SpeedTECH The definitve guide to EFI transplants


4AGE RWD Conversion: Engine Installation 

This page deals with the actual installation of 4AGEs in a rear wheel drive configuration. The methods proposed here are merely one way of achieving the required result; they are not necessarily the only way or even the best way. If you have a better or alternative solution I would like to hear about it and include it in here.

Page Contents 

Engine Mounts Alternator Mount PS and AC Radiator
Water Pump Sensor Block 20 Valve Plumbing Cambelts
#Oil Oil and Sumps Oil Drains Oil Coolers
Inlet Manifolds Air Filters Throttle Linkages Fuel System
Aftermarket ECUs Wiring Exhaust System

Engine Mounts 

Depending on the car it may be easiest to use the standard 4AGE RWD engine mounts. 3A RWD engine mounts (sourced from AE 85/KE 70 Corollas) are identical to 4A ones and so are a direct bolt on fit. A 4AGE will directly bolt into any car originally fitted with a 3A engine.

If you need to fabricate custom mounts then just use the block bosses that best fit the car the engine is going into. Be sure to use at least 3 and preferably 4 bosses on each side. The standard RWD set up uses 4 bosses around the oil filter, and 3 on the intake side in a similar location.

Alternator Mount 

The RWD alternator mount locates the unit low on the intake side of the engine, which may be of use if the FWD location is inconvenient, however, this is in the way of the supercharger on the 4AGZE. The FWD 4A SOHC and 4AFE narrow angle twin cam gear engine (and possibly the naturally aspirated MR2) mount the alternator high on the exhaust side.

On AE92 4AGE Corollas the alternator is mounted high on the intake side of the engine and the A/C and P/S are mounted on the exhaust side lower down.

Power Steering and Air Conditioning 

Some RWD AE86 Corollas and AA 63 Celicas were fitted with both air conditioning and power steering, so there are a variety of brackets available, however, they are not that common. The FWD supercharged engines mount the alternator, A/C and P/S all on the exhaust side, as the supercharger occupies the intake side.

Oil and Sumps 

Most RWD transplants mount the engine upright as opposed to the slight angle it sits on in the FWD set up. Note that a factory RWD installation has the engine on a slight angle too. The engine is on the original angle when the base of the sump is almost horizontal. Mounting the engine so it is vertical does not effect the oil delivery, however, the majority of people installing the engines into Lotus Seven type sports cars also shorten the sump. They tend to chop the sump off level on the ‘high’ side which takes about 30 mm out the ‘low side’. Provided the oil pickup is modified in the same manner there are generally no problems. 

My sump has been shortened as above and I run my engine oil level about 5mm above the ‘full’ mark on the dipstick and in 120,000 km have not had any problems. Fitting a 3mm steel ‘bash cap’ to the bottom and front of the sump is wise in low cars. I have about 3 inches of sump ground clearance - and the bash cap has taken chunks out of the road on many occasions. 

The mid 1989 onwards engine pistons are oil cooled via little jets aimed up the bores. These engines have a higher capacity oil pump to make up for the increased demand. 


A word or two about oil. I am a strong advocate of synthetic oil. The idea is that altho’ your engine is not new the use of synthetic will prevent the engine from wearing much more than it has already when you get it. Also a friend who worked for an oil company pointed out to me years ago it is silly to scrimp on oil by buying the 10 buck special and changing it every 10,000 km when you go thru a hundred times that cost worth of petrol in that time.....

Also an engine transplant or rebuild because you used crap oil costs a lot more than a few oil changes using high quality oil......

I use Mobil 1 (no sponsorship!) because I can buy it anywhere if I need to. My 20 valve eats about 1 litre of oil every 5000 km.

Oil Drains 

The 16 Valve engines have a tendency at high RPM to top the head up with oil. On the earlier engines this can result in oil getting into the intake manifold via the cam cover breather and turning the motor into a 2-stroke, especially if you are cornering at the time. Not a good look, trust me. I thought I had killed it.

Some cars also have oil surge in this state with attendant drop off in oil pressure. I stress that this tends to occur in race applications only. This can still occur with the ‘Red Top’ motor despite the external oil drain. Most people solve the problem by fitting an external catch tank with a drain back to the sump, with the intake breather taking suction from this catch tank.

The 20 Valve has very large oil drains and does not suffer from this problem.

