Does anyone know how to identify the sizes of Quadra engines? I have been told the one I have is a Quadra.
There are no markings on it.

There are no markings on them. You can remove the exhaust and measure the bore to determine the CC.
You can also identify different sizes by the way the case is made. The 41 has a case that is halved horizontally while the 52 is vertical .

Post some pictures of it .

Quadra 35 has muffler held by one bolt, 42 has two

... also, Quadra 50/52 has side exhaust. 35/42 has it in the rear. There is a 25 and a 75 (or is it 70?), but they are kinda outliers.

Bedford

This is a Quadra 50

You can also see part exploded views on Bennet's site

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