Sam-Q'S 20V Rwd Cooling System Guide

[Sam_Q]

This complete cooling guide has been massively updated however it is now hosted on my website:

 

 

 

Complete 20V RWD Cooling Guide:

A massive guide covering multiple options in the cooling system conversion on a 4age 20V engine. Has extensive details on the merits and downsides of multiple options of every component design in a revised cooling system.

Edited October 9, 2010 by Sam_Q

[Sam_Q]

After this is all done the rear half of the housing can be bolted to the 20V front using the steel gasket of the 20V and then bolted to the engine. Seeing the front housing is slightly different it will be slightly off matching the cover of the 20V. While it will still fit it is slightly different but it is very minimal. Here is how mine looked all bolted up:

 

 

 

 

Off the rear of the standard water pump is another pipe that is needed. It normally is bolted to the back and goes under the manifold and to a rubber hose at the end. This isn't a straight swap as it fouls the knock sensor and quite possibly the manifold brace also. The easiest way around this is to just chop it off approximetly 40mm away from the flange. With this cut the rubber hose can still be used for rest of the chopped section, more on this later. I however chose to chop and re weld the pipe on a different angle, I also had to make a new bracket at the end to support the pipe and it worked out well (got lucky!). I ground and painted mine to make it look as close to factory as possible. I was quite happy with how it turned out:

 

 

 

After all this is fitted it brings up the last problem of the new water pump placement; with the new position the top the bottom radiator inlet directly fouls against the alternator as shown in this picture:

 

 

 

 

By far the easiest way to get around this is to just combine two tensioners and then angle the alternator far enough away that a radiator hose with a sharp 90 degree bend in there can fit onto the outlet. I chose the most difficult option (when don't I?) and made a new custom bracket that holds the alternator low on the other side of the engine. I wouldn't recommend this option at all because it is very difficult to make, difficult to get right, can have some very bad effects if slightly out, etc... It does however place the alternator close to the battery, in a very convenient place. Also of note since I am running no air-con and my custom mount has a traditional tensioner I managed to discard all the original engine tensioners which are heavy, difficult to work with and always seem to seize up. I used a modified Corona tensioner which pivoted off a bracket that bolted to my first extractor bolt. I think for the average person who wants to move the alternator to the other side then what I did is still a bad idea. I would instead say a mount of another 4A based engine such as a 4AFE, etc.. a 4Ac bracket might even fit.

 

 

 

 

That's it for the water pump, it can now be bolted up and left alone. To fit the pump to the block the original metal gasket from the 20V block can be used..

 

 

 

 

 

 

Custom Top Water Pipe:

 

 

With the new water pump setup in place it leaves the top water inlet of the head exposed. While this previously received water directly from the water pump it needs to be changed to be an water inlet from the radiator. Some people have cut the original fitting and re welded the aluminum to face forwards. While this is a potentially good approach it must be kept in mind that any pipe made that goes first down then up encourages an air-lock in the cooling system is therefore is unrecommended. The easiest option I have seen is to cut it off almost at the flange, weld the very end of the pipe (with the barbed end) onto the flange and then fit a radiator pipe with a sharp 90 degree bend onto it, much like what can be done with the bottom pipe. Another easy way is to cut a flange and just weld a piece of pipe in on an angle, this is very effective and simple enough. I chose the hard option once again and made something that uses all of the opening and is of a smooth and contoured design to maximise flow. I firstly copied the original and made a flange with the oval opening in the middle. From here I welded together a stainless bend to the flange with an additional section to divert the flow through the entire opening, then I welded on a straight stainless section with grooves cut into it for sealing. Initially I though this was all it had to look like and so it looked like this:

 

 

 

 

It was at this point however when I found that I had to add the provision for the bypass pipe, So my top pipe ended up looking like this:

 

 

 

 

This bypass pipe needs to face the outlet that is glued into the water pump. There needs to be room to fit the rubber pipe and the two hose clamps that are needed. I also decided to add a dip-stick mount and also the engine temp sensors to it (more on these later). Here is mine fitted to the engine without the rubber pipe in place, also in the second picture drawn in place is where the rubber hose is needed to be fitted. I left enough room so that I could bolt everything in place and then fit the rubber hose by bending it and putting it in place later.

 

 

 

 

The finished setup should end up looking something like this:

 

 

 

 

 

Dip-Stick:

 

 

As shown by the top picture I made a bracket off the water pump to hold the original 20V dip-stick in place. I have however been told that a 4Ac dipstick can be directly fitted instead. I decided to make the mount to use the original 20V item as it is a much nicer model and also it gives me piece of mind that it's right, even if it is highly unlikely that the 4Ac model has a different length. If a custom mount is made be sure to check that the dip-stick can be taken in and out easily. I initially had some problems with a position I was testing in that the dip-stick would snag against something on insertion because the dip-stick tube was on an angle. Also check that it isn't held too close to the water pump pulley, I moved mine further way that was was necessary because I plan to fit a larger water pump pulley later for an under-drive.