Oil Coolers 

Some 4AGEs come with a factory oil cooler. This is a thermostatic bypass type with the oil being cooled diverted from the engine oil system to the oil cooler and then returning directly to the sump via an external fitting. This is in contrast to aftermarket sandwich plates that are either thermostatic bypass or full flow and divert oil from the oil filter to the oil cooler prior to going through the engine oil galleries.

European and some Japanese AE 86 cars have the factory oil cooler sandwich plates as do 1988-1991 AE 92 US Toyota Corolla GT-S. To use the factory set up on another car you need the oil pan/sump (unless you modify one to take a return fitting), the sandwich plate that bolts on between the oil filter and block, and the oil cooler core. Some MR2s have an oil cooler also, however, they use radiator water for cooling via an in-line heat exchanger as opposed to a radiator. The sandwich plates and sumps are identical.

Fitting an aftermarket thermostatic sandwich plate and oil cooler in my 20 Valve Lotus Seven Replica reduced the radiator water temperature by ½ on the gauge, ie previously the gauge sat at ½, and now it sits on ¼. 

Factory sumps are relatively cheap to buy from Toyota (about 60 bucks) should you need to replace yours. If you are fitting the engine into a car where the sump bowl is at the wrong end then just bolt the sump to a sturdy steel plate or a thick piece of wood and cut it off at a suitable height up the side. Turn the chopped portion around and bash/fabricate it until it lines up then weld it back together. Be careful when modifying the oil pick up: it needs to sit in a similar position at the other end of the engine with nice smooth bends in the suction pipe work.


By all accounts if a cambelt fails on any 4AGE the valves still do not hit the pistons, however, it is obviously wise to change the belt when you get the engine. Change the belt every 100,000 km, or sooner if you give the engine a hard time. I once bought an AE 86 with several teeth missing from the cambelt, and it still went like a rocket...

Cambelts are fairly cheap if you go to the right places - I got one for about 40% the cost of the Toyota part by going to a general auto pats distributor. Remember, belts are like timing chains in that they are all the same basic design and it is just the lengths vary. The 20 Valve belt is 2 teeth shorter than the 16 Valve belt as the cams are closer together due to the valve angle being less. When I got one from a general auto parts shop they said that belt was listed as ‘Lada Samara’! (A Lada is a Russian car make; we got them in NZ because of some weird trade deal where we swapped dairy products for cars in the 1980s...).

Some people who race prefer to run without the cam belt cover on the basis that the belt will run cooler and is readily examinable for wear. The top two covers are removed, however, the bottom one remains in place to leave the timing marks visible. It is advisable to cut away the lower portion of the bottom cover to allow gunk (technical term) to pass through and so not build up. By all accounts an additional bonus is the more audible belt whine that sounds similar to a blower drive, which may be useful in psyching out other racers...

Radiator and Thermostat 

The 4AGE comes stock in RWD form with a 5.6 litre cooling system. The use of an oil cooler in later engines with oil cooled pistons may enable a smaller radiator to be used due to the amount of cooling done by the oil. Note that all 4AGEs use the thermostat to let cold water into the engine (as opposed to letting the hot water out), hence the thermostat side of the plumbing should be connected to the bottom radiator tank.

In this manner when the water in the head heats up the thermostat will open and let cool water (from the radiator bottom tank) into the engine. Hot water leaves the engine and returns to the top radiator tank. All engines have a thermostat bypass so that water will still circulate (due to the water pump) around the engine when the thermostat is shut, thus eliminating any hot spots caused by the water not moving and also preventing the water pump cavitating.

Water Pump 

The 16 Valve 4AGE RWD thermostat and water pump plumbing assembly is the simplest to use in RWD configuration and has both supply and return on the intake side of the engine. If your radiator inlet (the top header tank connection) is on the LHS of the radiator then a FWD 4AGE top radiator hose can be used as it fits across the front of the engine and with a little modification should connect to the radiator inlet.

Any FWD engine (except 20 Valve or supercharged motors) will fit this plumbing which is the easiest way of adapting a later engine to RWD configuration. You must use a RWD water pump if you wish to use an engine driven radiator fan otherwise the water pump bearings will fail.

