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Additional Cooling for Bristol 401 Engine

OK, so the workshop manual says this engine does not need an oil cooler, and the fitted cooling system is adequate. Well, two successive summers on the WestRun organised by the Western Vintage Car Club proved otherwise as far as I was concerned. On a long fastish run, the oil temperature climbed over the 95C mark, and the oil pressure understandably dropped accordingly. To top that, we were stuck in Ballybrit race traffic last summer for a couple of hours with a boiling radiator. Being twitchy about losing an engine, and not willing to take out a new mortgage to have the engine overhauled, I decided to do something about it.  Now, you can speculate for as long as you wish about why the engine overheats. Just to put the usual issues aside, the timing was set up correctly, carburetion was perfect, and the standard fan was not slipping. The radiator seems not to be sludged up, it was (allegedly) re-cored in the not too distant past. Now old engines do sludge up their water passages (which of us doesn't as we get older). So my theory is that the heat rejection to coolant was down on the intended design, throwing an extra thermal load on the oil. Hence the rise in oil temperature. Conclusion- do something to take more heat from the oil circuit. And for good measure, fit an electric fan to deal with the horsey set in Ballybrit.

 

I will post more details shortly on the oil cooler adaptor fitted to the original Bristol engine oil filter housing. I also fitted a modern full flow filter to safeguard the engine further.

     
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The pictures above show the bits and pieces needed to mount the fan and oil cooler ahead of the radiator.  As you can see the brackets mount off the existing radiator fittings.  The air horns are displaced forward by the new assembly.
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The oil cooler is a Mocal 19-row type with 1/2 BSP fittings. The non return valve in the new oil cooler/filter adaptor prevents the oil draining back into the sump from the feed lines, but having the connections at the top of the cooler helps also. The fan came from a small Subaru and draws about 8 amps. It is controlled by a thermostat from the water temperature at the radiator top hose inlet. Any fan installation requires excellent shrouding if it is to be any way efficient. I was not entirely happy with the shrouding I fabricated, but it was the best I could do under the circumstances.