How to use 8-cores CPU as a single-core more (8x) powerful CPU?

Effectively, what you are asking, is how to take advantage of a multicore architecture without parallelizing code yourself. There are no ideal solutions for that, most likely, you will have to parallelize the code yourself manually; otherwise, you are bound to use a single core.

Nevertheless, there are a couple of things one can take advantage of:

1. If your algorithm happens to use other modules that already do the parallelization on their own, you might have to simply ensure the parallelization is used.
2. Look into some now-available semi-automatic parallelization modules, like Pydron.
3. Look into some area-specific automatic parallelization modules, similar to AutoParallel.
4. Consider automatic parallelization with @jit using Numba. Numba is pretty powerful but may require you to rewrite a lot of your existing code.

In conclusion, there is stuff to explore, but there is no such thing as turning multiple cores into a more efficient single core.