 

 

 

 

 

 

Rear Bypass Plate:

 

 

While one other 20V RWD guide suggests drilling a hole in the back of the head I think this is a bit much and risky, it also might cause a limitation in flow and also makes it impossible to use the engine in Front Wheel Drive form ever again. Instead a better way in my personal opinion is to have an external bypass. Firstly unbolt everything off the back of the 20V head and throw it in the bin, it isn't needed. After the head is stripped looking at the back reveals two holes for cooling and three threaded blank holes for mounting.A thick plate needs to be made that can comftabely cover these outlets and be held in place by the three threaded holes. A thickness of about 20mm is ideal and aluminum is highly recommended. I had a threaded hole in the middle of my plate for a temprature sensor, this is the hole in the middle, ignore this as it isn't part of the mounting, heres how it looked:

 

 

 

more below ....

[Sam_Q]

Now a slot needs to be cut into this plate, The slot needs to be there to flow from one outlet to the other. While I used a milling machine which is the recommended way it would be in possible to do it other ways. It would be possible to do it with a die grinder and an aluminum cut carbide burr. Also potentially possible but unrecommended is with the careful use of a grinder and a grinding wheel intended for aluminum, don't use a normal grinding wheel!! The picture below is mine seemingly finished, I later changed my mind on having a temp sensor mounted in the middle and instead chose to plug the hole up.

 

 

 

 

Lastly when this is made it's a very good idea to leave the two threaded holes above this alone and very free, these I recommend to be used for an engine mount.

 

 

 

 

 

 

Side outlet:

 

On the exhaust side of the engine to the right of the exhaust flange is an outlet that normally has a radiator hose fitting on it. Take this off but keep the gasket. Make a plate up that covers this hose and if no heater is going to be used then bolt it back up with the gasket to just block it off. However if you are like myself and want to keep the use of the heater then this needs to have a small outlet placed into the middle of it to go to the heater core water flow control valve (next to clutch master cylinder). It needs to look like so:

 

 

 

 

Heater hoses:

 

To get the heater working again various heater hoses need to be fitted. For this hose joiners need to be used, I bought a brass item from Super Cheap Auto but I have seen an ever cheaper plastic product with two included hose clamps from a Service station sold as an emergency repair kit but I wouldn't trust it long term.

 

Here is the final layout as it is installed, keeping in mind that this engine had no transmission on it at the time and so it was tilted forward. Normally it would lean significantly further back and have the distributor base almost touching the heater core hose.

 

 

 

 

Firstly both of the original heater core hoses are kept, although one may need to be lengthened. Also before the engine is installed one pipe should be cable tied to the metal lines behind it when it goes near to the distributor base, it should be made to fit as close as possible to the firewall for clearance reasons (See above picture: pipe #3). The rest of the pipe is fine in the factory position and will not interfere.

 

The other heater core pipe it is the hose that goes from the heater core on the firewall then across and down to next the block on the drivers side (See above picture: pipe #2) . If the pipe is kept close to the original layout as it was on the single cam then it will fit straight on. Otherwise if only a small section of metal pipe was kept on the rear of the thermostat housing then a simple joiner and a straight section of heater hose will be just as good. I wouldn't at all recommend running a new straight water hose all the way to the heater core as the original can hug the body very close which is exactly what is wanted with a 20V install.

 

The last pipe is a totally unique item and no off the shelf part can fit, it goes from the outlet on the side of the head to the heater core flow control valve. (See second picture below. For this I used a heater hose intended for a Gemini, I chopped it in the middle, added the joiner, rotated it on the join 180 degrees, clamped it back up and then cut a short section off one end. The picture below shows what it needs to look like and where the hose joiner can be added.

 

 

 

 

It will need to be fitted as shown bellow

 

 

 

 

With these pipes in place the heater should just as well as it did before the conversion.

 

 

 

That's it!

 

I am still working on this guide and will continue to edit it, so if there are any suggestions or corrections then I want to hear it. I want people to know how to do this to curb the horrific 20V installs and misconceptions that are so common. If you have a picture that you think might be of help if it is added then please contact me.

 

 

For all questions please let me know at:

 

daunderdweller @ hotmail.com (remove spaces)

 

which is also my MSN instant messaging account

 

 

or just send me a friendly PM

[Jono]

thanks heaps for taking the time to write this guide, good guides like these really help people with their conversions.

[Des]

If i could + rep i would, 10/10 buddy.

[Sam_Q]

no problem at all guys

[Jono]

what did you do with the plenum?

[Sam_Q]

here my worklog:

 

http://www.rollaclub.com/board/index.php?showtopic=9903

 

but heres a direct answer:

 

 

[Neilm]

Hi Sam-Q

 

Just found this thread as I am looking to RWD a 20valver

 

Is there any reason why you didnt just use all the RWD AE86 water pump and thermostat housing assembly ?

 

Cheers Neil

[Sam_Q]

yes good question, although described in more detail in my extended version of this cooling guide I used this method because it uses the available parts, as the 20v parts would be there from the upgraded engine and the 4ac parts because thats what the 20V would usually be replacing. The RWD ae86 parts were only ever available in the Trueno and hence are far from common, however they can be purched brand new from what I hear.