Cooling - Controlling water temperature

The introduction of the Cooper S proved to be a testing time for the Mini’s systems, but conveniently provide a guideline as to what the standard cooling system was capable of - that used on the ‘S’ was marginal to say the least!

It wasn’t uncommon for many S’s to spew water from their overflow pipes when ever it was doing anything other than a steady 70 miles an hour, over-heating eventually caused through water loss. Perhaps some deductions can be made from the following…

There are a number of elements involved in controlling water temperature. Some confusion over what to sort first when over-heating occurs leads to wasted time and money, and possibly terminal engine damage. Maximum power is usually generated from A-series engines at 70 – 75 degrees C (160 to 170 degrees F). The main problem with this on a road car is the oil’s unlikely to get hot enough for maximum performance – the results outlined previously.

Cylinder head - Min Tec head range

I'm often asked about the range of cylinder heads I do for Mini Spares/Mini Mania, so here's the low-down…

Although the following range of heads accommodate specific fitments - like pre-1992 where by-pass hoses and heater take-offs on the clutch end of the head are used and post-1992 where neither of these exist, and on SPi (single point injection) heads where they don't usually have a threaded hole for the temperature sender - in reality it is easy to convert almost any of them to fit any other engine since holes are easily blocked off - or by-pass hoses not used, water pumps blanked off and drilled thermostats fitted (see articles on cooling/engine transplants). A list of which is what and what to do to each to convert is at the end of this article.

For more in-depth descriptions of the head specs, see article 'Cylinder head - About Min Tec Heads' - basically the valve sizes used have been decided on after extensive and in-depth flow test...

Lubrication - Temperature critical

The correct running temperature of the oil is perhaps even more important than the water/coolant temperatures - so let us consider how to control them.

Mainly because it seems to be the most misunderstood of the whole process, and oil cooler fitment almost a reflex when over-heating occurs where a tuned engine of any type is concerned. And in many cases on standard production road cars for that matter.

Almost since the appearance of the immortal Cooper S, fitting an oil cooler has been the essential thing to do to any tuned Mini without any comprehension why. The original fitment was necessary because oil and bearing technology wasn't too advanced. Asking an oil of yester-year to cope with lubricating an engine at racing speeds, and a gearbox pushed their performance to the edge of their all too narrow capability, so extreme control over their working environment was essential for reliability. Hence oil cooler fitment.

Cylinder head 2022