Mario wrote
I see it is a 7 cylinder engine

I don't think so....to me, it looks like a twin row 14 cylinder
Pratt and Whitney 1830 Twin Wasp widely used on the C-47 during WW11.
Look at the number of spark plug wires at the front of the engine.

The R1830 Twin Wasp
The Pratt and Whitney R-1830 Twin Wasp engine was one of the most efficient
and reliable engines of the 1930s. It was introduced in 1932 with either a
6.1 or 6.5 compression ratio and 775 or 825 horsepower respectively, at
2,400 rpm. To reach its designed power the R-1830 needed the highest octane
gasoline available. Using improved fuel the R-1830 reached 1,000 hp and
later 1,200 hp. It has 14 cylinders in two banks of seven. The R-1830 was
used on B-24s, C-47s and the Grumman F4F-4 Wildcat, until it was phased out
by Grumman. Pratt and Whitney built 13,464 R-1830-90C engines for the C-47
aircraft. It was also used in a variety of British aircraft including the
Royal Air Force Catalinas, Short Sunderland Vs, Maryland bombers, and
Bristol Beauforts

Check the picture at this site...
http://www.maltaaviationmuseum.com/engines.asp

Bob Moore