After rallying my 1915 Blackstone hot bulb oil engine for a couple of years, I decided that it was time to completely strip it down and do a full refurbishment job on it.

I purchased the Blackstone as a restored runner in April 2013. It was complete and mounted on a 6x4 trailer, and I displayed it like this for a couple of years before deciding that it was time for a freshen-up.

After removing the crankshaft and flywheels I found one of the main bearing housings on the block was broken in two places. So my first job was to buy some Ni55 x 2.6mm cast iron welding rods and weld it up, which fixed this issue. 

Next I removed the sideshaft which allowed me to see that the bearings needed to be rebushed. I have an old mate Bob, who is a very good machinist (he can fix the impossible) so I took the bearings to him so he could make and fit new bushes. New valves and guides also needed to be replaced and Bob made and fitted the new guides to suit the new valves.

The 4½” bore was in good condition, but the piston ring grooves were found to be badly worn. A new set of piston rings were ordered and the grooves on the pistons were machined to suit. 

To make it easier to move the flywheels around the workshop, I made up a jig to hold the flywheels on a trolley, on which they would stay throughout the preparation and painting processes. 

The flywheels are 30 inches in diameter with a 3¼ inch face, and I spent weeks sanding them back to a smooth condition. Once I thought they were of an acceptable standard, they were taken down to my brother Glen, who is a professional spraypainter in Canberra, ACT, to be primed and painted. Glen took one look at them, said “Not good enough”, handed me some wet and dry paper, and told me to start again. While I was preparing the flywheels, Glen started work on the base, and the cylinder housing. It took close to 12 months (part-time) to have them ready to be primed and painted. We had a couple of goes at matching the correct colour from a paint chip taken from around the cylinder housing, finally deciding to use a flat 2 Pac paint with a clear coat over it as it is more durable.

Finally, after days of rubbing back, it was time for the primer, top coats, and the clear lacquer and, of course, it needed to be rubbed back between all coats.

While my brother was doing the painting including the light green pin-stripes and all the letters, I was preparing the head and all other spares to be ready for priming and the top coat. A new water tank was constructed and painted as the old one had some rust holes in the bottom.

Next on the list was to give the trailer a rebuild. Knowing that I wanted the engine to be covered while travelling, and at night on the rally ground, I set about constructing a light-weight removeable frame with three cross braces over the top. This was then taken to A1 Marine Auto at Mittagong, who fashioned a cover out of polyester-backed torneau material. It was at this point that it was time to remove the old floor which had started to buckle from being left out in the weather, and although it was structually sound, I took the opportunity to add a couple more steel cross bearers to help with supporting the weight of the engine. Once I was happy with the framework it was sandblasted before being repainted with 2 Pac paint. 

I then installed a new Pacific Jarrah hardwood floor, which was  professionally sprayed by a very good friend John, using marine lacquer which is hard-wearing and weather resistant. 

The trailer with the engine mounted comes in at 860kgs with approximately 10% of this weight on the drawbar.

After a few years of work, at long last it was start-up time. I heated up the hot bulb and it started very easily, but all it wanted to do was keep revving its little heart out.

After re-setting the valve timing and checking the fuel settings, it still continued to run too fast, so it was back to the drawing board. I thought, there’s only one thing left...the governor, so I decided to remove it, and I discovered that some of the 2 Pac paint had seized up the pins on the governor weights. This was quickly rectified and at the same time, a new spring was fitted as the old one was getting very sad. After these minor adjustments it ran very well at about 200rpm.

The Blackstone 1915 Hot Bulb Oil Engine. Serial No. 1751. built August 1915. The engine is started by heating with a blow lamp which is turned out after half an hour. Power output is 3bhp @ 300rpm. It is now running at 200rpm. It operates on household kerosene. The engine was found in the out back of NSW, driving 3 stand shearing plant. It has been rebored and sleeved back to standard size 4½ inch.

Its first outing was at the National Rally at Hamilton, Vic, in 2017, where it performed and presented to my satisfaction.

I have since made a modification to the water tank, as I found that while running the engine, the water in the tank was getting hot in the top but remaining cold down the bottom. This was also the case with the cylinder housing which had a definite temperature difference between the top and bottom, an issue that I believed would not be good for the long-term operation of the engine. To overcome this issue, I had  a smaller stainless steel cylindrical tank of 8” diameter fitted into the internal of the original tank. This has reduced the tank capacity down to 45 litres, but it has more importantly eliminated the temperature difference in the housing.

I would like to thank my brother, Glen, for his supervision along with his first class paint job. And to all the others that helped me, Bob the machinist, my brother, Laurie, who supplied and fitted the decals, and my son, Stephen, who helped me with the trailer. Thanks also to my good friend, John who, with his expertise, painted the trailer floor. Great work. 

*John Green