This actually happened about 3 years ago, but I was thinking of it because I was reconsidering how overlap affects a camshaft.
A custom cam grinder contacted me several years ago to see if I would be interested in getting cams from him. He said he would float me one if I wanted to try it and his cam would make 30 hp over whatever camshaft I had chosen. This particular Cleveland was my own engine and I had some extra time, so I had him grind a camshaft for it and gave him all the specs for the engine, including flow numbers, port volume, and even the specs for my own custom cam that I had ground for it.
Camshaft #1 was my cam. Camshaft #2 was his cam.
What's interesting is that the overlap was only 1° different from cam to cam. However, there was 28 peak hp difference between them and 10 average hp across the entire pull. My camshaft made 615 hp @ 8000 rpm and his cam made 587 @ 7800. The differences between the cams really aren't drastic. The lift is not too different, intake lobe duration is within 6°, LSA is within 2°, but his cam had a huge duration split on it.
On big intake port engines, overlap helps, and I generally have a very specific recipe I use for Tunnel Port heads and Clevelands. But what I was considering was it's obviously not the overlap number itself that plays the role, it's the culmination of the overlap, lobe separation, etc. This helps me in designing other camshafts, such as camshafts for street engines with vacuum requirements, because I can narrow down the amount of overlap to help vacuum, but still play with the other specifications to make horsepower.
FWIW, the 4V heads flowed 312 cfm @ .700" with nothing but a specific valve job and some new Ferrea valves. No port work.
So for the portion that applies to FE's....
I'm getting ready to finish up another TFS headed FE and I was able to build this engine very similar to the 447 that I have in the dyno section. Same cylinder heads, same intake manifold, same rotating assembly, same compression ratio, same everything.....what I am gonna change is the amount of duration split while holding the LSA the same. From what I've seen in the past, specific heads need a good bit of intake/exhaust duration split but a good A/B test is always worthwhile.
