Can those who have carried out an engine conversion on their polo please write a few words regarding the swap and include a few pictures if possible. Please rate the feasibility of the swap, i.e was any welding required, what was plug and play and what wasn't etc. Only reply with conversion info, do not post questions. Please PM the authour of the reply for further info.

MK4 polo gti

I converted my polo 16v to a mk5 gti powerplant when my cam belt tensioner broke and trashed my original engine. The swap is pretty straighforward in all post 98 polos (not impossible on earlier mk4's but require a little more wiring).

Parts required from GTi

Engine

Gearbox

Drivers side engine mount

ECU

Pedal box

Fuel pump

Engine loom

Interior loom

98 onwards headlamp switch

GTi clocks

Mk5 window motors and switches

Mk5 tail lights

98 onwards indicator stalks

I'd also recommend the front brake setup from atleast a 16v

Fitting

The engine lines up onto the original mk4 mounting points (chassis leg and gearbox). There is no welding required at all.

I removed the wiring from the mk4 and replaced it with the entire mk5 loom. You could use the complete dash from the mk5 if you chose to once you have fitted the new looms. This would save on having to splice parts of mk4 and 5 loom together for things such as headlamp switches and heater controls. Essentially you are building a mk5 in a mk4 body shell.

Evaluation

From my point of view this is one of the easiest engine conversions to carry out. Its fairly self explanitory all the way through if you are reasonably able when it comes to car mechanics.

This is only a basic guide, I take no responsibility for problems anyone may encounter trying this swap. I have a zip file of pictures available for anybody wanting to try the conversion. Most of the long standing members will remember the trials and tribulations I encountered. If I was doing it again I would probably not bother. The power gains (25bhp) were not that noticable, a 16v with a few choice breathing mods would be more than capable of similar performance.

Converting a Polo GT to a Polo G40

A pretty common swap, mainly because it offers lots of power and is so damned easy! My conversion was complete within 48 hours thanks to Andy Strange. However, this is something that anyone with a decent set of tools, a garage, an engine hoist and a garage can do, albeit over more time I'd imagine.

What you need from the donor car

- G40 engine

- G40 gearbox - The CL's 8P box can also be used, G40's ATV is better.

- G40 supercharger

- Intercooler

- Wiring loom and ECU

- G40 brake calipers, carriers and discs (if you haven't already!)

- Driveshafts (optional, original ones still work)

- G40 160mph clocks (also optional)

The procedure (in a nutshell)

Begin by ensuring the car is left overnight to get cold, or you'll burn yourself! Switch the heater controls to hot so that the coolant can drain properly and remove the bonnet.

Next strip the GT of its induction system (airbox and associated pipes) and drain the coolant by then, starting at the front driver's side and working back to the ECU, begin unplugging the wiring loom. Then unplug the wiring loom from the ECU and withdraw the whole lot including the fuse box.

Unplug the ignition leads and remove the dizzy cap. Remove the throttle body, fuel rail and inlet manifold. Disconnect the pipes to the heater matrix. Disconnect the wires to the starter motor.

Your engine bay will now look something like this:

Next put the car on axel stands and unbolt the downpipe, pull this free from the rest of the exhaust system. Unhook the gear selector from the back of the gearbox. Now attach the engine hoist to the hooks at the back of the head and jack the hoist up a little so that the ropes are tight.

Unbolt the engine from the chassis at its three engine mounts, remove the nuts that hold the driveshafts onto the gearbox. You are now ready to carefully remove the engine and gearbox from your engine bay. Watch to make sure nothing is still attached to the car as you lift.

And out it comes!

While the engine is out you may want to clean the bay up a bit, this is up to you.

Fitting the G40 engine is a reversal of what you have just been doing. Gently lower the engine and 'box into position, aligning the driveshafts as you do so, then bolt the engine to the car using the three engine mounts. Once the engine is in place, check that the driveshafts spin freely and that all the nuts are tight, then re-attach the gear selector rod and check that the gear change is ok.

