1. Exhaust

-Silvertop

The complete 16v exhaust system can be used with the 20v silvertop. The only needed modification will be to the outermost flanges of the stock 16v header (pictures are of an ae86 header, but the bolt patern is the same)

The 20v header can also be used, but will require either a custom bpipe, or modifications to an existing 20v bpipe. The 20v silvertop header also has clearance issues with any exhaust side mounted starter. Clearance between the ST header and starter will only be a few millimeters.

The diameter of the 20v header pipes is identical to those on the 16v. The 20v header may have a slight advantage due to the use of theta plates, but dimensionally, the headers are the same or similar.

-Blacktop

The 16v header can also be used with the blacktop, but will result in power loss due to the Blacktop’s larger exhaust ports. A typical 16v header/manifold will be a bit constricting. 16v manifolds have been used with blacktops, so it is possible. Larger diameter 16v headers may be available.

For best results, use the blacktop header (or exhaust header that has the same exhaust port dimensions) when possible.

The exhaust mounted starter will not clear the larger diameter blacktop header. This will be an issue with any 1985-1987.5 20v conversions where the original c50 transmission is to be used since these transmissions lack the intake side mounting position. You really have 3 options in this situation.

a. Use the 16v setup, and take the performance hit
b. Use a later c52 transmission (or bellhousing) that does have the intake starter mounting position
c. Modify the 20v header to clear the starter.

Once again, a custom bpipe will have to be made, or an existing bpipe modified

Keep in mind that 87+ mr2’s used a larger diameter bpipe, cat, and muffler, so this is your best choice for the 20v. The 4agze equipped mr2’s used the same exhaust setup as the NA cars did.

2. Transmission

All mk1 mr2 transmission will physically bolt up to the 4age 20v. There are considerations you must make though.

-A series motors used 2 different sizes of flywheel. Early mr2’s, up till around 1986, used a 200mm flywheel. From 86 on, a 212mm flywheel was used. (200mm and 212mm pertains to the griping area of the flywheel. The actual diameter of the flywheels was the same). The 20v came with the later size flywheel, so when ordering a replacement clutch and pressureplate, just ask for a clutch kit for a 1989 mr2. If using the smaller flywheel, ask for a set from an 85 mr2. Either clutch set will be sufficient for the stock 4age 20v.
-Early c50 transmissions only had one mounting position for the starter. With this transmission, you are limited to mounting the starter on the exhaust side of the motor. These transmissions are on the 85-87.5 mr2’s. Later mr2’s had the c52 transmission. This transmission had a secondary starter mounting position on the intake side of the motor, just like the stock 20v transmissions. If you plan on using your 16v exhaust manifold, which is perfectly fine with a silvertop, you can mount the starter on either side. If you plan on using a 20v header, especially the blacktop’s, the header will not clear the exhaust mounted starter. If you must use the exhaust mounted starter in this case, the header will have to be modified for clearance.

-The c52 and c56 that comes with a 20v can also be used with modification and transferring a few parts from the original mr2 transmission, namely your mr2 selector shaft, and the entire mr2 shifter assembly. On the silvertop c52, a hole will have to be drilled for the selector shaft and the oil seal. On the C56 however, there is no casting for the oil seal. One of 3 approaches has to be taken.
-Add the additional aluminum casting, and drill as you normally would
-Fab an adapter or a makeshift casting (this has been done with JB weld, not the ideal way, but seems to be holding up in this case)
-Reuse the center transmission casing from your original mr2 transmission. This requires taking both transmissions apart

Here are some pics of the problem area:

-6speed transmissions are available for the 20v, known as the c60. Some blacktops came with a 6speed stock, although it was not a real common option. The same considerations must be made for the oil seal casting that have to be made when using a blacktop c56 5 speed. Getting a blacktop with a 6speed is usually somewhat pricey.
One other option is to use a 00+ Celica 6speed. The bellhousings are different, but can be swapped somewhat easily. All that holds the bellhousing to the central casing are the external 12mm bolts, and two 12mm bolts on the inside of the bellhousing that are attached to a reverse lockout arm. Once the external bolts are removed, the internal ones can be removed and installed through the 1-2 inch resulting gap. It’s a little bit tricky, but is much easier than taking the transmission apart. Once apart, remove the old differential bearing races and shims from the 4age bellhousing and replace them with the ones from the original 6speed bellhousing. It is very important that the differential stay with all of its original races and shims. This is the only way to keep the tension on the differential somewhat within spec. Too much or too little tension, and you will burn your differential bearings.

