High Capacity Radiator & Electric Fan

With the work that I had done to the engine, including high compression gas flowed head, Piper camshaft, twin SUs carbs etc., I found that the Coupe got up to temperature very quickly and hovered at the top of the normal range in normal driving and only dropped to the centre of the normal range at speed on motorways and dual carriageways.  If I had to wait around in stationary traffic, the car started to splutter and mis-fire, finally conking out and refusing to start until it spent 10 or 20 minutes cooling down.  To avoid this and make the car more usable day to day, I ended up doing three things to control it all. As an additional bonus it will mean that the car will run a little quieter and maybe even liberate a bhp or two in the process.

Stage 1 - to improve the cooling I needed a better rad, I could have a special aluminium one made up or find a lower cost solution - some research showed that the Leyland Sherpa range uses the same size radiator with slightly different fittings, its advantage is that it has 30% more cores than the Marina one, improving the rate of heat dissipation.  I had an existing knackered Marina radiator re-cored with a new Sherpa core at my local radiator company.  You can see the difference in the picture below, the new one is on the left, the cores are closer together.  I had some plastic washers inserted so that I could fit a cooling fan later if necessary.


I had hoped that this might be all that I needed to do to cure the overheating, she certainly ran cooler when on the move, but just like the original radiator it only worked when there was air passing through it.  At this stage the car still used its engine driven fan and it doesn't pull enough air to keep the tuned engine cool.  And so onto stage 2.


Stage 2 - add an electric radiator fan - I didn't particularly want to fit the fan behind the radiator (a sucker fan), because to make them work well it is usual to have a radiator shroud so that all the air is drawn through the fan.  The alternative is to mount the fan in front of the rad (a pusher fan).  There are three issues to address, firstly if you want to leave the radiator in situ without changing the rad mounts you need to fit it into the gap between the rad and the front cross member/valance, secondly work out how to mount the thing simply and thirdly find a quiet fan.


The gap in front of the rad is 2" (51mm), so a narrow fan is the order of the day.  I found that SPAL has a range of 2" thick fans of 11" or 12" diameter and they can be had with straight or curved fan blades (curved ones are quieter).  They can be bought from SPAL dealers and also from EBay.  However if you pop down to your local car breaker, you'll find SPAL fans on many Fords.  I bought new via EBay, be careful - I was sold what was described as a 12" fan and when it arrived it was an 11" fan. 


There is no standard Marina fitting kit available and I had gone off the idea of pushing plastic ties through the rad as I had originally planned.  My local rad company told me that the plastic ties, usually wear through one or more core rod in about two years, meaning a repair.  To avoid all this I looked to replicate some of the latest way of fitting aftermarket fans.  I used some 40mm aluminium angle from Homebase, drilled to accept the rad posts top and bottom.  Then some strip steel to hang the fan from, bolted to the plastic brackets.



The picture above shows the early version, after I had profiled the the angle bracket with an electric jigsaw (I trimmed more off later).  This enabled me to use the standard 1.8 radiator mounts and once I was happy with it, I took it all apart and sprayed it all matt black.  Fitting was straight forward, with just some minor fettling to seat it all in, check particularly the position of the bonnet catch mechanism, so that it avoids the fan frame.  If I did this again I would move the fan further to the left in this view.



The next step was to work out how to switch it on and off.  The common way for an aftermarket fan is to use the Kenlowe type of temperature probe as a trigger, the advantage of these are that the on/off point is adjustable.  Most original equipment fans are switched using a temperature sender which screws into a port actually mounted in the radiator.  Clearly this wasn't an option, but Pacet can offer a range of modern plastic housings that are inserted in the rad hose, different units have different diameters for different hoses.  You then have to find a suitable switch unit, my research showed that the B series runs best at around 90 degrees.  I bought a Pacet housing and chose a dual temperature switch which comes on at 95 degrees and stays on until the water temperature drops to 86 degrees (FAE pn 37030), this is actually a Jaguar V12 rad fan switch.  I connected it through a  relay, via a fused live feed directly from the ignition switch, using some suitable heavy duty wire as the fan can draw up to 30 amps.  FAE list a range of generic fan switches with different On and Off temperatures, so you should be able to find a switch to suit your engine.  When buying the Pacet housing make sure that you use the right thread, this one is 24mm across.




I want to use relays on some other circuits so I have fitted an auxiliary fuse box on the inner wing and will fit a multi relay box below it.


Stage 3 - As an engine runs hotter, the cylinder temperatures can exceed the operating range of the spark plugs, this causes mis-firing as the insulation breaks down.  The fix is to run "colder" spark plugs, which perversely means that they run at a higher temperature without breaking down.  I prefer NGK plugs, the standard 1.8 (and 1.3) Marina plugs are BP6E (or BP6ES),  my research found a recommendation for tuned B series to run BP7ES, so that is what I have bought.


So far I seem to have overcome the overheating problem.  I have yet to remove the mechanical fan and I won't until I have fitted an override switch on the dashboard, so that's the next job.