The RWD water pump and thermostat plumbing will not fit on supercharged motors as the supercharger is in the way. The best approach here is to utilise the standard remote thermostat assembly (normally mounted on top of the transaxle) and mount it either on the side of the engine or on the inner guard of the car with custom pipe work/flexible hoses to suit. If you know of a good, compact inline thermostat housing I would appreciate being told.

Sensor Block 

All 16 Valve engines have a sensor block at the back of the head which contains 2 water temperature sensors and the take off for the heater. On FWD cars and MR2s this unit protrudes out the back of the engine adding several inches to the overall length of the engine once hoses are attached, while on RWD engines the unit runs across the back of the head and is much more compact, adding only about 1 inch to the overall length of the head. The RWD heater hoses also lie flat against the back of the head as opposed to exiting directly backwards as on the transverse engines. These units are interchangeable between all 16 Valve engines, including supercharged models.

20 Valve 

The 20 Valve motor has a completely different head with a large sensor and thermostat block at the rear. This block also has the supply and return to the heater, and once heater hoses are connected protrudes several inches behind the head. Coupled with the distributor, which is driven off the back of the exhaust cam, installation in a normal RWD car may best be achieved by either locating the engine further forward in the engine bay (if possible) or recessing the firewall as required. Bear in mind that moving the engine further forward may result in sump clearance problems.

Both radiator inlet and outlet face the LHS of the 20 Valve engine, ie exhaust side. The outlet to the radiator is immediately behind #4 exhaust port. The easiest way to mate the radiator plumbing up in RWD configuration on the 20 Valve is to fabricate a pipe that runs from the water outlet forwards, over the top of the exhaust manifold. The pipe needs to be roughly hockey stick shaped in plan view, and can be secured to the head outlet flange at the rear LHS of the head and to the lifting eye bolts at the front LHS of the head. Inlet plumbing needs to run from the radiator bottom tank along the bottom of the engine and then up to the inlet on the thermostat housing at the back of the head.

If you are fabricating your own cooling lines be careful to ensure there are no air locks in the system otherwise you will cook your motor.

If anyone has managed to convert a 20 valve to the RWD water plumbing set up using a standard RWD water pump and thermostat I would be most interested to know. I am aware of a major effort in Australia to do so that should have worked yet water circulation was insufficient to prevent hot spots in the head. If anyone has a 20 valve head gasket they can compare to a 16 valve I will also be most interested to know if there is any difference in the water jacket passages.

16 Valve Inlet Manifolds 

With the exception of the RWD AE86 and AA63 4AGEs all other engines are configured with the throttle body facing the ‘rear’ of the car ie flywheel end of the engine. The RWD set up is the ideal one to use as the open end is towards the front of the car. On 83.5 - 87.5 engines (Blue and Black Tops) this is not a problem as the RWD manifold will directly bolt in place of the transverse one.

Later 16 Valve models (87.5 - 89.5 Red and Black Top or post 89.6 Red Top engines) all face backwards, however, it is my understanding that intake manifolds are interchangeable between all TVIS engines (ie up to 89.6 when the Red Top was introduced).

If you do not have access to a RWD manifold or you have a post 89.6 Red Top then there are two possible options (short of fabricating your own manifold or converting to carburettors); cut both ends off the manifold and swap the throttle body to the front of the manifold and blank the rear or else cut the intake runners and weld the entire top half of a RWD intake on (assuming the intake runners line up).

If bonnet clearance is a problem the 16 Valve manifolds can be shortened by cutting a section out of the vertical part of the intake runners and welding back together . My original engine was shortened 30 mm in this manner with no apparent loss in power. Be warned that this will place the cam cover breather almost horizontal and hence an oil catch tank is a wise idea. This all means that realistically the oil filler cap and plug leads are the limiting factors for bonnet clearance on 16 Valve motors.

20 Valve Inlet Manifolds 

The 20 Valve air box also has the inlet to the rear of the engine, however, both it and the trumpets it contains can be bolted on upside down, which will place the inlet at the front. Unfortunately this looks somewhat unattractive and requires even more height. The air box can also be shortened, however, it is made of several layers of thin plate and is difficult to weld. Stainless steel welding rod works best. The plastic trumpets inside can be cut and glued shorter also, however, some compromise of the smooth internal walls is required. In reality fabricating an entire air box would not be a complex operation and some side-draught carburettor trumpets are a close match.