The celica 6speed will also require the use of 1991+ mr2 NA axles. No drilling is required since the Celica’s selector shaft is already on the correct side of the motor. Just add the mr2 selector shaft and shift assembly.

3. Cooling

The 20v does require hoses to be run differently. It is very straight forward, and one of the easiest parts of the swap. Rather than draw up a detailed explanation, here are some detailed pictures:

The rule of thumb that I use is link the driver’s side hard line that runs under the center of the car to the driver’s side water outlet on the 20v motor. Same for the passenger side. The passenger side hardline (the one with the oil cooler) goes to the water inlet on the back of the head next to the exhaust manifold. I usually try to incorporate my filler neck into this side of the cooling system. The needed hose stock can be purchased at Napa along with any flexible hoses you might want to use.

The heater hoses are also very straight forward. The 16v hoses can be used, but it is better just to buy the correct diameter tubing, and simply cut new hoses to length.

4. Throttle cable

My preferred method for dealing with the 16v cable being too short for the 20v is to simply reroute it. I drill a second hole in the fire wall about 6inches to the passenger side of the original throttle cable hole (be careful not to hit anything under the dash when you do this). I then route the cable under the dash, under the center console, behind the rear firewall and out the trunk release cable hole in the rear firewall (if you want to keep your trunk release, a second hole can be drilled). This puts the throttle cable in the perfect position with more than enough length.

5. Wiring

This is the heart of this conversion. Many 20v swaps have failed due to installers being unable to master the wiring. To make this part of the swap go more smoothly, I offer a complete plug and play solution. Here is a picture of the finished product:

It is perfectly fitted for the aw11. The air conditioning works along with the enginebay cooling fan. The 20v ecu will mount in the stock aw11 location. I test every harness on my own vehicle so that it is know to be operational and defect free before I ship it. The harness is loomed and ready to run.

The whole concept is to offer a harness that looks and fits like it was oem. Its as if you went to the Toyota dealership and ordered a stock harness, although my harness is cheaper than a dealership replacement harness. The cost is $350 and has a 100% success rate.

It’s a superior product compared to other offerings on the internet that claim to be plug and play. Competitive offerings ship mostly unloomed (ie you get a barewire harness), totally untested and have been known to contain defects. You as the end user get to sort through all the issues. Far from a hook it up in 20 minutes and turn the key proposition.

If you decide to do the wiring yourself, it is best to get an uncut 20v harness. There will be plenty to modify and change to make it work with the aw11 bodyharness, but is much easier than trying to get a cut harness to work. With a typical cut harness, you end up reconstructing a good portion of the harness. Not good if you are not pretty advanced at automotive wiring. Either way, there is a lot of soldering involved.

Here is a link to a good step by step on how to get an uncut 20v harness to work in the aw11.

http://www.padandwheels.com/mr2/blac…ng/wiring.html

Swapping a 20v 4age for a 16v 4age has become a very common practice. Aside from significant performance advantages, you will be getting a newer engine typically with much lower mileage. Parts availability for the 20v has improved over the years as well. There are a number of Toyota dealerships that specialize in JDM parts. Champion Toyota comes to mind. Almost all the parts can be purchased easily and are priced like normal USDM dealership replacement parts. Considering many mr2 replacement parts have to be ordered anyway, getting 20v parts is not much more of a hassle.

The 20v conversion is a fairly easy bolt-in swap. Perfect for those looking for a high revving engine with a wonderfully broad powerband who also want stock reliability.

So, this is pretty much in line with what Toyota said for the 20V blacktop, 165hp at the flywheel: (1 – 137/165) * 100% = ~17% drivetrain loss. Which is about right for the AW11 drivetrain.

Instead of trying to find rubber hose of the exact shape, I purchased some 1-1/4″ 0D 6061 Aluminum pipe from a local supplier for the straight runs. It was cheap and very easy to work with.

The engine-radiator line was easy to fabricate. If you notice closely I reused a line from the 16V engine as well as one from the 20V clip.

