Hi, this topic has been covered a few times but I hope what I write here might be of use to some mainly as I've tried to refine and optimize my solution to make it more acceptable for everyday use rather than as a backup. I include product numbers and costs if you'd like to try.
Firstly, many have fitted an electric fan but have needed to modify the metalwork for it to fit or fitted a small one as an auxiliary. I had a Chinese cheap model and it lasted less than 2 years previously and generally it was crude but worked but it made the kind of racket that made people look and not in an admiring way.
Well perhaps I've found the very biggest that will fit without surgery: a Spal 16 incher. It's a beast and boy is it tight. You have about 1cm of up-down wiggle room and it won't fit as pictured because the "lugs" in the centre motor hub stick out! Turn it 45 degrees so they clear the narrowing valance and you have literally 1-2mm to spare!!! You'll notice I did make a mount using M6 threaded rod and some metal "L" brackets used in construction. Cost under a fiver and I'm happier with this than using the pull ties through the matrix. As the standard Spal mounts are too big to clear the edge of the rad, they are connected to the fan with a "noodle" and and M6 bolt with plently of loctite and spring washers. If I was thinking at the time, I could have folded the bracket 90 degrees over the back of the rad and bolted it to the two captive bolts and not drilled the top of the rad itself (oh well...) I'll paint these black eventually so its less obvious. It is front mounted which actually isn't the optimal position. However I'm very happy with the extra spanner room engine side, especially as I didn't refit the now pointless shroud.
The model is a Spal VA18-AP51-C41S for reference. It wasn't that easy to get actually and twice I was supplied incorrectly with the half as powerful VA18-AP10-C41S http://www.spalautomotive.com/eng/produ ... AP51_C-41S You really want the 51 and not the 10. One guy on Amazon successfully cools his 289 Mustang with it so it should be enough.
Most fans which shift anything like enough air are absurdly loud and to the most part unnecessarily powerful in normal, general use but you do really need that overhead in reserve. To this end I firstly focus on efficiency rather than outright power and cover as much of the matrix as possible, although the fan is around 150W. From my experiments the P6 rad is pretty effective, indeed as long as you keep moving a I proved a fan is unnecessary even in 34 degree heat. It seems to have specific problems with the tight packaging of the engine bay and the total lack of airflow when parked or in traffic. My solution is that often used in the 1980s and 1990s; use a two range thermoswitch. This feeds through a resistor to lower the power of the fan in general use and still has emergency "hurricane" mode to protect the engine in extreme conditions. It's also far more elegant and/or less leak prone than hacking hoses or sticking things through radiators. This is a standard M22 x 1.5 threaded item and there are HUNDREDS to choose from. Plymouth radiators did an excellent job for £20 (as they did 25 years previously to repair an earlier P6), so doing the job properly is cheaper and gives you more choice than the various kits you can buy.
Now the next issues I had were the themoswitch itself and the resistor value to control the fan. Reading up about resistor packs on various cars, it seems values vary between 1 ohm down to 0.33 ohms. Now the values I saw are all standard values in electronics which leads me to believe this isn't super matched to the application merely a balance of what is enough to cool the engine with the minimum of noise. From the figures the fan draws about 12A @ 13V, so about 1.08 ohms of nominal resistance and 150wattish output. So I bought a couple of 100W 0.47ohm resistors as a pair meaning I can get 0.235 ohm or 0.94ohms in parallel/series as well. Adding the single resistor makes the series resistance about 1.5ohms and drops the power to 112W - however the relationship between power and airflow and indeed the mechanical properties of the fan isn't linear so its more of a drop than you might imagine. It is MUCH quieter and cools well enough and I might try some other values out.
There is of course another advantage of this. The startup currents are very high, this drops the load from 12A down to 8.34A and it's much less of a strain on the thermoswitch relay. Even when it changes up to high speed as there is already back EMF the transient draw which can be over 25A is much reduced.
As for the thermoswitch itself I got this wrong to start with. I had a VW one with the ranges 102C - 91C and 95C - 84C. These are switch on and switch off points respectively. For the lower range 95 degree cut in is fine, but 84 degrees is too cool for an 82 degree thermostat as it's barely open. What tends to happen is the fan switches in and then hardly ever switches off. In the end I swapped this for a Volvo one (reference: Intermotor 50174) with the ranges 100C-95 and 95C-90C allowing 8 degrees over the opening point of the thermostat; 95 degrees pretty much being the "fully open" point of the stat. The car sits quite happily just over the 85 degree mark all day. If I park up in the sun I can't get the upper speed to kick in even in 35 degree heat after 30mins - good enough for me and it doesn't wake the neighbours. If you wanted it to run a couple degrees cooler then a Peugeot/Citreon one might be better as 97C-92C and 93C-88C ranges still allowing 6 degrees over the thermostat opening. However the P6 with a high pressure system can relatively happily work well over 100 degrees. Indeed later engines perhaps ill-advisedly work as normal at 110 degrees. I reckon 90-95 is fairly optimal.
