I agree with your post that the differences in exhaust gas temperatures indicates that the hotter cylinders were running leaner than the cooler cylinders. Although the average A/F ratio was very close for the different manifolds, there were obviously some that had better A/F distribution between the various cylinders than others, based on the different exhaust gas temperatures.
I would also say that this has some effect on required timing, but I don't think it has as much effect as the cam, the compression ratio, and the chamber design. Just a guess, but I'd say any one of those factors could influence timing requirements over a range of 10 degrees, while A/F might influence the timing over a factor of 3-4 degrees. And so the differences in HP by optimizing timing for each intake (where one might require 34 degrees total and another might require 38) probably are not real significant.
As far as how much variation in A/F there is between cylinders, I really don't have a clue. What I need to do (thinking about future dyno projects) is to put a wideband oxygen sensor in each header pipe. Then we could correlate exhaust temperature to A/F, and get an idea.
By the way, the tool for doing that is already available, and I plan to get one before my next intake manifold comparo...
Jay Brown
1968 Shelby GT 500 Convertible, all aluminum 489" 1030 HP Supercharged FE
1969 XL Convertible, 460
1969 R code Mach 1, 706 HP 511" all aluminum FE, 10.457 @ 127.47, 2005 Drag Week Winner, Naturally Aspirated Big Block