Air Filters 

If the engine runs a MAP (Manifold Air Pressure) sensor air measurement system then you can literally fit an air filter directly on the end of the throttle body. Some K&N filters fit perfectly, however, a cold air induction system is more effective but more complex to fabricate. If the engine is AFM (Air Flow Meter) then you will need to connect this to the throttle body via a suitable tube. 20 Valve engines run an air box which a length of UK MK 2 Ford Escort heater ducting concertina tube fits nicely between the air box and AFM. A side-draught carburettor (ie Weber DCOE) type air filter with a modified base plate can be adapted to fit the AFM. Alternatively MR2s have a neat adapter that bolts on to the inlet side of the AFM that a round air filter will fit on to.

Throttle Linkages 

If a standard throttle cable cannot be made to work, or if you do not have one, then brake cables and fittings off bicycles provide an excellent cost effective source of components. Mountain bike cables tend to be heavy duty and Teflon lined. Go to a good bike shop and order stainless steel brake cables as galvanised cables will just rust up and break off . If you have the room run a dual system (two cables instead of one). Much easier to get home with a broken cable that way…

Really smart throttle systems use the springs under compression to push the throttle closed as opposed to the normal tension system. If you think about it, the compression system is less likely to fail and if it does will still provide some closing assistance in most cases.

If bonnet height on a 20 Valve is critical then it becomes necessary to remove the complex linkage system from the top of the throttle bodies and fabricate a twin side-draught type linkage that enters from underneath the throttle bodies. You may also need to shorten the oil filler cap - I certainly did… 

EFI Fuel System 

Although Toyota have their own EFI system (Toyota Computer Control System - TCCS) it is basically a derivative of the Bosch Motronic Digital EFI system. This is good news as Bosch is used world-wide by a large number of manufacturers, which means that many components are interchangeable. In this manner a fuel pump from any Bosch type fuel injected car will be adequate (assuming the flow rate is high enough) and bigger injectors can be sourced from other vehicles if you are running injection that has to feed a heavily modified engine.

If you run the EFI system then you will need a high pressure EFI system fuel pump delivering about 40 PSI. The minimum plumbing required is a supply line and a return to the tank. Either an internal (in fuel tank) pump as originally fitted or an external pump can be used. If you don’t want to buy new or aftermarket then external fuel pumps from Nissan 3 litre straight 6 cylinder engines have proven effective.

The fuel supply must be at a constant pressure so it is wise to use an internal baffle in the tank around the pump pick-up. Surge tanks may be required for external pumps, however I believe that a properly designed in-tank pick up system will alleviate the need for one. It is most important to use the correct diameter fuel lines - the supply needs to be at least 8mm and the return 6mm diameter otherwise fuel starvation will occur. Garry 'Turbo' Meisener has this to say:

"Look at the Bosch GFP-286 (this is what I run) or GFP-216 (even more flow for power crazies). These are both big time overkill for 250 hp, but they will run over 100 psi all day, and the flow is in excess of 450 hp. With a good fuel pressure regulator (I still use the original Toyota one, squeezed for 10 psi more pressure) they will never let you down. I am sure they have a smaller one, but these are the ones my friends use for big time turbo motors. I run well over 60 psi of fuel rail pressure under max boost.

Any Bosch K-Jetronic pump should do the job, they are much higher pressure then electronic systems. Look for an old Mercedes V-8 replacement pump. The GFP-216 was for the SL, SEL, etc. 560 V-8."

EFI System Wiring 

If you decide to run the factory EFI system then it is best to get the relevant Factory Wiring Diagram and as much of the original wiring loom and sensors as possible. The standard set up has 3 plugs in the ECU: two go directly to the engine with the other going to the car for such things as power feeds, instruments, warning lights and sensors etc that are not on the engine.

As the car side of the wiring diagrams are very much the same, if you cannot get the exact wiring diagram for the engine then you should be able to figure it out from the standard car. The code for the plug pins is written on the circuit board near the sockets inside the ECU, except for Japanese model 4AGZE ECUs which do not have any labeling.

If you want to run a ‘check engine’ warning light (which is also the means of displaying diagnostic codes) then you must run a speed sensor which is normally part of the speedometer. If you do not run this sensor you will get an intermittent trouble warning on the check engine light, however, engine performance is not affected. Unfortunately if you fit the speed sensor it will also limit the car to approximately 180 km/h top speed. If you do not have the original speedometer a magnet bonded to the drive shaft and a reed switch connecting the ECU to earth works. Note that the US ECUs don't have speed limiters.

