[Written by 86mister2]

This is my engine swap write-up for a 1988 USDM 4A-GZE into a 1986 USDM Mk1. This swap is straight forward mechanically but the difficulty of wiring varies depending on model year. If you use your N/A model's transaxle it is 100% bolt in. If you want the S/C model's transaxle you will need to do engine mount modifications not discussed here. I hope that this write up will help others discouraged by the false conception of extreme difficulty. 

All wiring references written here are for 86 model year only.  If you use this guide to swap into a different model year be prepared to do wiring diagram research to make sure you have it wired correctly. Due to my inexperience with other model years, I will not be able to provide much assistance if you run into issues. However, I am told by others who have done the swap that all 87+ Mk1's are compatible with any USDM Mk1 4A-GZE. This means the engine harness and body harness are Plug 'n Play.

The following information covers my engine swap. I started on the last Monday of April 2004. I was finished and cruising the streets the following Monday. I only worked several hours a day. I wanted to pace myself to make sure all went to plan.

OK! After months of procrastination I finally began my engine swap today.  My goal for the day was to have the 4AGE and the fuel tank out of the car. Well, things didn't go as planned. The damned car just doesn't want to come apart!!! So after many hours of fighting and bitching with it, I finally closed shop for the day, the factor being that the only socket I had that remotely fit the 30mm axle nuts stripped out and cracked down the side. My monster 400 lb/ft air impact couldn't break the damned nut loose before it literally ate up the socket!

So here is what was accomplished today.
Below you see the engine compartment is starting to look empty. The battery, airfilter with AFM are out.  All wiring, hoses and cables are disconnected from the engine. The engine wiring harness will remain plugged into the motor and will stay with the engine as it's removed.  You can see it draped over the engine.

Not much to see down here. The entire exhaust system, except manifold, has been removed because everything after the manifold was welded together. On the '88 SC that I stripped, the exhaust was all stock so I was able to unbolt it piece by piece and leave the B pipe on.  It was a bit awkward to remove in one piece, but not that difficult. The hardest part was getting to the nuts that hold the B pipe to the manifold.

That's all I was able to accomplish without removing the axles. They're soaked with Liquid Wrench right now to help penetrate and break them free. I'll give them another spray down before I'm off to the car parts store in the morning for a bigger socket.

OK, so I got my engine out on Tuesday, but was in a really bad mood so I didn't post the updates...

I started first thing by going to Kragen's Auto Parts and getting the proper 30mm axle nut socket. $17 dollars later, the axles are out.

The magic socket:

After the axles were out I hooked up the cherry picker removed the engine mounts. As I was lowering the engine down to the ground it kept getting caught on something and was getting stuck crooked.

After some finagling I was able to drop it out nice and smooth. I just had to sit up on the fire wall between the engine compartment and the trunk to pull the engine over towards the left while I dropped it down.

After I got the engine out I hooked up the cherry picker to the chassis and lifted the ass end up to clear the engine.  I then dragged that sucker out from underneath. I rested the chassis on jackstands way up in the air so I can get under there to drop out the fuel tank. I then put the engine back on the cherry picker and split off the tranny.

I was hoping to be able to re-use my old clutch since I'm on a tight budget, but of course that was not possible. I split off the pressure plate from the flywheel and found this:
Pressure Plate:

Disc:

Flywheel:

As you can see, the flywheel and pressure plate have a lot of heat discoloration on them.  What you can't see is the warpage and raised spots on the surfaces.  Also you can kind of see the uneven wear on the disc's friction material. This clutch was on its way out.

Here's the end of Tuesday, ass end up on jackstands and everything put away:

New clutch and pressure plate:

New throw-out bearing, clutch alignment tool, and white lithium input shaft grease:

This clutch, though OEM spec, appears to be a beefier design than the Toyota clutch, so we'll see how it handles the GZE.

That's all for now, I plan on dropping the fuel tank tomorrow to change the pump and getting it back in, as well as getting the engine and tranny mated again and back into the car.

