STUART LIGHTWEIGHT PETROL ENGINE BUILD

Part three by Jason Ballamy

The remaining bit of steel for the head had a spigot turned on it that would fit into the cylinder liner, then holding by this spigot the shape of the head was formed. I drew it out in Alibre and took offsets at 0.025" intervals which gave the basic shape. This was then refined with hand graver and files. The hole for the plug was also tapped M10x1 at this stage.

Then the head was bolted to the mill table and dialed in.
Following which the four stud holes and one water passage were drilled and then deeply counterbored.
A few stub ends of steel were then soldered into these counterbores to form the stud and water pipe bosses.
After a bit of a clean up the bosses were machined to height and the holes taken to finished size.
I also cut some slots into the head to match those in the top of the cylinder, these should allow some water cooling of the head.
The last jobs on the head were to shape the underside of the spigot to match the shape of the top of the piston and use a bit of JBWeld to form some fillets around the bosses to get that cast look.

A 3" dia piece of 6082 aluminium ally was held in the 3-jaw and a start made on the crankcase cover. After facing off it was bored and counterbored for the bronze bearing then the outside diameters were taken to size.

It was then reversed in the chuck, the bolting flange brought down to thickness, a spigot for the timing bracket turned and as much waste as possible removed between the two.
It was then over to the mill to drill the eight stud holes and mill out more material to leave four stiffening webs. After machining these were attacked with the Dremel to get them looking more like castings.


See Part one here  part two  part three  part foupart five  part six  part seven