I Was talking to a couple of people that have had the 4 HP McDonald SPI engines and they said the engine has a thin copper ring then a outer gasket surrounding the five water holes and oil passage,
with rubber plugs around the 5 water inlet/outlet holes.
Apparently you can get by without the rubber plugs if a liberal rubberised gasket glue is used both sides of the gasket.
The copper ring takes up forming a good cylinder seal.
The bore diameter of this engine is 3 1//2 inches.
Still waiting on various contacts to see what gasket set I can come up with.
Worst scenario is I can procure the copper plate and make the copper ring myself, plus cut a gasket for water jackets.
Once I get it back to running again it will be a big clean up and paint job, then make a transporter for it.
Steel wheels are hard to come by, but I do attend a lot of sales and may get lucky.
I like working on the engines.
I did have the entire collection of 4Stroke Villiers all done up including the Mk414 the biggest Villiers made with JAP influence on design, It had a crank handle to start it.
I sold the whole collection to make room in my shed. Still have a few Villiers Left.
Cheers for now,
Grasshopper Max