I woke up this morning and tackled the fuel pump.  For the most part this was a pain in the butt but not as bad as I had thought it would be from other's testimonials.  When dropping out the tank, you should start by removing the rear storage binnacle and the center armrest console cover to expose the wires for the fuel pump and the fuel level sender.  After the wires were disconnected I had to remove the coverings on the bottom of the chassis to expose the tank, the radiator piping and A/C lines and such.
I disconnected the e-brake system to get it out of the way as well as a few other lines.  If you look, you can see everything dangleing off the bottom of the car:

After all cables and what-not are out of the way you can undo the metal straps that hold the tank in.  More than these straps hold the tank in it seems, as after the straps are undone the tank won't just fall to the ground.  I had to massage it out from inside the tunnel. When it finally comes loose, just be ready for it to drop.  I also noted that the small lines that are difficult to disconnect and reconnect don't need to be disconnected at all!  There is this weird metal tube with other hoses that connect to it that runs up the middle of the cab-to-engine compartment firewall, normally under the plastic cover.  This is the piece I'm talking about with all the little pipes going into it.  You can unbolt it from the car with most of the hoses still intact (the ones in the back that are really hard to get on and off can be left on for this procedure) and just drop it out with the tank.  In this pic, you can see it still attached to the tank out of the car.

This made re-installation 1000 times easier!  Installation was reverse removal.  I tied some string to the wires for the fuel pump and fuel level sender so I could easily pull them back up through the chassis tunnel.

While I was reinstalling the tank, the car parts store called and told me that my flywheel was in so I went to pick it up after I finished with the tank.  So I get the new flywheel on no problems.  While I was torquing down the pressure plate one of the studs snaps INSIDE THE NEW FLYWHEEL!  I was very angry, needless to say, but some slow gentle persuasion was able to back it out.  I then recalled seeing an almost identical bolt that hols a cable sleeve thingy for the e-brake.  This became my replacement.  The whole dilema took about an hour to solve.  So after I get the clutch assembly back together I work on mating the tranny back up to the block which was not an easy task.

Clutch alignment wasn't an issue after I got some help.  It was just too awkward for me to get everything ligned up properly to get the tranny on by myself. About 45 minutes later I was finally able to get them together.  So far this was the hardest part of this whole ordeal.

A concern I'm having is the amount of free play in the clutch release fork. It seems at stationary position that the slave cylinder is already pretty far extended. I'm not sure how much this clutch is going to be able to release.  If I have to pull this engine out again I'm going to be very unhappy.  Here's the engine mated to its new 5 speed C50 gearbox.  I say new because this engine came with an auto.

That's all I did today.  Tomorrow I'm going to start off by lengthening the wires on the harness for the starter and the O2 sensor then the engine goes in.  After I get the engine in and supported on its mounts I'll get everything that needs to be hooked up from underneath back on and put Mister 2 back on the ground. Once that's done I'll roll him out to swap out the 86 wiring harness for the 88 so i shouldn't have too many crazy wiring issues to deal with.  I'm hoping to get that all done tomorrow.  If I have extra time I'll get all the fuel hoses and coolant hoses and everything hooked back up then try to get the air ducting and intercooler seated. I also have to go back to the store to pick up fluids and some serpentine belts.  If everything goes well, I'll be running by Monday!

I started this morning by going straight for the engine. I was going to lenghten some wires but decided to put that off until I do all the wiring.  Instead I concentrated on getting the engine in and let me tell you, this was NOT easy.  It took me about 3 hours to get the engine raised into position then bolted in.  I had everything you can imagine go wrong today from broken tools to broken vacuum switching valves. It was a long hard battle, but it's finally in!

After the engine was mounted in I worked on getting my axles back in, and getting A/C lines, oil cooler lines, clutch slave line, and coolant lines hooked back up. I wanted to get everything on the bottom hooked back up before I set Mister 2 down and rolled him out.  I'll still need to get back under there to bleed the clutch and hook up the shifter lines as well as install the starter and hook the exhaust system up.

 Mister 2's new powerplant installed, waiting for the finishing touches.

Aside from what I said needs to be hooked up down below, up top I still need to hook up the fuel lines, swap all the 86 electronics (coil, ignitor, injector resistor pack, etc.), and install the air ducting.  bI also need to run the 88 SC's body harness up into the cab.  I also need to get two new accessory fan belts, oil and coolant. On top of all that I need to figure out a replacement for this VSV I broke which controls the supercharger's air bypass valve:

 I also need to find some crush washers to finish up the fuel lines.

Getting the engine installed and mounted took most of my energy today. I'm very tired and sore after what I had to go through to get that sonofab!tch in. If health permits. I'll finish it up tomorrow.

All I did today was work on modifying the 86 body harness to accept the 88 SC GZE harness. I got it back in and all hooked up, but the ECU isn't getting power it seems, and the fuel gauge drops to empty, even though there's half a tank....

I'll spend tomorrow trying to work out the bugs. And if I get it figured out, I'll put the belts on and fluids in, and see if she wants to start up!

OK, I'm proud to say that as of yesterday evening, the swap is complete and the engine runs like nobody's business! This will be my final write-up to finish this up.