The radiator-engine line was more complicated since I needed to incorporate the filler neck. Also, I am not using the stock MR2 oil cooler, so I don’t need to route the line over the exhaust manifold. (if you do use the oil cooler, just mount the filler neck over the manifold.) I ran the line over to the driver’s side of the car, straight up to near the fuse box and then back over into the thermostat housing. For the elbows I just purchased 2 proper sized hoses that each had two 90 degree bends. Then just made up some brackets to hold the pipe to the firewall. I attached the filler neck to the firewall as well.

The heater core lines are a lot easier since you just use flexible rubber hose. I forget the diameter I used, but it’s the same as the 16V lines. I used the same bracket that was on the tranny to hold the lines in place. You can sorta make them out in the below pic:

Fuel line

Contrary to what was previously on this page, the 16V fuel line fits fine with no modifications (both SC & NA). I mistakenly used the 20V line which needed to be extended. Sorry about that.
 

Throttle Cable

For neatness this needs to be extended a couple feet. If not, the cable will have to drape over the engine. I combined the MR2 cable with that of the 20V.

Here’s the steps and pics:

- Cut the ends of each off with pliers, being careful not to cut the actual cable.
- Strip the protective rubber about 1/2″ back exposing the metal structure of the cable housing.
- Measure/mark the length of cable needed for when your foot is off the gas pedal & when it’s all the way down. Do the same on the extension end, this time using the actual throttle assembly. If you need to expose more cable on either side, cut off more of the housing.
- Once you get the lengths right, using a 1/16″ ferrule (you may need to enlarge the hole to allow both cables to fit), crimp the 2 cables together.
- Using some 5/16″ ID fuel hose I had sitting around, that acts as a protective covering for the exposed cable/ferrule. Make sure the crimped ferrule can slide through it easy enough.
- Use some heat shrink tubing on the ends of the joint to keep moisture & dirt out.
- Then some clamps to hold the hose onto the metal housing

Alternator Bracket

The 20V has a huge alternator bracket with an idler pulley so that the belt doesn’t interfere with the chassis. You can reuse the 16V NA bracket on the 20V block. However, on the blacktop you will need to cut away some material to clear the hydraulic timing belt tensioner.

Before:

After:

Oil Pressure Sender

Use the 16V oil pressure sensor, as the Trueno/Levins just have an idiot light instead of a gauge.

Clutch/Flywheel Info

If you are replacing the clutch or flywheel make sure to get one for a C series transmission. The MR2 SC clutch/flywheel will NOT fit. The shaft on the C series trannies are smaller than the E series.

Mounting (ECU, MAP, Ignitor/Coil, Coolant Overflow Bottle)

Fab mounts for the ECU in the new driver’s side location.

For the blacktop, mount the MAP sensor at a convenient location near the #1 intake side. I used an existing welded nut on the chassis.

Same goes with the ignitor & coil, but this time near #4. I chose a place on the strut tower. 2 bolts fit perfectly in existing holes. A third hole was drilled and tapped.

Since the filler neck was on the opposite side of the engine bay, I had to use a different location for the overflow bottle. I decided to use a different bottle altogether since mine was weathered pretty bad. Just using a cheapo from Autozone at the moment.

Vaccuum Lines

The 20V has 2 brake booster lines coming off the TBs. Luckily both are on the #1 side of the engine, making it easy to route the hose to the MR2′s single booster line. I used the one that comes of the #4 TB, since the #1′s fitting can be easily removed and a bolt inserted to block it off.

You can also block of a line that was used for the power steering system in the Levin/Trueno. Near the fuel rail by #4 cylinder there should be 3 hoses, each of distinct sizes. It’s the middle sized hose that can be capped.

Crank Pulley

If you have the Silvertop, make sure to use the 16V crank pulley and timing marker. This helps with adjusting the ignition timing. On the blacktop, you can’t use the 16V timing marker since it uses a different tensioner. However, make sure to paint marks along the crank pulley, on all edges. The belt gets in the way of the inside mark making it hard to see.

Decklid Latch

The intake box on the Blacktop interferes with the engine latch. So grind away at the latch until there’s room. I had to bend one side of the latch slightly, as well as remove the bottom bolt hole to make room for the coupling to the air filter.

