Heat management was achieved with intricately finned heads and cam covers work. There are a lot of issues in those engines, which, over the years, people have worked around. Lubrication issues, in particular. When you suddenly want to do 12,000rpm you can’ t massage around a problem; you need to reengineer, fix it properly.
‘ Of course, we also had to engineer a valve train system that could handle the RPM. At 12,000rpm, you have no option; you have to have a lightweight valve train, which means valves that weigh far less than those big Porsche valves. And so, it’ s four per cylinder.’ The resulting heads are good for 12,000rpm, but to add a safety margin for other components in the engine many builders set a lower limit. Thornley Kelham’ s cars have either a 9000rpm or 10,000rpm limit, depending on capacity.
Not having to worry about creating a coolant jacket for the heads might seem like a benefit, but it was too much for Porsche to overcome when it was championing the air-cooled flat-six. Its four-valve flat-six heads, the ones it used in the 959, were watercooled, even though the cylinders remained air-cooled. The fact that Porsche couldn’ t solve the cooling issues didn’ t deter Swindon Powertrain. One look at the intricately finned cam covers compared to the functional, blocky ones of a standard engine, and you start to understand the extent of the heat management.
The new heads holding the four valves are, just like that of a factory air-cooled 911 engine, individual for each cylinder. There are tooling benefits to this – every single head is the same – there’ s also a cooling advantage with six individual heads, three on each side.
Spring 2026 The Engine Rebuilder 37