Now re-attach the coolant hoses and bolt the G40 downpipe onto the exhaust manifold. Connect the starter motor to the cable, but don't plug it into the battery yet.

If you are fitting a non-standard G40 charger or a smaller pulley, you may now want to transfer the G40 fuel rail and throttle body to the GT inlet manifold. The G40 one is more restrictive, but better suited to stock engines than the GT one I believe.

Bolt the inlet manifold and throttle body with boost return back in place then carefully route the wiring loom back through the engine bay. Connect up the ignition leads.

Remove the front bumper and bolt the intercooler bracket in place, then attach the intercooler to the front crossmember. Remove the fan cover from your old engine, and replace with the G40 one. Now fit the boost pipes from the intercooler to the throttle body ensuring that all are tightened securely.

It will now look something like this:

Next, bolt your G charger in place, attach the oil feed and ensure that the V belts are tight. If you are keeping your boost return pipes, attach these now. If not put your blanking plate onto the vacant inlet on the charger and connect some hose up to the crankcase breather pod on the back of the engine block.

Now fit your air filter/induction kit to the other inlet. Refill the coolant system. Connect the battery.

Check to make sure that you haven't left anything unplugged then cross your fingers and turn the key.

It is worth getting the G40 brakes on before you take it for a spin, these are a straight swap for the existing GT brakes and a simple job to change. Don't forget to bleed the brakes after you swap them though!

Job done!

Worth replacing while you're doing this...

- Both fuel pumps - not cheap, but cheaper than an engine rebuild

- Gaskets - inlet manifold, throttle body, downpipe, exhaust manifold

- Cam belt and water pump

- Get the charger serviced

- Service stuff; air filter element, plugs, leads, dizzy cap, oil and filter etc

- Clutch

- Gearbox oil (if you can take the smell!)

- Engine mounts if the rubber seems tired

Extra stuff for non-GT owners:

- You will need to change at least your inline fuel pump if you have single point injection, your stock one won't be up to the job

- The expansion tank on a GT/G40 has a connection for plug that says when you're running out of coolant, don't forget to get that too. If the conversion doesn't come with it, GSF sell them for £15. (thanks to Jon_S for that)

- It will also be worth you looking at getting a GT/G40 rear beam, as this has a second anti-roll bar

Evaluation

Lots of fun to be had with this engine conversion; damned quick as standard, dead simple to get more power and it sounds awesome too.

But MAKE SURE YOU CAN LIVE WITH THE COSTS!

G40s aren't that light on fuel and require constant attention. PTFE lube in the charger every 1000 miles if you've removed the boost return, new charger timing belt every 10,000 and a full charger rebuild every 30,000 miles is advised. It's worth it though.

To those more in the know than me:

PM me to if you spot anything that I've left out, but I can't remember there being anything else!

The rough guide to the 1.6 GT conversion.

Sourcing an engine. (AEE/ABU)

First things first, don’t pay much more then £100 for the engine. If they try and persuade you with the ‘It comes with everything’ tell them you don’t need anything other then the engine itself. Don’t be tempted to buy the whole lot and sell the rest separately as there isn’t much demand for the parts. The only things worth getting are the exhaust manifold and downpipe and oil breather that is bolted to the back of the engine and that’s about it. Everything else will be from a mk3 polo.

So once you have yourself an engine remove the existing parts, engine mounts, inlet ect depending what it comes with.

Engine mount

You can put the mk3 front engine mount on straight away (I used new bolts to be safe) this raises the first issue, no third bolt. You have a few options, cut and weld a piece in, make a bracket that goes to a lower casting hole or leave it. I made a bracket out of 7mm steel, literally goes from the third bolt to a lower cast hole, if I remember rightly it sits flat so a straight piece of steel should do the job. I have also heard of people using higher tension bolts which seems like a good idea if your going to just have the two. Some minor trimming needs to be done on the cam belt cover so that the mount doesn’t push it inwards.

Cam belt change

The next job is to change the cam belt, tensioner & water pump, before you put the engine in otherwise you will regret it later on. So remove the alternator pulley which usually will be a lot wider then the mk3 item this needs to be changed otherwise it wont clear the mk3 chassis leg.

