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High-efficiency four-row radiator for the V8
Gordon Hesketh-Jones reported in late 2008 that he was installing a modified radiator to his well campaigned V8. Now following a trip to Spain, he provides feedback on how it has performed. (Feb 09)

If you scan through the V8 Workshops Notes Contents List you will see that there have been more than 20 Notes on overheating, cooling and radiators, some going back as far as 1979. There have been more recent contributions by Roger Parker, Bob Owen, Bill McCulloch and myself, but the problem has not been solved simply because the engineers at Abingdon were faced with a Mission Impossible - to shoe-horn a V8 engine with more than twice the volume and heat-generating capacity into an engine bay previously used for a small four-cylinder engine. In addition, these engineers had to produce this new model at maximum speed and with minimum development time and cost.

Some years ago we drove down from the Danish border to visit Allan and Eva Doyle near Nuremberg, a distance of nearly 500 miles. For the whole day the large temperature gauges on the motorway service stations showed the ambients as being from 25°C to an eye-opening 43°C, yet whilst our V8's temperature gauge rose to around a reasonable 100°C (i.e., in line with the ambient increase), we had no engine worries and the petrol consumption was 32/34mpg. To me this proved that with a decent flow of air through the radiator, the engine would be properly cooled. However, as we all know the problems arrive not on fast driving with plenty of airflow, but when we are trickling along in traffic-clogged towns and cities.

Many of us have approached this problem with a variety of solutions but none with perfect success, so I decided it was time to do a bit of lateral thinking and tried to think about which other vehicles have powerful engines, but virtually always travel at low speeds. The answer (to me at least) was that tractors, earth-movers and JCBs are in this category so I contacted our local radiator supplier in Plymouth - "local" means less than 100 miles when you are in West Cornwall. They understood the problem and told me that
G M Radiators near Glasgow make these specialist radiator cores. After discussions with them the proposal was to make a 4-core unit instead of the standard three cores, with 11 rows of fins per inch instead of 7. Crucially, the tubes would be 13.5mm O/D (2.2mm wall thickness so 9.1mm I/D) compared to the standard tubes which are 9.3mm O/D (4.9mm I/D). These new tubes therefore have an internal cross-sectional area of 14.3 mm² compared to 7.69 mm² for the standard tubes, i.e., virtually double the cross sectional area leading to faster water flow through the radiator. The tubes are 355mm long - the same as at present so no change to the height or depth of the header tank and the bottom tank - and, crucially, the top and bottom hose connections.

Being 4-row, the radiator is approximately 25mm deeper front to back so obviously is a tight fit in my crowded engine bay. At the front there is a gap of approximately 8mm between the valance and the front of the core, whilst on the engine side there is around 10mm between the core and the anti-roll bar. The core is still approximately 25mm clear of the fan pulley. The brackets, header tank and bottom tank off my old radiator were retained then welded/soldered onto the top of the new core - leading to the "shoulders" approximately 7mm wide shown in the photo. As the radiator intrudes into the engine bay, the top and bottom hoses had to be shortened by around 15mm to avoid creating sharp bends.

I measured the coolant capacity of the standard radiator at 3.1 litres and the revised version at 4.0 litres so there has been a useful improvement. From my mileage of around 4,500 so far, I have noticed that the heat output from the cabin heater has increased dramatically - possibly due to the fact that the coolant now circulates through the system far more quickly with the larger-diameter radiator tubes; from what I can recall, most of the coolant flow passages in the engine are at least 10mm I/D so the standard radiator tubes of 4.9mm I/D would have presented a restriction in the water-flow speed. This improvement in cabin heater output was most welcome for this Winter's trip to France and Spain.

Does it work? Well, we crossed the dreaded Boulevarde Periphique in the evening rush-hour (45 minutes of stop-start inching due to ferry delays); the ambient was around 12°C and the V8's temperature gauge rose just slightly - but not enough to bring the fans on!

At around £265 the price is virtually three and a half times the cost of the standard MGB Hive V8 version but only slightly higher than the Hi-Flow MOSS MGB versions. As it does the job well, I am not complaining! If you want to follow this route - ask your local radiator people to contact G M Radiators - who only supply to the trade. http://www.gmradiator.co.uk/
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