Sunbeam 1000hp Blog – Part III

Posted  05.04.2017
Comments  (00)

Reaching the 90th anniversary of Major Henry Segrave’s 1927 World Land Speed Record on 29th March, there has been a huge amount of interest from across the globe in the National Motor Museum’s Sunbeam 1000hp project. With the aim of preserving this incredible car for future generations, the museum engineers are battling to bring one of its colossal V12 engines back to life in this milestone year.

A fork-lift truck was required to lift each massive V12 engine

Corrosion had attacked the engine’s internal parts, such as the crankshaft shown here

Sunbeam crankshaft
Great care was needed when lifting the crankshaft out of the engine’s crank case


Once the rear engine had been lifted from the car’s structure with the aid of a fork-lift truck, the strip-down could begin. The manifolds and carburetors were removed, followed by the long tubular ‘boxes’ that house each of the four cam shafts on the very top of the engine. The two Sunbeam Matabele V12 aero engines were in a bad way after years of inactivity, having suffered due to severe internal corrosion.

Each engine is fitted with four alloy blocks, which locate three cylinders each. These blocks were unbolted from the single crank case and each piston withdrawn from its cylinder. As there are no separate cylinder heads, this is the only way to access and withdraw the valves. Next, with the pistons and connecting rods removed, the huge crankshaft was carefully lifted out of the crank case; this was sent to a specialist for work, along with the connecting rods.

Engine parts were immersed in cleaning solution to remove decades of grime

Sunbeam engine block repairs
Sophisticated laser welding techniques were used to stitch repair damage to the alloy blocks

Sunbeam engine block
Damaged threads for the water jacket side plates were re-tapped on all four blocks

The blocks and the crank case were soaked in a bath of powerful cleaning solution, to remove the built-up layers of old oil, grime and paint. This exposed small but potentially calamitous areas of damage to the crank case and one of the blocks. To rectify this, these were sent away to be professionally laser-welded, this cutting-edge technology being ideal for intricate repairs where strength is critical.

The cooling system employs a water jacket in each block, which keeps coolant circulating around the outside of each cylinder. The flat plates that enclose these water jackets looked fine from the outside, but inside had been ravaged by corrosion. New plates were cut from flat alloy, with their snapped and corroded fitting studs painstakingly drilled out and re-tapped.

Sunbeam con rods
Built to handle 435bhp, the original con rods are robustly engineered and will be reused

Sunbeam 1000hp pistons
The huge pistons were painstakingly cleaned; new piston rings will be made to fit them

Magneto testing
The magnetos produced a good spark on the test bed, but were restored to ensure reliability

In addition to the known corrosion issues, the engine had suffered due to the decay of its ancient oil, which had turned into a thick, glue-like substance. As a result, perseverance was required from the engineers to make the piston rings relinquish their grip on the pistons. Almost all of the original piston rings were recovered, but a new set will still be created to replace them.

While every component was being fastidiously checked, cleaned and prepared for further service, attention was also turned to the magnetos. Each magneto generates the spark required for ignition and distributes it to the spark plugs, with four magnetos fitted to each Sunbeam Matabele V12 engine. Hooked up to a special test bed, they were found to still be in good health. However, it was deemed prudent to have these components rebuilt by a specialist, to ensure that they are reliable.

As work continues and several components are sent to receive specialist attention, in the build-up towards the final reassembly of the engine, the goal of hearing it run again doesn’t seem so very far off.

Don’t miss the next Sunbeam 1000hp blog post, as the rebuild of this extraordinary engine nears completion.

Categories:  Archived