Mk3 Alternator pulley

Once you have had fun changing the cam belt, tensioner & water pump offer the mk3 alternator pulley to the position, you will now find the tensioner bolt rubs on the mk3 pulley, if so you need to grind the head of the tensioner bolt slightly, literally 2-3mm will do so be careful not to go to mad. Once happy fit the pulley (use new bolts if there rusty).

Lower cam cover

Now fit the bottom cam cover, the shape of it means the mk3 pulley rubs on a certain area (the part that bevels in for the tensioner bolt ironically) You just need to trim it so it fits, 5 minute job just make sure nothing catches on the cam belt before putting it all back together.

Flywheel & Clutch

If your going to use the mk3 polo gearbox you want to scrap that huge flywheel! Remove it and replace it with one from a mk3 (there might be an adapter plate in place just remove it and the mk3 flywheel will fit no problem. You also need to use the mk3 clutch and bell housing. (make sure you use new bolts for the flywheel and torque them up properly!) Its well worth using a new clutch, I used a clutch with unknown miles and its just started slipping when booting it! So don’t be tight as the torque of the 1.6 will kill a half knackered clutch.

Gearbox

I used the 8P box from a 1.3 CL mk3 polo, I was tempted to use a GT box but decided against it as I knew the 1.6 would have enough grunt to pull well on the longer box. Make sure you use a healthy box with new oil otherwise you might lose some gears!

Inlet manifold

This is the big one, it doesn’t fit simple as. The bolt holes are so close its annoying. Two sensible options, have the head welded and drilled (exspensive) or have two inlet cut and shut. Niether are particularly good fun. I was quoted £400+ to have the head done which was a big no no seeing as the idea of this project for me was to get standard G40 power for GT conversion money! So the next problem is, all the AEE inlets are plastic, can’t weld with that. However the ABU inlet is aluminum. I found a mk3 Golf and took its inlet. I then spoke to a lot of people about how to cut and shut the inlet. The welding wasn’t much of a problem it was the cutting, it needs to be flat so using a saw and a vice isn’t really ideal.

I managed to persuade a local engineering company to have a go at it and they quoted me a very good price seeing as they didn’t know how long it was going to take. The main problem here is that most places, when you explain what you want doing run a mile! So ABU inlet, cut the flanges off, do the same with the GT inlet and weld the ABU flanges to the GT inlet, easy…

Mine turned out very well, there’s some material that can be ported later on but I haven’t got round to that yet.

You will also need to make some sort of bracket for the inlet to give it some more support, using rubber mountings is a good idea to avoid cracking the welds.

Alternator

When fitting the mk3 alternator and bracket you will find it touches the oil pump cover. Just lightly shave some metal off so it can fit as per the picture.

Starter motor

If using the mk3 flywheel you need to use a starter motor from a 1994 mk3 polo. The AEE one want even turn the engine due to the distance difference in the flywheels.

Coolant system

The GT thermostat housing won’t fit without re-drilling the head. Use the housing & the water pump pipe from the AEE. This also means you need to mount the ISV somewhere else as its bolted to the GT water pump pipe. You can just cable tie it in place where it would normally sit. You will also need the radiator hoses from the AEE as the mk3 ones are too short.

I would recommend using a new thermostat housing and thermostat as they can crack and leak as they get old.

Downpipe

If you use the mk3 exhaust manifold and downpipe you will have problems straight away, because the block is taller it doesn’t clean the ARB and various other things. You can either extend the downpipe or do what I did and use the AEE one.

I used the downpipe from the AEE that had, had the CAT cut off so some extra pipe needs to be welded on.

Oil sensors

The AEE head only has one oil sensor where as the GT runs two, the best way round this is to use a oil feed adapter from a G40.

Injectors

The Polo GT injectors wouldn’t cope too well with this setup so you need to use different ones. I’m currently using Golf Gti injectors which are slightly overkill but seem to work ok, however there are many available from different makes and models. You basically want somewhere between GT and G40 cc.

