel in the inside of the car under the glove box) to the Constant Control Relay (CCRM) and injector wiring harness one the engine. pic of the ECU and engine wiring harness, with the starter below

Constant Control Relay (CCRM) – This is a small black box that the engine wiring harness connects to in the passenger side wheel well. It is located under the inner fender skirt.

Gauge Cluster – people have asked if they can use there 3.8 gauges. I am pretty sure u can but I would recommend going a head and getting the 4.6 Cluster. It will be the right speed reading and the right tach reading.

Hydroboost – this is the name of the brake booster used in all 4.6 powered Mustangs. Because the vacuum brake booster used in the 3.8 is to big you have to get one. You can use one from a Cobra or GT. pic of hydroboost and hydroboost attached below

Hydroboost Power Steering Lines – These are the three metal lines that come off the hydroboost brake booster that go to the power steering reservoir, the rack and pinion, the power steering pump, and the power steering cooler infront of the radiator and A/C condenser. pic below

Radiator – You will need a radiator out of a 4.6 mustang.

Radiator Over Fill – You will also need one of these because the 4.6 radiator doesn’t have a way to fill in up directly on the radiator. While the radiator and engine where empty, I went a head a fill them with new fluid mixed with Purple Royal’s Purple Ice, witch is probably a lot like Red Line’s Water Wetter. You will also need the corresponding 4.6 radiator hoses and radiator cap.

Radiator Fan - You will need a fan from a 4.6 car. I used one from a cobra so I think that any fan from any GT or Cobra will work. Just make sure u get the same year fan as your radiator or it might not bolt together.

ECU – You will need a ECU from a 4.6 Mustang.

Drive Shaft - Originally I thought that they would be the same but soon realized when I was trying to put my stock 3.8 T5 drive shaft on that the shaft was to small. I used a T45 on my swap and the T45 shaft was noticeably larger than the T5’s. I’m not sure about other transmissions though.

8.8 Rear End - While it isn’t totally need to actually run but highly recommended would be getting a 8.8 rear end out of a GT the same year as your car.

K Member – I have heard different things about this, if you are putting the 4.6 into any Mustang 96+ then you don’t need one. If you are putting the 4.6 into a 94-95 then yes you will need one, the 94-95 have different mounts on the k member and actually sit farther forward and lower I think. (was told this by a guy doing a swap on a 95 to a 4.6 that’s why I cant remember exact details)

A/C Lines – You will need A/C Lines form a 4.6 that go from the condenser in front of the radiator to the inside of the car and the compressor. They are different from the 3.8 lines.

Dual Exhaust - Here is the time that if you don’t already have it to get it. I had long tubes on my 3.8 so I just used the same h pipe and cat back making it a little cheaper. I would highly recommend putting in a aftermarket header while your 4.6 is out of your car. They are extremely hard to put into your car when the engine is in the car. I when with MAC long tubes witch will make the engine a little and I do mean little more difficult to install but is worth the effort.

Intake Tube – You will also need one just because I think we all know they are different. I got a cheap Cold Air Intake off of ebay to hold me over until I get a better piece.

The main fuel line on the 99+ enter on the front of the engine on the fuel rail on the 3.8 engine and enter on the back of the fuel rail on the 4.6 SOHC. But this is ok. I just tucked mine down and used the 3.8 fuel line with no problems.

I used my 3.8 throttle body cable. I thought that I would throw that in I case someone was wondering. The same with the cruise control cable.

Now if you are piecing this project together you will most likely have a Passive Anti Theft System Problem (PATS). When the code in you transponder keys doesn’t match the code programmed in the Gauge Cluster of the ECU then it will cut the fuel to the car and not let the injectors fire. Ill give a slight description that I got about the PATS system. When u turn the key on you car to start it, a receiver gets the code on you transponder keys. When it receives this code it sends it to the gauge cluster. After the gauge cluster receives this code and everything matches then it sends the code to the ECU to let the engine start. If just one of these pieces (keys, gauges, or ecu) are not from the same car then most likely you’ll have a PATS problem. The PATS system can be overridden by ford dealerships by the WDS computer they use. To do this you will have to buy two new keys that are about $51.00 a piece. The WDS system has a 10 minute delay to access the system but after that the dealership can program the new keys and makw sure the Gauge Cluster, ECU, and the Keys are all in sync.

here are some places i got my parts

www.stangparts.com

www.car-parts.com

www.ebay.com

www.50resto.com

if anyone needs any help fell free to email me at bimmer1999@aol.com or im me on AIM at bimmer1999. or just leave a PM. if needed ill give u my cell number if you need any additional help or need a one on one. im gonna try to add pictures of everything i described so it will be more clear.

Link to OP: http://3.7mustang.com/vb/f87/how-4-6-swap-3-8-a-136405/

[Det_Riot]

Good article! I think the easiest way for this or the 5.0 swap to work would be just to get a wrecked one and swap everything over.