AE85 4age converstion ( FAQ THIS !! )

All the Frequently Asked Questions which are of a technical bent. Look here before posting a tech query.

Moderator: The Mod Squad

AE85 4age converstion ( FAQ THIS !! )

Postby AE85coupe » Thu May 25, 2006 9:23 pm

Hey a while back i wrote this for my mates website, i figured it would probably be useful as an FAQ, judging by the amounts of emails i get asking about this topic (probably full of spelling mistakes, and missing bits of info)

anyway here it is:

AE85 4age conversion guide

Note that this guide applies to a converstion involving a manual ae85 with a 16v 4age, if you plan on using a 20v or 4agze, you will need to make extra changes

Also note that AE70 corollas are in almost everyway the same as AE85's so this guide applies to them as well


For the engine use the orginal engine mounts from the 3a (they bolted straight onto the 4age)

The engine i had was from a front wheel drive 4age so i had the intake manifold cut with the ends swaped and welded (because the throttle is is on the opposite end in fwd's) if you get a rwd 4age, you will not have this problem (or a bigport 4age with rwd intake manifold)

If your engine is fwd, the water lines will need to be modified (cause fwd puts them in a bad spot) you can either use original 3a/rwd 4age lines and waterpump, or simply modify the fwd lines to suit

rwd extractors are needed and are easy to find, i used coby ones (to suit AE86)

you can use the original radiator from the 3a, but an electric fan is a good idea


for starters swap the rwd backing plate off the 3a engine onto the 4age

then get your hands on a 22 spline t50 with a ae86/te71/at141 (all 22 spline) driveshaft, or use whatever t50 you like, and get a driveshaft made to suit

i found i had trouble finding a cheap 4a bellhousing for the t50, so i modified a 5k bellhousing (came in lots of coronas) to fit the 4age (as it was the closest match to a 4a bellhousing) i simply drilled a couple of new holes and filed out the starter motor bolt holes slightly (of course if you have a 4a bellhousing its fine)

If the t50 you have isn't from and AE86, then the gearbox mount will not fit the AE85, you can either try find an AE86 mount, or simply pull the one off your old k50 (just the metal part, not the entire mount) and drill two new holes in it to mount it to the t50 box, works a treat

the 4age starter motor will need to be used as i discovered the original 3a one was too crap to even turn over the 4age (even after a rebuild on the starter) any 4age starter will fit though

for the clutch set up head to repco etc. and buy an AE86 slave and master cylinder, which cost about $100

the original manual pedal box should already have a wee hole about half way down the clutch pedal which the master cylinder piston fit into, line up where this hole is then drill though the firewall to mount the master cylinder (sits just behind the intake manifold, with the top about level with the top of the manifold)

(just as a note any rack and pinion steering rwd dx corrolla will have exactly the same pedal box as an ae85 or ae86 if your stuck trying to find one)

there are two bolts in which to mount the slave cylinder on next to the hole for the clutch fork, i simply ran hydarulic line from there to the master cylinder (used a flare set to put on the proper fittings which i pulled out of a honda along with some bendy rubber line so that it can flex when the engine/gearbox moves)

the slave cylinder can be mounted on either the right or the left hand side depending on the bellhousing you get (some are drivers some are passengers side, the AE86 originally had it on the drivers side)

it doesn't really matter which side the slave is on, its just a matter of running the line to the master cylinder

If your can't be bothered/can't afford a t50 set-up, the original k50 can be used (mine lasted for 8 months or so before i wrecked it) simply use a 4age pressure plate and 4age flywheel with a 3a clutch plate (this is because the k50 spline won't fit any other clutch plate) you will have no problems with the clutch slipping whatsover (contrary to what some believe may happen) in some cases the k50 bellhousing won't fit over the 4age flywheel due to a wee lump in the bellhousing, to fix this this, crack out a grinder and grind that lump down, also often the thrust bearing will not come foward far enough to engage the clutch, to fix this get a spacer put behind the bearing. Also a k50 driveshaft will fit an AE86 diff if without any problems


The standard diff will not hold up to the 4age unless you are very very nice to it (i blew mine with the old 3a)

So its a good idea to try find a complete AE86 diff setup as these will bolt straight in without modification (by complete i mean from disc to disc) sometimes its easier to find a TE71 diff which is exactly the same except the brake calipers, which are marginally different

If your to poor for an AE86/TE71 diff you can also go grab a diff from a T series corona, as these will also bolt right in and are just as strong as ae86 items but with no disc brakes, you will need to use an Ae86/te71 panhard rod thought..becuase corona ones are shorter, you can always get the corona one lengthed or buy and aftermarket one as there are plenty available.

