One fascinating aspect of the Daihatsu C-Series would be noting the apparent similarities between it and the Toyota A engine 4-cylinder, which is not surprising given the ties between the two companies (along with the belief by some that Toyota either drew inspiration from or pretty much copied the Cosworth BDA engine for the A engine).
Both engines appeared roughly at the same time in 1977-1978, both have cast-iron blocks with alloy-heads and belt-drives, the 1-litre Daihatsu CB and 1.3-litre Toyota 2A share the same bore with Daihatsu even making use of Toyota’s lean-burn design system. Would it be accurate to say that such a relationship does indeed exist between the 3-cylinder Daihatsu C-Series and 4-cylinder Toyota A engines?
It also brings up the question of whether the later Daihatsu E-Series 3-cylinder was derived from any other Toyota engines (if the E-Series is completely unrelated to the H-Series), since while Daihatsu specializes in smaller engines it is difficult to believe they are complete clean-sheet designs.