NPI to PI engine swap how to guide

Discussion in 'SN95 4.6L Mustang Tech' started by Performance Red, Jan 15, 2008.

  1. After seeing roughly 1-2 threads per week on this topic I decided to just write a how to for it. I am writing this guide after the fact so I will take pictures of what I can, but if something doesn’t make sense to you please let me know and I will try to explain it further.​
    Ok so you have decided that your NPI engine just doesn’t provide enough power out and instead of just doing a PI head/cam and intake swap you decide that you would rather put the whole PI engine in your car. This is a relatively easy swap and this guide will walk you through what all needs to be done to get your newer PI engine running and working in your car. You will reuse your wiring harness and PCM so it is not necessary for the PI engine to have these items when you purchase it.​
    Looking over the engines, they look fairly similar but there are a few things that need to be swapped over in order for your new engine to work in your car. First step is going to be to pull your NPI engine out of the car, there is nothing especially difficult about this, just take your time and make sure you disconnect everything properly. What I did was to leave the ac compressor on the car and just unbolt it from the engine and zip-tie it to the k-member, that way you don’t need to bleed/recharge the ac system. I also unbolted the power steering pump and bolted that to the steering rack also so I didn’t need to bleed the power steering system. Once you have the engine out you can begin swapping over the pieces that need to be swapped before you can put the PI engine in the car.​
    We will work from the bottom of the engine up. If you have a 1996 NPI engine you need to swap the oil pan off the NPI engine on to the PI engine, reason being the 96 NPI engine has a sensor in the oil pan that no other year 2v has. If this isn’t a 96 you can start off with the oil cooler sensor. Near the oil filter on both engines is the oil cooler sensor, the end of the connector on it is different between the NPI and PI, all that is needed is to remove the connector off of the NPI and push it onto the PI engine, channel locks work well for this. Next comes the front cover / coil packs, you can start by unbolting the coil packs off of the front cover of the NPI engine. Next you need to remove then removing the entire front cover off the NPI engine. You need to swap front covers because the PI front cover has no provisions for the coil packs (on the passenger side PI cover there is a belt tensioner that would be in the way of the coil pack bracket and you need to reuse your coil packs because the PI engines are all COP setups.) After that is completed you need to swap the valve covers off the NPI and put them onto the PI engine as there is a sensor in the NPI valve cover that isn’t in the PI covers. Now we are up to the PI intake, all that is necessary for this to work properly is to drill and tap the aluminum coolant crossover on your PI engine for the second coolant sensor that NPI engine have, the size needed is a 3/8 npt tap. (This is the proper and best way to do this, you could also rig up a t-fitting on the other sensor and try and make that work but I don’t recommend it, this isn’t that difficult.) After that is complete you are nearly finished, all that’s left to swap over is the NPI fuel rails and engine wiring harness. The fuel rails are necessary because PI engine use a returnless system whereas NPI use a return style.​
    So everything you need to swap should now be swapped and you are ready to put the new engine in the car, after you get the engine in, bolt up the ac compressor and power steering pump if you left them zip tied in the car like I did, reconnect all the lines and wiring and you are ready to start the engine. I personally recommend the purchase of a handheld tuner with a custom tune for your pcm based on the PI engine, either a SCT Xcalibrator II or a Diablo Predator will work fine. Before you try and start the car flash the new tune onto your PCM. Now you are ready to prime the oiling system, there are two methods to doing this, flipping the inertia switch in the trunk (therefore turning the fuel off) and cranking the car in 30 second increments for roughly 2:30 minutes. Or sitting in the car with the gas pedal to the floor which also turns fuel off and cranking the car in 30 second increments for roughly 2:30 minutes. After you prime the oiling system, go ahead and fire the engine up, if you did everything correctly the car should idle smoothly and there should be no CEL’s. Congratulations you completed the PI engine swap. If you have any questions feel free to contact me on Stangnet, my user name is performance red or email me at [email protected]
    wickedwhite96 likes this.
  2. I'm surprised no one has commented. I found this very helpful as I'm having a brand new StreetMod 600 PI motor built by MMR to put into my 96 GT. Just knowing to use the oil pan, sensors and tapping that hole in the crossover was useful information. My 96 just has a red button by the left tail light for something with fuel and Idk of any fuel shut off switches but I'm sure I could find that out. Thanks for a good and informative post.
  3. The 3/8 NPT tap for the coolant sensor is a tough find. I borrowed one from a performance shop. Just a cheap tip if you need one.

    Good write up. On my old 96 I swapped a PI intake and put some Comp 268 cams in. Gave me power gains a little better to a full PI swap but an engine swap is probably a little less involved than going into the motor. Technically another engine is just a bolt on. :)
  4. Can you go into detail about the oil cooler sensor? This thread is very helpful as I am starting my swap as soon as my tranny comes back!