[German guy]

I bought and installed the FSI "zipper". I drove it for about 150 miles before putting my "Henry"(Made in Berlin 1930 Tudor Delux three door) to bed for the winter. Starts were vastly improved, running at all RPMs was immensely smoother. The final test will be when I install the new 6.1:1 head when my barn gets warm enough to work without freezing my fingers. FSI claims that the "zipper" is preset for up to the 6.1:1 advance curve. We will see in March.