4A-GE conversion from 4A-C or 3A-C

and more on 20V installation...

There are many who have trouble finding true 4A-GE equipped AE86's in the USA and increasingly even, in Japan and elsewhere.  I have been asked a few hundred times "where can I find a GTS?" or How do I convert a SR5 to GTS???"  True in the USA the SR5 sold in great numbers and outnumbers the GTS 9 to 1.  The Japanese equivalent of the GTS is the GT-APEX, GT, and GTV models as opposed to 3A-C powered GL, SE, SR, XL, Lime and XL-Lisse.

The GTS version is the USA model equipped with the 4A-GE engines and SR5 is missing the 4A-GE, perhaps the one of the primary things that stirs the soul of the AE86 driver.  There are other significant differences to these sibling cars but the one thing remains to be asked...

So comes the question... 

"Can the SR5 be converted to the GTS?"

THE ANSWER IS YES......  However.....

There are so many things to be replaced on the SR5 to fully be equivalent of the GTS models that it's most likely much more economical to just sell the SR5 and buy a GTS.  Reasons which may justify a swap and upgrade is in the following cases: 

So having said that, I will list some of the major differences in the order of mechanical significance.  Here are the listing for the differences in parts pertaining to the engine swapping.  So you can decide if you want to go through with it...

  1. 4A-GE engine (and all brackets to support peripheral equipment)

  2. Most peripherals such as A/C, P/S pumps and compressors

  3. Complete intake and exhaust runners and headers

  4. Fuel pump and lines

  5. Gasoline tank, evaporation and related items

  6. Clutch fork and fluid line locations and bell housing (GTS and SR5 has opposite side clutch fork and slave due to the differences in the exhaust runner location and is extremely important not to run fluid lines next to exhaust systems)

  7. Transmission is the same unit as the GTS (T50C), however the speedometer gear is different, and must be replaced to read correct speed on the cluster. (due to different final drive ratio)

  8. EFI computer triggers and sensors

    • AFM or MAP

    • Air Temp Sensor (MAP only)

    • distributor assembly (MAP and AFM based are different)

    • Igniter and Coils (different for AFM and MAP based)

    • EFI Computer (MAP or AFM specific)

    • House Harness and Engine Harness and related junction boxes

    • All relays and VSV triggers

    • peripheral VSV triggers

    • Battery terminals and fusible link terminals and fuse box

    • some of these can be ignored for carburetor use such as Weber Side-draft carburetors

  9. Ignition system

  10. Dash Cluster missing check engine (W) lamp

  11. Labor and Installation Professional who can proceed properly so as not to create more problems (cheap or un-skilled installer would render the 4A-GE less powerful and unbelievably unreliable.

  12. Oil cooler, block and lines

  13. Clutch and flywheel

Speedometer cable output gear

Now as for other items that are mechanically different from the GT-S (4A-GE equipped models):

  1. Differential carrier

  2. Differential gear, axles, hub assembly (need 4A-GE unit to utilize commonly available LSD)

  3. Rear disk brakes vs. drum and related lines and cables (except Japanese GT)

  4. Steering rack, knuckles, tie rods

  5. Propeller shaft

  6. Clutch fork, assembly, cables, lines, bell housing (as mentioned above)

  7. Front and rear suspension are different from factory in spec but can be interchanged (Not significant as most owners replace them with aftermarket systems anyway)

Body and trim differences:

  1. Seats, panels and trim

  2. Outside mirrors (some were equipped with power as on the GTS, while others were fixed manual units)

  3. Tags and Emblems (obviously...)

  4. Front bumper lower spoiler

  5. Fender protector on 86-87 models

  6. Trunk moldings on 86-87 2 door coupes

  7. Rear spoiler missing on 84-85 SR5 3 door hatchbacks

  8. Color variations inside and outside

  9. Body side moldings

  10. Number of spot welding in key frame members on 86-87 models

  11. ETS Cassette Radio player (Ok, not important at all)

  12. Rear Wipers, Power Windows, Sunroof only optional on GTS

  13. Auto Climate Control (Japan Only)

As you can see, even only considering to replace the mechanicals, there are so many necessary items that one would need a donor GTS model to obtain all parts in a short period of time and at reasonable price.  BUT, on the other hand, it is not to say that it is not possible.  Since the body frame and most mounting surfaces are generally the same, the conversion would be time consuming but not impossible or difficult compared to many automobile custom projects. 


In case of the 20V or the GZE...

Additionally, if you are converting to use other engines in the 4A family as 4A-GZE or 20V, all of the above applies plus the additional processes as normally is required to convert from the 16V 4A-GE.  In the case of 20V (5-Valve) 4A-GE, hammering of the firewall is still necessary and re-harnessing.  But at this time, to drop in a 16 V would be fairly close in expense to just install the 20V.  Therefore, it makes the 20V or Supercharger conversion more a realistic and convenient step to go simultaneous with this type of conversion.  Seems natural no?...with time and budget permitting...  I have done the exact thing recently with my AE86 #6.  The new Club4AG 2 door SR5 20V.

The reasoning behind it was that this SR5 was previously converted to GTS specs and needed a new engine, and additionally the installed roll cage was welded in place and did not justify replacement into another car.  This is also the car that was used by the 2 Japanese Pro-Drift drivers in the recent Speedtrial USA Drift Event held February 23rd 2002 at Buttonwillow, California.  It held up well and gave many a glimpse of what a SR5 can be...

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Before... (SR5 with some GTS body panels attached)

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After... (SR5 with complete paint and 20V installed)

Oil Pressure sending unit must be replaced from the 16V to the 20V in order for the AE86 Oil Pressure Gauge to operate properly (AE101 and AE111 are warning lamps only while AE86 has a analog needle gauge)

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Hammered out firewall for 20V installation

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Donor 20V Silvertop with 16V alternator attched for use on AE86.

More on loading 20V 4A-GE into AE86