Axles & Tranny Stiffener

The Levins and Truenos have equal length drive shafts. Unfortunately these shafts are an inch or 2 too long to use in the MR2. The MR2 axles fit fine of course, so it may be possible to Frankenstein something together. The cup of the 20V extension shaft on the passenger side is too large for the MR2′s tulip joints. You may be able to remove the tulip joint from the 20V axle and refit it to the MR2′s axle. I’m not sure. This is something I may try later, as I have a spare driver’s side MR2 axle.

Also, if you use the MR2 axles, the 20V tranny stiffener will not fit. You can either grind away some of the material to make the stiffener fit, or just run without it. To make it fit I believe you need to chop 1 corner off, using one less bolt holding it in place.

I took my time with the wiring, basically working on it throughout the mechanical part of the swap. Since it doesn’t involve any real physical dirty work, I worked on it when I wanted to take a break from those sort of things. Plus once I got the wiring harness mapped out on paper, I could do all the work inside the AC’d house.

1. The first step is to label each connector as you remove it from the engine.
2. Once you get the harness out of the engine, start taking notes on each connector. Include the orientation of the pinout and the wire colors. Make sure to keep some space between the difference pins, as you will be making more notes here shortly.
3. Next, start taking apart the harness, removing all the tape and wire loom. Make sure to keep the harness organized and untangled, as well as in it’s original layout. Once you have the original loom & tape off of a section, loop a piece of electrical tape around the wires. A loop of tape every 12-18 inches will keep everything from getting tangled. Also, make sure to keep the wire loom so that you can reuse it once you get the loom completed.
4. When this is done, begin mapping out each and every wire. This is where most of the time is spent, but it is very important in getting to know the wiring harness. It also makes removing unneeded accessories a breeze. If you did not get a clip or half cut, this is going to make this sorta difficult, as there are quite a few wires that will just terminate at the body harness connectors. Most of these are the instrument cluster, AC, ABS, and ignition switch signals. A couple of them are for the idle-up circuitry as well. If you do have a clip, trace these pins at the body harness connectors if you can’t figure out which signals they are by where they terminate on the engine harness. There’s no need to torture yourself and map out the entire body harness. Unless you really want to. Though it is nice having the body harness stripped so that you can use it for spare wire and pins.
5. Now, start removing these unneeded circuits. These circuits won’t have all their wires on exclusive connectors. So you will need to remove some pins/wires from other needed connectors. To do this, you need something with a very tiny point. I just used a safety pin the whole time. On the late style Toyota connectors, there is usually a lock on them that you need to raise. See the white rectangular area on the connector below? Pry up on the two indented spaces with the safety pin and the lock should raise up. Do NOT attempt to remove the lock entirely from the connector. Not only is it unnecessary, but you could also destroy the lock.

   Once it is in the up position you can remove the pins by releasing the tab that is holding the individual pins inside. Look at the front of the connector and you should easily see the tab that you need to push down. While pushing down with the safety pin, pull the wire out from the back of the connector. For the older style Toyota connectors (what is on the MKI MR2) this is the only thing holding the pins inside the connectors. There is no lock.

   

   The circuits I removed from the 20V engine harness were the ABS, headlights, radiator fans, horns, and AC. Now’s the time to decide whether or not you will want to use AC.

6. After that is done, set the 20V harness aside and begin work on the MR2 harness. I also removed the body harness from the MR2, which made it easier to trace wires back into the fuse box (the engine fuse box is on the body harness of the MR2, engine harness of the 20V). I also needed to run more wires to the MR2s body harness for the Blacktop, more on that later.
7. No need to label every connector on the MR2. Only the main ones that you will reuse, the trunk connector, the grey connectors in the engine bay, and the body harness connectors that interface to the MR2′s interior harness. Also, are you going to use the MR2′s engine bay fan? If so, make sure to label those.
8. Once removed, begin stripping the old tape and loom from the MR2 harnesses. Try your best to keep the firewall grommets intact. I ended up slicing them down the middle to remove them from the harness. This worked farily well.
9. If you are going to use the engine bay fan, remove that circuit. It’s very straightforward. Now, start mapping out the wires that interface between the body and engine harness. Use the wiring diagrams in the BGB and/or Haynes manual to help. There may be some discrepancies within the documentation so be sure to check the circuits by hand just in case.
10. By now, you should understand what all you need to do to join the 20V engine harness to the MR2 body harness. Here’s a diagram that will hopefully help you out, that I put together after the swap (click on it for larger pic). This is the Blacktop wiring diagram drawn in the form of Toyota’s MR2 diagrams. The red lines indicate that it is part of the engine harness, and the black is the MR2′s body harness. So…wherever black meets red is a signal that you will need to pull to your connector interface.
    • The Silvertop harness will be slightly different, at least with the COR. The Alternator Sensing fuse is optional. You could just tie this to B if you wish.
    • Notice how I wired the engine bay fan as well. This way it’s on whenever the ignition is in the ON position. You could wire it up like the 16V MR2 with the temp sensor and the computer if you wish. Just takes a couple more wires and mounting of the sensor in the engine bay.
    • The 2 Battery+ were connected together on the other side of the connector and were part of the alternator & starter wiring direct from the battery. This is taken care of by the battery relocation wiring that I did, where I wired directly from the battery to the starter and alternator.
    • The other 2 were moved to the trunk connector