Depending on the regulations concerning emissions etc it is possible to run the engines without the exhaust sensor and suffer no effect on the engine’s performance. The lack of an exhaust oxygen sensor will register as a trouble code but it will not trigger the check engine warning light. 1989-on ECUs for the US Corolla have two oxygen sensors - one directly before the cat and one after, although this may only be in California. This sensor checks to ensure the Cat is working correctly. OBD strikes again...

It is wise to utilise the ‘circuit open’ relay system which shuts down the fuel pump if the ignition circuit is on but the engine is not running (as may happen after an accident). If this part of the wiring is missing in a MAP sensor car then a relay operated cut out connected to the oil pressure switch as a trigger is just as effective, however, a bypass for starting should be fitted. This is triggered from the ‘start’ position on the ignition switch. An engine fitted with an AFM has a fuel pump switch built into the AFM unit itself which shuts down the pump when there is no air flow.

Follow this link to a comprehensive article onHow to Wire Your Car

Aftermarket ECUs 

I am not a fan of aftermarket ECUs. The principle reason is that it goes against my low buck approach, as it is cheaper to buy a complete damaged car and therefore get the entire EFI system than it is to buy an engine on its own and a separate aftermarket ECU.

Furthermore, I have yet to experience an aftermarket ECU that works as well as a factory one. I have experienced a few and none have had the crispness or response of a factory set up. The majority I have seen are almost as temperamental as carburettors - you need to adjust them to match the day, which I just cannot be bothered with.

Yes, I realise that for heavily modified engines you have no choice, but I also return to my 'bang for buck' argument about using a standard(ish) engine with the performance you want in stock form.

Toyota ECUs also cannot really be chipped. To my mind the answer is simple - run the stock ECU if you have one, and only use aftermarket as the last resort.

Exhaust System 

All 4AGEs (including the 20 Valve) have identical exhaust port dimensions and spacings. The 20 Valve has 4 into 2 factory tubular extractors while the remainder have 4 into 2 cast manifolds. The 20 Valve head manifold bolts at the extreme ends are in a slightly different location to the 16 Valve engines, however, the 16 Valve manifolds can be modified to fit quite easily, and vice-versa.

The standard RWD manifold is a wise option if it will fit in the car as by all accounts there is little to be gained by replacing it with a set of aftermarket tubular exhaust headers, however, there is much to be gained by going to a larger diameter exhaust system from this point back.

The standard RWD system has 28" long secondaries between the manifold outlet and the tail pipe junction. The TRD RWD exhaust system utilises the original cast manifold and then breaks into two 42 mm diameter secondaries that are 485mm long to the junction, followed by a 330 mm long 50mm diameter pipe to the muffler, a 640 mm long section containing the muffler and finally a 520 mm long megaphone expanding out to 57 mm diameter.

Local tubular headers I have seen are 4 into 1 design and have either 1½ " or 1 5/8" diameter primaries and a 2" tailpipe. The headers are not very precise - the RWD primary lengths range from 21-28", and FWD from 12-14". I have been told that 2.5" exhaust systems on 4AGEs are very loud and that 2.25" is a better diameter to go with.

Best I can figure (from a graph I got sent) the ideal is about 28" primaries on 4 into 1 headers for a 4AGE. The set I was building for the stillborn 4AGZE powered Ford 105E Anglia (1964 car) were 4 into 2 into 1 with 14 inch long 1 3/8" primaries, 28 " long 1 7/8" secondaries, and 2 1/4" tailpipe. This was based on the best I could figure it out and what I could get to fit. I was building them from pre-formed mandrel bends, which were to be welded together, hence I would have had a very accurate means of establishing the lengths. The primaries and secondaries would have been within a couple of mm in length to each other.

Personally I would not have bothered with a custom set of headers, especially in what was basically a road car, however, the Anglia engine bay was just too tight for anything off the shelf to fit. Also if you do not have the factory manifolds an off the shelf set of headers, while they may not be ideal, will still work and provide a cost effective solution.

Next: Transmission 


Copyright © 2000 SpeedTECH Last modified: January 23, 2000