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Originally Posted by curtis73
Designing a non-interference engine is a very difficult task to accomplish while maintaining a good compression ratio and not having very odd piston shapes and domes. One way of making an engine non-interference is by limiting cam lift to very low amounts and raising the roof of the combustion chamber so that they never would touch. But then you're left with a 8:1 CR and a cam with wimpy lift. The other way is to design most of your combustion space into the piston as valve reliefs. The odd shapes of the combustion space can limit power, and the tall profile of the piston can have negative affects on the rod length.
Instead the engineering choice is usually made to just design the bloody engine to run right and then design a timing belt that will last longer than the warranty  |
Or do what Saturn does and run a chain up to the OH cam.