What I will say is this is a huge load on the electrical system, you really feel the fan "rev up" with the engine as the alternator powers up. I have no idea how the guy with the 240W Kenlowe doesn't just melt his electrics and I'm not convinced that despite this power 13" will cool as well as this 16" given this covers more than 1 and half times the matrix area. You really absolutely NEED a 25amp separate fuse. I put mine on the always powered circuit as I'm happy to let the fan "run on" when stopped. Hopefully as well as avoiding localized boiling it might had I not solved this problem with an electric pump prevent vapour lock.
As a bonus, the engine is so much quieter without that mechanical lump spinning around. A large part of what I assumed was top end/tappet noise is actually a function of the engine fan spinning around. Perhaps it'll save the water pump bearings too. If you have a manual car consider it a cut-price flywheel lightening. It certainly seems a bit more "revvy".
Overall I'm not convinced of any economy or warm-up claims but what is nice is driving the car in summer, even in the heaviest traffic with both eyes on the road and not one on the temperature gauge. What might be a benefit come winter time is a bit more output from the heater but we'll see about that.
As I said this is a cooling project and not just a fan fitment and I also fitted the MGB expansion tank. Nice to know that top 2" of the rad is being used. I ditched the front number plate plinth as the Swiss plate is much smaller than the UK one it is modeled on. More airflow for free.
Overall the fan was expensive as you really need decent sealed bearings and Spal are about the best in the business. £120ish, the thermoswitch was a tenner off ebay, the resistors were £4 for two and the work on the rad £20. So allowing for cable, crimps, fuses and various nuts, bolts and brackets call it £155. What I would do differently is find an expansion tank with a coolant level warning and wire an indicator on the dash (maybe make it light up the choke warning so it looks original - I can even just use the "Otter" switch wiring) for extra peace of mind.
Firstly, many have fitted an electric fan but have needed to modify the metalwork for it to fit or fitted a small one as an auxiliary. I had a Chinese cheap model and it lasted less than 2 years previously and generally it was crude but worked but it made the kind of racket that made people look and not in an admiring way.
Well perhaps I've found the very biggest that will fit without surgery: a Spal 16 incher. It's a beast and boy is it tight. You have about 1cm of up-down wiggle room and it won't fit as pictured because the "lugs" in the centre motor hub stick out! Turn it 45 degrees so they clear the narrowing valance and you have literally 1-2mm to spare!!! You'll notice I did make a mount using M6 threaded rod and some metal "L" brackets used in construction. Cost under a fiver and I'm happier with this than using the pull ties through the matrix. As the standard Spal mounts are too big to clear the edge of the rad, they are connected to the fan with a "noodle" and and M6 bolt with plently of loctite and spring washers. If I was thinking at the time, I could have folded the bracket 90 degrees over the back of the rad and bolted it to the two captive bolts and not drilled the top of the rad itself (oh well...) I'll paint these black eventually so its less obvious. It is front mounted which actually isn't the optimal position. However I'm very happy with the extra spanner room engine side, especially as I didn't refit the now pointless shroud.
The model is a Spal VA18-AP51-C41S for reference. It wasn't that easy to get actually and twice I was supplied incorrectly with the half as powerful VA18-AP10-C41S http://www.spalautomotive.com/eng/produ ... AP51_C-41S You really want the 51 and not the 10. One guy on Amazon successfully cools his 289 Mustang with it so it should be enough.
Most fans which shift anything like enough air are absurdly loud and to the most part unnecessarily powerful in normal, general use but you do really need that overhead in reserve. To this end I firstly focus on efficiency rather than outright power and cover as much of the matrix as possible, although the fan is around 150W. From my experiments the P6 rad is pretty effective, indeed as long as you keep moving a I proved a fan is unnecessary even in 34 degree heat. It seems to have specific problems with the tight packaging of the engine bay and the total lack of airflow when parked or in traffic. My solution is that often used in the 1980s and 1990s; use a two range thermoswitch. This feeds through a resistor to lower the power of the fan in general use and still has emergency "hurricane" mode to protect the engine in extreme conditions. It's also far more elegant and/or less leak prone than hacking hoses or sticking things through radiators. This is a standard M22 x 1.5 threaded item and there are HUNDREDS to choose from. Plymouth radiators did an excellent job for £20 (as they did 25 years previously to repair an earlier P6), so doing the job properly is cheaper and gives you more choice than the various kits you can buy.