Cam

You will want to use the GT cam for a bit more power, the timing marks don’t line up so you need to be careful and make sure its setup right. I cant go into detail as I haven’t done it yet.

Parts & tuning

GT parts

Inlet manifold

ECU

Engine wiring loom

Throttle body & piping

Airbox & pipework

Camshaft

Clutch & bell housing

Flywheel

Engine mounts

Gearbox

HT leads / Dizzy + cap

G40 Parts

Backbox

Straight through centre section is worthwhile

AEE/ABU parts

Exhaust manifold & downpipe

Engine

Golf Gti

Injectors (8v)

Air flow meter

Conclusion

I don’t think I have missed anything significant out, there’s possibly a few more things but nothing I can recall of so they can’t be that serious. It’s a worth while conversion as long as your prepared to do some head scratching. In terms of performance it will eat almost all GT’s that are still running GT management, even cam’d and chipped examples. Great fun to drive loads of torque and they do rev nicely with the light flywheel.

You can see my build thread here

Enjoy.

Ash Carver

Shocked that no one has put this in here, the information here i got from GAZ, legend.

MK3 Polo AAU to ABD ( 1.4 8v)

You need:

ABD engine ( from K reg, L reg and some early M reg mk3 Golfs ) the engine will look identical to the AAU engine, also same rocker cover.

AAU thermostat housing so both sensors fit your AAU loom, so will also use all AAU water hoses

Either AAU or ABD clutch

Either AAU or ABD fly wheel

Either exhaust manifold

AAU alternator and tensioner bracket

AAU alternator pully wheel off the side of the AAU engine will be needed, to use the AAU alternator, so swap them over.

AAU engine and gear box mounts, iff you have put a 5 speed gear box on the AAU already then use them gear box mounts

AAU and ABD single point injection ( SPI ) air intake units are the same ( big dome air intake ), only differences are the breather pipes at the back connecting it to the bottom end of the engine, use ABD both hoses for this, 2 in total, one to rocker, one to air intake unit

Either ABD or AAU inlet manifold

Either ABD or AAU throttle body

One water pipe that comes from the heater matrix will be a tight fit over the metal water pipe on the back of the ABD block, but will fit when lubed up

AAU ECU is to be used as the ABD connection is different, will run fine

AAU and ABD starter motor can both be used, AAU is smaller in size

AAU ignition leads, spark plugs, dizzy and coil are all fine, ABD ones are fine too

Fitting :

In my opinion the easiest conversion there is to do, on a MK3 Polo that is. It literally is plug in and play. All that is needed off an ABD is the top end and bottom end, no ancillaries needed, all will come out of the AAU you are upgrading.

Evaluation :

BHP when the conversion is done should be approximately 59 BHP, the car is significantly quicker off the mark and top end. The car will no longer pretend to be a snail when you have passengers lol. Further upgrades like a GT cam, bigger bore exhaust, 600 cc bike carbs set up correctly will take the car to being in the region of 100 BHP with out cutting, welding or hard core modifications.

Edited 24 December, 201213 yr by dart_strife

Small question about the ABD conversion above, instead of using AAU parts could you use AAV ones instead?

Thanks.

Small question about the ABD conversion above, instead of using AAU parts could you use AAV ones instead?

Thanks.

yes, both are SPI so both can be used, i even used the ABD inlet manifold, ABD throttle body. however an AAU ECU can only be used with an AAU loom, AAV ECU with an AAV loom, ABD ECU with an ABD loom.

I have a 91 MK2f 1.05 its a HZ engine code and runs with a carb and no CAT.

Unusual I gather as MK2f are normally thought to be spi on the 1.05 but it is definitely a MK2F and definitely a carb engine.

Is this more commonly on regualar MK2s?

Anyway the head-gasket has just gone and I've been spinning my wheels trying to work out what to do.

I had lined up a 94 Polo CL 1.05 AAU but the seller tried some very shifty moves and that avenue is definitely off the cards.

But while I was going into that I sourced a nice ABD 1.4 with a 5 speed box which I was going to drop into the 94 Polo.