I spent the whole weekend working on the wiring harness. At about 8:00 Sunday evening, I got all the wiring gremlins worked out with the help of a fellow board member's write-up found HERE and the car was ready for final assembly starting early Monday morning. This pic shows the harness in the cabin, no changes were made to any of this:

You can see some long stray wires coming from the kick panel fuse area. These are wires left from the old aftermarket alarm which is long gone. I ended up cutting out these wires and using them to extend the wires for my O2 sensor. I also took the starter main feed wire out of the 86's harness as it was longer to reach the starter in the back, and I used heavy 10 gauge wire to extend the starter's solenoid power. You DO NOT need to extend these wires if you have a C-52 with the starter mount under the intake and use the SC's exhaust system pieces. My C-50 transmission has the starter mount under the exhaust manifold where stock auto GZE's had it under the intake. That's why those wires were extended. And I had to extend the O2 wires because I kept my 86 exhaust system, which mounts the O2 at the bottom of the manifold, as opposed to the GZE's stock system which placed it right before the flex pipe.
Below you see the modifications to the 86's body harness. There were some big changes that were explained in the procedure I posted a few lines above. Note that there were many wiring harness changes over the years, and even several for the same model years. His write-up did not work 100% for me, but it put me pretty damn close. I had to figure the starter circuit out for myself, but everything else was spot on according to the write-up.

The few stray wires you see are for a few accessories like the octane selector switch (Red Wire), the SC on indicator light (Yellow Wire), and for the center high mounted stop light (Yellow with Red Stripe).

In the above pic, you can see the 3 wires I had to add. The black wire runs from the ECU to the Check Engine light, the green one is for the engine bay cooling fan, and the red one controls the injector relay, and had to be spliced into the wires for the injector relay's pin 4.

Here is all the modules and the ECU plugged in inside the trunk.  You can't see the voltage regulator, cooling fan computer, or speed controller (cruise control controller) in this pic but they're there.  The green box is the 86's speed controller.  I used the 88's which is a lighter shade of green which is just out of the picture.  The modules still need to be mounted to the rear firewall. I might take care of that tomorrow.

SOLDER ALL YOUR WIRE SPLICES! IT IS THE ONLY WAY TO DO IT!
You don't want cheap butt connectors and the like falling apart on you leaving loose ends everywhere and possibly causing the demise of your wiring and/or electronics.

After the wiring was done I spent the rest of the day putting all the little things like fuel line crush washers and vacuum lines back on. Once everything was tip-top up top I concentrated on the bottom where I still needed to install the oil drain plug, accessory fan belts, exhaust system and clutch bleeding.

Clutch bleeding was a breeze, so was getting the exhaust back on.  I had to go to the car parts store like 4 times to figure out the right belts since the exact ones the computer listed were out of stock and would have taken months to get. After those were taken care of I put the oil plug in and filled 'er up! I also started bleeding the coolant out and double checked all my wiring and components while it was burping.

After everything was done I got in the cab and unplugged the fuel pump.  I wanted to turn over the engine to circulate some oil since the engine sat for about 8 months dry.  A few hours prior I was testing the fuel system by running the pump with the engine off just to check for leaks, of which there were none!  Some extra pressure from the leak test shot some fuel into the engine while I was cranking for oil pressure and it sputtered a little bit.  At that time I knew it was gonna fire right up!  It was trying to with what little fuel that was in the rail!  After about 10 seconds of oil priming I plugged in the pump and turned the key.

First shot, sputter and die... OK, still some air in the fuel lines...
Second shot, VVRRRRRROOOOOOOOOOOOMMMMMMMMM!!!
I was so stoked that I just wailed on my horn for a few seconds!  All my supporting neigbors came out to give me the thumbs up!

Let me tell you, this car runs!  And it runs well!  The C-50 is a close-ratio gearbox designed to help the low torque 4A-GE accelerate. When you mate it to a GZE, it'll put out some respectable numbers! The C-50 redlines 2nd gear at 59 miles per hour, and with that SC pumping, it got there VERY fast. We're talking under 7 seconds, like 6.5-6.8. This car is definately a runner! It really puts the power down well, but if you're not careful, it'll smoke up the tires without breaking a sweat!

So I finish up by saying THANK YOU to all who offered me their advice and support. I COULD NOT have done it without all of the kind words and advice gven to me during the hardest times of the process. I owe it all to the wonderful MR2 community!

Here is the finished product!

 And my custom fuel selector switch and SC light:

Good luck to any who do this swap! It's not too difficult, just take your time and make dure you do it right! Working at a leisurely pace, I accomplished this in 7 days and 4 hours

Edited for formatting and content.

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