Now the next issues I had were the themoswitch itself and the resistor value to control the fan. Reading up about resistor packs on various cars, it seems values vary between 1 ohm down to 0.33 ohms. Now the values I saw are all standard values in electronics which leads me to believe this isn't super matched to the application merely a balance of what is enough to cool the engine with the minimum of noise. From the figures the fan draws about 12A @ 13V, so about 1.08 ohms of nominal resistance and 150wattish output. So I bought a couple of 100W 0.47ohm resistors as a pair meaning I can get 0.235 ohm or 0.94ohms in parallel/series as well. Adding the single resistor makes the series resistance about 1.5ohms and drops the power to 112W - however the relationship between power and airflow and indeed the mechanical properties of the fan isn't linear so its more of a drop than you might imagine. It is MUCH quieter and cools well enough and I might try some other values out.
There is of course another advantage of this. The startup currents are very high, this drops the load from 12A down to 8.34A and it's much less of a strain on the thermoswitch relay. Even when it changes up to high speed as there is already back EMF the transient draw which can be over 25A is much reduced.
As for the thermoswitch itself I got this wrong to start with. I had a VW one with the ranges 102C - 91C and 95C - 84C. These are switch on and switch off points respectively. For the lower range 95 degree cut in is fine, but 84 degrees is too cool for an 82 degree thermostat as it's barely open. What tends to happen is the fan switches in and then hardly ever switches off. In the end I swapped this for a Volvo one (reference: Intermotor 50174) with the ranges 100C-95 and 95C-90C allowing 8 degrees over the opening point of the thermostat; 95 degrees pretty much being the "fully open" point of the stat. The car sits quite happily just over the 85 degree mark all day. If I park up in the sun I can't get the upper speed to kick in even in 35 degree heat after 30mins - good enough for me and it doesn't wake the neighbours. If you wanted it to run a couple degrees cooler then a Peugeot/Citreon one might be better as 97C-92C and 93C-88C ranges still allowing 6 degrees over the thermostat opening. However the P6 with a high pressure system can relatively happily work well over 100 degrees. Indeed later engines perhaps ill-advisedly work as normal at 110 degrees. I reckon 90-95 is fairly optimal.
What I will say is this is a huge load on the electrical system, you really feel the fan "rev up" with the engine as the alternator powers up. I have no idea how the guy with the 240W Kenlowe doesn't just melt his electrics and I'm not convinced that despite this power 13" will cool as well as this 16" given this covers more than 1 and half times the matrix area. You really absolutely NEED a 25amp separate fuse. I put mine on the always powered circuit as I'm happy to let the fan "run on" when stopped. Hopefully as well as avoiding localized boiling it might had I not solved this problem with an electric pump prevent vapour lock.
As a bonus, the engine is so much quieter without that mechanical lump spinning around. A large part of what I assumed was top end/tappet noise is actually a function of the engine fan spinning around. Perhaps it'll save the water pump bearings too. If you have a manual car consider it a cut-price flywheel lightening. It certainly seems a bit more "revvy".
Overall I'm not convinced of any economy or warm-up claims but what is nice is driving the car in summer, even in the heaviest traffic with both eyes on the road and not one on the temperature gauge. What might be a benefit come winter time is a bit more output from the heater but we'll see about that.
As I said this is a cooling project and not just a fan fitment and I also fitted the MGB expansion tank. Nice to know that top 2" of the rad is being used. I ditched the front number plate plinth as the Swiss plate is much smaller than the UK one it is modeled on. More airflow for free.
Overall the fan was expensive as you really need decent sealed bearings and Spal are about the best in the business. £120ish, the thermoswitch was a tenner off ebay, the resistors were £4 for two and the work on the rad £20. So allowing for cable, crimps, fuses and various nuts, bolts and brackets call it £155. What I would do differently is find an expansion tank with a coolant level warning and wire an indicator on the dash (maybe make it light up the choke warning so it looks original - I can even just use the "Otter" switch wiring) for extra peace of mind.
