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Improved cooling with the MGBV8
Gordon Hesketh-Jones (Harvest Gold 1904) from Cornwall has done over 200,000 miles in his V8 and has suffered from overheating in hot weather. He has solved those problems but still suffered from dreadfully hot feet inside the car! Here Gordon describes the measures he has taken to improve the cooling of the engine in his MGBGTV8. (May 02)

The cooling of the engine in the BGTV8 could only at the best be described as "marginal" even when the car was first built, with new parts and factory tolerances. Now that the BGTV8s are some 25 years old, things are different. Having covered over 200,000 miles in mine in the past 15 years I have had plenty of time to reflect on the overheating problem and its causes, and have also experimented with cures. So I hope that the following comments will be useful.

To start with the basics, the engine is cooled by the thermo-convection of hot water into the radiator where the through-flow of air reduces the water temperature ready for re-circulation to the engine water jacket by the water pump. The velocity of air-flow through the radiator will be a function of the system resistance - if the air can escape freely from the engine bay, then there will be a high-speed airflow and excellent cooling. Now the design characteristic of an axial fan, whether electric or belt driven, is that it will deliver high volumes of air-flow but only against low back pressure so the standard fans fitted to MGs are therefore ideally suited to cooling the MGB and MGC which constitute low-pressure cooling applications. Anyone who has looked at the V8 engine bay however will immediately realise that one almost has to feel sorry for the air as it desperately tries to escape from the over-crowded engine bay! Obviously and visibly the V8 engine bay represents a high-pressure resistance to the air-flow so the design characteristic of the axial electric fans means that they are basically unsuited to dealing with it.

On the basis that I feel we are starting from an unsatisfactory position and that all the correct checks on radiator efficiency have been carried out, I offer the following suggestions on how to reduce the anticipated overheating, arranged roughly in ascending order of cost:

Thermostat modification - take out the thermostat and remove the spring and working parts, then replace the front disk; this guards against thermostat failure but also slows down the water flow rate so as to give the water a better chance of absorbing and carrying away the engine heat. If the thermostat is omitted completely, the water flows too quickly to pick up the right amount of heat from the engine in the Summer, whilst in the Winter the engine will take far too long to reach the optimum operating temperature.

Remove any RAC/AA/MGCC badges from the front grill; two of these plus the V8 badge can disturb and reduce the area available for air-flow through the radiator by between 15% and 20%. If badges are essential (including the V8 badge), then position them behind the over-riders. Editor: Note there is now a smaller V8 Register badge available as an alternative for the MGBGTV8.

Use your heater - if you see the temperature gauge rising to unpleasant levels, promptly switch on the heater fan, turn the windscreen heater control to maximum heat and open the sun-roof and/or windows.

Fit a an override switch in parallel with the fan thermostat (mounted on top of the engine, near to the alternator) so that the radiator fans can be switched on manually; as a standard practice in warm weather I switch the fans on as soon as I enter a 30mph area. The switch, (I used a heater fan rocker switch which also looks the part), has to be wired to connect to earth. The addition of a warning light on the dash to show that the fans are switched on is a useful comfort factor.

Fit a yellow V8 fan blade or alternatively a standard MGB fan blade onto the existing boss at the top of the alternator drive-belt system, preferably with a guard as it will be rotating when-ever the engine is working.

Replacing the V8 water pump - I find that the tips of the impeller blades on the water pump wear quite

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quickly so that the water is not being circulated as efficiently as it should be. On high annual mileage cars I recommend changing the water pump every 25,000 miles and the improvement in cooling can be easily seen at each change.

Change the existing 3-core radiator to a 4-core unit thus allowing more water to be cooled by the air-flow. As far as I know there are no 4-core radiators available off the shelf but a local radiator manufacturer can easily produce one using the header tank, base, and side frame from the standard unit.

Make up brackets and move the oil cooler to a position underneath its existing position but mounted centrally behind the apertures in the front valance as on the R/B V8s; the oil will still be cooled quite adequately but if you are worried then move the number plate an inch or so higher. Moving the oil cooler will give a 20% to 25% increase in the air flow through the radiator. It is not too difficult to re-route the oil pipes for the cooler and the standard oil pipes for the R/B V8s can be easily obtained and used.

Fit louvres to the bonnet as on the Morgan Plus 8. I saw an MGBV8 Roadster Conversion at the Abingdon Show some years ago with two sets of louvres up the whole length of the bonnet as also seen on the V8-engined Morgans.

Improved cooling fans. Some fans are available from America using brushless DC motors with fan blades of a similar diameter to the standard fans, but with 6 blades instead of 4. The blades on these American fans are of a much better aerodynamic shape also they rotate faster that our standard brushed fans so give greater cooling. The brushless electronic DC motors offer virtually infinite life and minimal current drain, compared to the standard fans which in my experience fail quite regularly and which draw 12 amps when running. Incidentally these American fans are technically also a much better design than the RV8 fans.

Fit the stainless steel exhaust manifolds from the RV8 which exit via the side walls of the engine bay thus taking the heat away more quickly, whilst the clearance holes for the manifolds provide additional escape paths for the air-flow into the low-pressure area around the front wheels. The standard manifolds (a) are of a poor shape, designed purely around the available space in the MGB engine bay rather than focussing on engine efficiency and (b) are made of cast iron which acts as a heat soak thus radiates heat very efficiently! The RV8 manifolds join together near the gearbox with a balancer pipe, then a single pipe goes to the rear silencer so there is no need to alter the fuel tank position. This modification is very effective but is more expensive, as the manifolds plus exhaust cost around £470, to which has to be added the cost of cutting the holes in the inner wings, welding on the surround plates then respraying the engine bay before fitting the system.

Following a recent drive to Sicily in May 2002, then touring the island in temperatures of 30oC, I can confirm that the RV8 manifolds are the complete cure to the overheating of both the engine and the driver's and passenger's feet! Obviously in these temperatures I still switched the fans on (using the override switch) for traffic delays or for climbing serious hills. The only time I had to resort to switching on the heater as well was when we climbed a steep mountain pass with 30 to 40 hairpins in the midday heat.

Two other points - in hot weather the MGBV8GT footwell with the standard exhaust manifolds always gives the driver and passenger over-heated feet. To reduce this discomfort I recommend total insulation of the gearbox tunnel, the floor, and the engine fire-wall with a flexible aluminium/mylar heat insulation sandwich material obtainable from specialist suppliers such as Agriemach (Tel 01342 713743). Agriemach also supply a special asbestos-type material for wrapping around the exhaust manifold which is very effective. Conversely in a spell of really cold winter weather the warmth inside the cabin can be greatly increased by removing the steel cover from the brake and clutch cylinders - provided you are sure that there are no leaks from the exhaust manifolds etc!

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