However, these are not the only signals needed to complete the interface. There are a few other wires on the body harnesses needed for the ECU. Below is a diagram of all the ECU signals. Those in blue indicate signals contained the above wire diagram. TC1 and TC2 are the two trunck connectors I used to complete the interface. So those in black that go to TC1 and TC2 will need to be in the interface as well.



I used the original trunk connector that was on the MR2 harness and an additional connector I grabbed from the 20V body-engine harness interface. I was able to eliminate both engine bay grey connectors on the original MR2 body harness which makes things a little neater in the engine bay. It may be possible to use only one connector, especially if you are doing a silvertop swap.

New Connector Diagrams

Here are pin description tables of the 2 connectors I used. By no means is this the only way to do this, it just is here to give you an idea of the signals you will need to run:

Update (Feb 14, 2008): I changed the first connector around a bit to keep this with what I’m actually currently using. When I shortened the harnesses in the trunk a year or so ago, I moved the 4 ELS signals to the second connector to reduce the number of contacts in this main connector. It was becoming too hard to detach/reattach the connector. I’ve also added the 2nd connector diagram as well as the stock 16V connector diagrams.

New 20V Trunk Connector #1:



	Body Harness (Male) Side		Engine Harness (Female) Side
1	G/W	Check Engine Light to Dash	R/Y	Check Engine Light from ECU
2	Y/Blk	Oil Pressure to Driver’s seat connector	W	Oil Pressure Sensor
3	R/W	Batt from EFI Fuse	R/W	Batt to ECU
4	NC		NC
5	Blk	Starter Relay	Blk	Terminal 50 on Starter
6	Y/G	Water Temp Gauge to Driver’s seat connector	Y/G	Water Temp Sensor
7	Blk	+B EFI Relay	Blk	+B COR, ECU, O2 Sensor, etc
8	Blk/Y	10A Engine Fuse	R/Blu	Alternator IG signal
9	NC		NC
10	Purp/W	Speed Sensor to Driver’s seat connector	Purp/W	ECU Speed Sensor input
11	R/Blk	L&R Reverse Lights	R/Blk	Reverse Switch on Tranny
12	Blk/R	Power from Ignition Main Relay	Blk/W	Ignitor/Coil & Injectors
13		Cooling Fan Relay coil side	LG/Blk	CF from ECU
14	NC		NC
15	Blk	IG- to Tachometer to Driver’s seat connector	Blk	IG- from Ignitor/Coil & Diagnosis
16	W	Alt ‘S’ 5A fuse (added to fuse/relay box)	W	Alt ‘S’ Signal
17	Y	5A Charge ‘L’ Signal from Alternator	Y	‘L’ Signal from Alternator
18	Blu	Fuel Pump	Blu/Blk	Circuit Opening Relay & Diagnosis
19	NC		NC
20	Blk/G	Engine Bay Fan	Blk/G	Engine Bay Fan
21	Blu/W	Engine Bay Fan	Blu/W	Engine Bay Fan
22	Blu/Blk	Engine Bay Fan	Blu/Blk	Engine Bay Fan

Optional

Here’s just another way at looking at the connector pin descriptions (click to zoom in):



Blue = Body Harness side
Red = Engine Harness side
* = there’s 2 ways to do this. I wired the engine bay fan to be on whenever the ignition is on. If you would like to keep the original wiring with the cooling fan computer and the temp sensor, just use the 2 empty spaces for the other 2 wires (Blk/G & Blu/W) in the circuit.

