Now that the basic form of the cylinder is established, I can begin to model the fins that cover the top of the cylinder. The geometry of the cylinder top is much more complicated than the sides, and will require a number of pieces and a fair bit of work. Based upon my photographic reference, it appears that the cylinder head is a cast piece, with smooth edges. I begin by modeling a single fin - since the fin has rounded edges I choose to begin with a narrow ChamferBox primitive. Once I have it sized to fit, I then convert it into an Editable Poly and begin to edit the object at the vertex level. I want the base of the box to flare out and give me a smooth edge where it meets the top of the cylinder, so I select and delete the vertices along the bottom, and using the scale and movement tools, I flare out the vertices along the new bottom edge to form a smooth curve (SCREENSHOT).
With one of the top fins built, I then clone it (select the object with the move tool and hold down the shift key). Since I wanted to reshape each fin to fit on the circular top, I made sure to select the "copy" option in the Clone Options dialog box (if I had chosen the "instance" option, any change I made to one of the fins would be done to all the fins). With the 4 new fins in place, I then edit each at the vertex level to fit on the top of the cylinder. Some of the fins need to have their ends trimmed back to match the curve of the cylinder edge (SCREENSHOT).
After a fair bit of work on the fins to get a smooth edge (editing at the vertex level) I have 5 fins that fit nicely. I group them and then use the Mirror tool to create another 5 fins, but now for the other side of the cylinder. I can see from my photographic reference that some of the fins will need to be edited once I have more of the top details in place, but for now these will suffice. I now do a quick render to check my progress (SCREENSHOT).
CYLINDER TOP INTAKE
The LeRhone engine has copper pipes that carry the fuel/air mixture from the crankcase to the cylinder head, and the intake valve is situated inside a small structure at the top of the cylinder. This structure is a combination of a rounded end, a boxy center section, and a two layer flared inlet end. To model it, I first started with a cylinder primitive and box primitive of exactly the same height and width. By cutting the cylinder in half, and joining it to the box (line them up, convert both to Editable Polys, attach them together, and use the vertex Weld command to clean up excess vertices), the front half was quickly done. The two level flared end was created from two Box primitives, modified to suit, and also attached and welded (SCREENSHOT).
After setting the new top intake in place, the top fins can be seen to be intersecting with it (SCREENSHOT). Based upon the photographic reference, there should be a space between them, so the top fins must be edited to clear the structure, again at the vertex level (SCREENSHOT).