That having fallen through I wonder if I could fit the ABD to my much love 91 Polo and get it back on the road?

Input is REALLY appreciated as I have never done as big a job as that before and don't know much about it.

I'm in Ireland so alternative spares are just non existent and the only other Polo similar to mine on the market is totally out of my budget at £1400!

it is basicly a plug and play fit.

Keep in mind you are switching from carb to injection, so fuel tank, fuel pump, ecu, parts of the loom etc etc is al needed.

So, dont know what you are going to do with the 94 polo, but you can use that for parts to fit the abd in your 91 polo.

Keep in mind the exhaust for the polo is a bit restrictive, so upgrade to a g40/gt exhaust is a must really.

Abd flywheel is massive compared to a aau flywheel I'd reccomend fitting the smaller flywheel (aau) with new stretch bolts, g40 flywheel bolts fit. Also standard aau starter

Edited 10 March, 201511 yr by Buxton

Hello people I'm going to be doing the abd conversion as said above the abd ecu can not be used with the aau wiring could you swap the chip over? Or just run a performance chip for the aau?

Chip for the aau is best bet, keep standard aau injection on, and the lambda will correct the fueling, don't expect it to be a lot quicker, it will get up hills easier and be abit more fun but will leave you craving for more power :)

Ok cool thanks for that was just thinking that I would be best to have the abd Tb n that on for a bit more poke , yes I just want a little more power that's all I've had my fun in a g40 I had bags of power and lots of fun , I just thought it would make it a bit better with the 1.4 in and a 5 speed box as the motorway is no place for a 4 speed around town it doesn't really use fuel but I watch the fuel go down fast on the motorway !

The abd Is not easy to find they only ones I have found arnt in this country , can only find that aex !

Aex is just rubbish, thiers a company on eBay who have a picture of loads of engines on a shelf I got mine from them, failing that look for any mk3 golf 1.4 breaking, most of the time it's an abd engine. I messaged a seller about one a month ago and he was prepared to post it and everything! But I couldn't afford it at the time Good luck ps look for the earlier ones with a steel rocker cover, mines a late abd (96) but it's still fine

Edited 17 June, 201511 yr by Buxton

The AEX was used in early 6n's right? Replaced by the APQ? If my APQ was anything to go by it was pretty gutless.

Made like a Swiss cheese, if your sourcing an engine to improve your car may aswell source something better, why not go for an afh on carbs? Plenty of power and reliable.

Thanks Buxton I will check them out and message them I'm in hospital ATM but hoping to

Get one in the next month or so I did check out two as they were cheap and would of got a friend to grab it but like I said was the aex , do you think it's worth doing the abd? Just thought it was really easy to do so probably the best thing to do... I am

Pretty handy with cars I used to work in a garage but wouldn't say wiring was my strong point so that worries me doing the afh ... But I would love to have afh rather than the abd ....

All depends on what injection or carb(s) your going for an afh on carbs can get very good power, with little wiring.

People have used the aex, but not worth it in my opinion

Well if it's easy with the carbs and reliable I don't mind doing that ...

Easy could be an understatement. If you go with bike carbs, i recommend a bike fuel pump

Yeah bike pump all the way for reliability.

For months I chased a problem with my engine cutting out after a few miles. I had a facet pump with T-piece return which is a tried and tested method. Turns out the carbs were running pout of fuel. Added a bike pump and things were fine. They also automatically switch off when there is enough pressure and the carb bowls are full. No brainer to me

Well yea guess it's not actually going to be easy thing is i don't want to have the car off the road for too long and too much messing with wires .. But also would like a dicent power gain how good

Would the abd with a gt cam be ...

Yeah same problem here with a facet and t piece everytime I put my foot down for about 30 seconds it would starve itself of fuel, bike pump works perfect, I did autotests and even hammering it up the steepest of hills and it worked perfect.

Edited 18 June, 201511 yr by Buxton

Tryed that company you said on eBay Buxton they are £100 plus £50 delivered but they don't have any in ATM .as for the wiring on the 16v how long did it take you to do? Still a whole loom change ?