New 20V Trunk Connector #2:

The second connector contains the STA signal, a ground, the idle-up signals, and some optional things I wired in (air/fuel meter and a VVT light in my dash (which i need to fix, cause it’s still not wired right in my dash)).



	Body Harness (Male) Side		Engine Harness (Female) Side
1	NC		NC
2	W/Blk		W/Blk
3	Blu/R	Cooling Fan Relay switch side	W/Blu	ELS1 to ECU
4	Blu	Blower Relay	Blu	ELS2 to ECU
5	Blk/W	Starter Relay	Blk/W	ECU STA
6	NC		NC
7	–	A/F Meter Ground	–	O2 Sensor Ground
8	G	Taillight Relay	G	ELS3 to ECU
9	Blk	Defog Switch	Blk	ELS4 to ECU
10	R	Dash	R	ECU VVT
11	NC		NC
12	–	A/F Meter Signal	–	O2 Sensor Signal

Optional



Blue = Body Harness side
Red = Engine Harness side

Old 16V Connectors

I’ve gotten some emails in the past to document the stock 16V connectors. These vary by year, but here’s what I had on my ’85:

Stock 16V 4-pin Grey Connector in the engine bay:

Battery + Various Big Fuses Battery, Alt, Starter Black	Battery + Various Big Fuses Battery, Alt, Starter W
Engine Bay Fan Power Fan Relay Engine Bay Fan Blue/Black	Term50 Starter Relay Terminal 50 on Starter Black/W

Stock 16V 12-pin Grey Connector in engine bay:

Engine Bay Fan NC Engine Bay Fan Blue/W	–	Clutch Start Switch Driver’s side kick panel Back to starter relay pin Black/W
AC Clutch AC Clutch Fuse ECU Black/W	–	–
–	–	Starter Relay Starter Relay Back to clutch start switch pin Black
–	CEL Gauge cluster ECU G/W	–

• The AC wiring was removed since I ripped out the air conditioning system.
• Same with this engine bay fan wire, since I didn’t use the temp sensor.
• The clutch start switch and starter relay were tied together on the engine harness side. So i just soldered these connections together on the body harness side.
• CEL was moved to trunk connector.

So, to summarize with these 2 connectors: Only 3 of these wires were rerouted to the new trunk connector. The rest were either tied together, used by my new battery wiring, or discarded.

Stock 16V 22-pin Trunk Connector:Here’s the stock 16V trunk connector. The green shows the pins that weren’t moved when redoing the connector for the swap. I tried to keep it the same as much as possible.

	Body Harness (Male) Side		Engine Harness (Female) Side
1	NC		NC
2	Y/Blk	Oil Pressure to Driver’s seat connector	Y/Blk	Oil Pressure Sensor
3	NC		NC
4	NC		Blk	Injector #3 & 4
5	NC		R	Injector #1 & 2
6	Y/G		Y/G	Temp sensor
7	Blk	EFI Relay +B	Black	COR +B
8	Blk/Y	10A Engine Fuse	Blk/Y	Alternator
9	NC		NC
10	Purp/W	Speed Sensor to Driver’s seat connector	Purp/W	ECU Speed Sensor input
11	R/Blk	L&R Taillights	NC
12	Blk/R	Engine main relay&fuses	Blk/R	Ignitor/Coil
13	W/R	7.5A AM2	W/R	ECU
14	NC		NC
15	Blk	IG- to Tachometer to Driver’s seat connector	Blk	IG- from Ignitor/Coil & Diagnosis
16	NC		NC
17	Y	5A Charge fuse	Y	Alternator
18	Blu	Fuel Pump	Blu	#1 COR
19	NC		NC
20	Blk/G	Engine Bay Fan	NC
21	W/Blk	L&R Tail Lights	Br	Chassis Ground
22	Blk	Idle up diodes	Black	ECU ISC

Same as resulting connector after swap

Using the 20V Manifold

First of all, if you are reusing a C50 transmission you must use the 16V manifold as the 20V header will interfere with the starter. (Actually, someone just got done with his swap and says that the 20V header fits fine when using the starter on the exhaust side. So, YMMV.) If you have a C52 that has starter humps on both intake and exhaust sides you will need to move the starter to the intake side. I’ll leave the relocating exercise to you, as I don’t have much experience with it. However, I would recommend just using the C56 tranny as it is better geared for the high 20V powerband.

