A tale of three engines. This is how I got the kit, with the engine already built up:

There are a few things going on here. Clearly, three pushrods have gone missing. Also, the builder has left lumps of feed sprue on the end, which meant the engine didn't fit inside the cowl
I chopped the pushrods off, I didn't like the result much:

The cambox isn't really much like a Clerget 9Z. So I ordered a WNW Clerget, which arived today (I got mugged by Royal Mail this time)

A much finer engine. Only....

It won't fit inside the Roden cowl. Checking the dimensions, the outside diameter of the cowl is fine, the walls are much too thick
I didn't want to chop the WNW engine about, I did consider using the WNW 9Z cambox on the Roden engine, leaving me with a WNW Clerget 9B for future projects. I also considered vacuum forming a new cowl from thin styrene that would clear the rockers on the WNW engine
Then I remembered I had a HobbyCraft Clerget from a stalled project:

And it fits the Roden cowl!:

So, I'll use that. That leaves a WNW Clerget for future projects and a Roden cylinder set for the parts bin
Richard