I have heard also of people using diffs from ma61/ta61 celicas with success as well (these have larger discs and a shorter panhard rod if i remember correctly)

as an extra note, TE71 and t series Corona diffs will also accomodate aftermarket lsds (TRD etc.) for AE86's

Fuel System:

The original 3a fuel lines are not big enough to accomodate the fuel a 4age will need, also you will need a decent electric fuel pump

all i did for the fuel lines was get some 10ml glavanised steel pipe and run it from the tank to the engine (had an engineer bend it up for me as i discovered its dam hard to do without good tools, have seen it bent around people knees though)

you can use any decent inline fuel pump (vl commodore is a good option)

The original fuel tank has no baffling at all, so if you have less than 1/4 of a tank of gas and go round a corner to hard it will slosh and you will get some major fuel surge, you can either just make sure you always have lots of gas, or use an AE86 fuel tank (which is baffled) or if you really want (as i did) use two fuel pumps (one lift pump, one for the engine) with a surge tank does the trick nicely (even genuine AE86 tanks are known for getting alot of surge, if you thrash them round corners)


I'm not very knowledgeable on the complete aspects of wiring, but i suggest buying a ready to wire loom off trademe, or someone on toyspeed, then getting someone who knows something about car wiring to help you install it

or if you want you can always run carbs...


The standard AE85 brakes aren't to bad and can be used, but if your looking for an upgrade, complete ae86 front struts will bolt straight in giving you vented discs

Or you can go for even bigger brakes from TA63/TA61 celicas, once again the complete strut will bolt straight in, providing you use the celcia steering arm and the AE85 top hat/spring, the problem is these struts tend to give bad camber and it is best to invest in some adjustable camber plates if you go this way.

As for the rear brakes, TE71/AE86 diff comes with disc brakes attached, these are fairly good too.


You will probably want to upgrade your suspension as well, becuase dirty old AE85 suspension just isn't up to the play, some good springs and shocks will do the trick nicely

extra notes:

Pretty much everything above an be applied to KE70 corrollas as well, its just a matter of finding an AE70 engine crossmember/ k50 box and throwing them into your kE70 then you have yourself everything extra you need.
Last edited by AE85coupe on Thu May 25, 2006 9:28 pm, edited 1 time in total.
AE85 Trueno *For sale*
User avatar
Toyspeed Member
Posts: 1651
Joined: Thu Mar 06, 2003 6:48 pm
Location: Dunedin

Postby Bling » Thu May 25, 2006 9:27 pm

far out i'm impressed!! very detailed! 8)

User avatar
** Moderator **
Posts: 15989
Joined: Mon Dec 22, 2003 9:02 pm
Location: Quake City

Postby AE85coupe » Thu May 25, 2006 9:30 pm

yeah i can guarantee there is poor grammar and bad spelling all through this though haha, so yeah mods, if you find any, feel free to fix them
AE85 Trueno *For sale*
User avatar
Toyspeed Member
Posts: 1651
Joined: Thu Mar 06, 2003 6:48 pm
Location: Dunedin

Postby AE85coupe » Thu May 25, 2006 9:32 pm

oh yeah and if you think i've missed something, or have some extra questions, PM me
AE85 Trueno *For sale*
User avatar
Toyspeed Member
Posts: 1651
Joined: Thu Mar 06, 2003 6:48 pm
Location: Dunedin

Postby Meadzy » Thu May 25, 2006 11:00 pm

awesome man, i agree FAQ it, otherwise ill lose it when I come to do mine
"Keeping it true to the JDM"
J-Spec Group
User avatar
Toyspeed Member
Posts: 734
Joined: Tue Jul 19, 2005 8:29 pm
Location: Pukekohe (Driftland)

Postby Dell'Orto » Thu May 25, 2006 11:20 pm

User avatar
** Moderator **
Posts: 17488
Joined: Tue Jul 08, 2003 5:07 am
Location: Straight out the ghetto, Lower Hutt

Return to Technical FAQs - General

Who is online

Users browsing this forum: No registered users and 0 guests

Fatal: Not able to open ./cache/data_global.php