At any rate, you need to mate the 20V header with the MR2′s exhaust system. If you currently have a nice exhaust and don’t plan on replacing it, you will need to either extend your current downpipe to reach the header, or you will need to extend the header down to reach the downpipe. I believe there’s about a 2″ difference that needs to be made up. You will also need a custom flange to mate with the header. If you purchased a front clip, just use the flange off the downpipe.

I was building a whole new exhaust at the time, so I just reused the 20V downpipe and built the rest of the exhaust system off of it. The 20V downpipe is nice because it has a flexjoint in it, so that I didn’t have to incorporate a typical flexpipe. Here’s pics of my finished exhaust.

Using the 16V Manifold

If you use the 16V manifold (stock or a TRD) you will need to expand the ‘ears’ of the flange. Here’s pics courtesy of Dave Spinetti from his web page.

Ears cut off, notice the gap needed to be filled:

Complete:

If you sit the stock C50/52 next to the C56, you can easily see what needs to be done to the new tranny. The red circled area is a point of concern on the newer C56s (Blacktop). It doesn’t have a ‘flange’ at the end of the gear selector shaft housing. None of the Silvertop C56s are known to be like this. It will take a bit of machining to do this job correctly. If this part of your C56 looks like the C52, the conversion will be much simpler.

C50/C52 MR2	C56 Silvertop	C56 Blacktop

In either case, you will need to purchase a new selector shaft oil seal from Toyota. I forget how much it was, but was under $10 I’m sure.

Part #: 90311-15003

1) Start by removing the slave cylinder lines and brackets, as well as the engine mounts on both transmissions. Remove the gear selector linkage mounted to the trannies.

2) Now have the tranny in the neutral position. Twist the shaft into the middle position and push or pull it to the middle position.

On the C52, Remove the four 14mm bolts holding the end plate in place (red). Also remove the 14mm bolt that aligns the shaft (blue). Pull out the end plate, you will be reusing it on the C56.

On the C56, Remove the four 14mm bolts holding the shaft in place. As well as the bolt on top of the housing. These bolts are in the same place as the above pictured C52. Slide the selector shaft out. The C56 is now ready for the conversion.

3) Now, on the C52 remove the 12mm nut on the pin holding the lever to the shaft. Take a hammer to the end of the pin to nudge it out. Remove the dust boot from the tranny oil seal. Then the handle should easily come off the shaft.

4) Now, push the shaft out toward the endplate side. May need a nudge from the palm of your hand. You will be reusing this shaft in the C56.

5) In order for the shaft to fit through the C56 you need to drill a hole on the opposite end of the shaft housing. Measure the proper point to drill the hole.

Here’s what it looks like on the Blacktop C56:

Here’s the Silvertop C56:

6) Drill a pilot hole with a small drill bit. Make sure to be parallel with the shaft housing. Turn the tranny so that the housing is on the bottom. This insures that few shavings will enter the transmission gears. You may also want to stuff something inside the other end to collect any other shavings.

7) For the older C56 transmission, increase the size of the hole so that the new oil seal can be pressed in. I’m not sure of it’s size, so you’ll need to measure it yourself. The seal is a press fit, so make sure the size of the hole is smaller than the seal. Tap the seal in place with a mallet making sure it goes in square.

Clean up as much of the fillings inside the housing as you can. Goto Step 10.

For the newer C56, increase your bit size until the shaft fits. My selector shaft was just over 1/2″ wide. So I ended up using a 1/2″ bit and then a smaller one to ream it just a bit. Smooth with very fine grit sand paper. You will most likely need to make this hole larger later on, for the oil seal adapter that you need to make.

9) Here’s a diagram of a possible oil seal, courtesy of Bill Strong:

And here’s what mine ended up looking like after having a friend machine it out of SS stock. Go here for a lot more pics.

10) Once you have the seal pressed in, fit the shaft through the endplate side. It may take a little fidgeting to get the pieces on the shaft to line up properly with the forks inside. Slide the dust boot in place. Replace the lever and bolt and the endplate. Benchtest your new linkage and you are ready to put everything back on and remount the tranny.