OK, an update here. I finally got some dyno testing yesterday.. Learned a lot..! Unfortunately I had to make several changes at one time, thus it makes it more difficult to get to where I want quickly. New carb, with a totally different velocity stack design, and different jet designs, and some cylinder head changes. This is far less than ideal, where I like to make a single change at a time.

The first two dyno runs were aborted due to an extreme lean conditions. Made a 15 point main jet increase that made minimum difference. Quickly discovered an error in the main air correction jet. (new carb and old carb used different types of air jets and did not cross reference properly). Once the air jet was changed to a smaller size the jetting went rich, like it should. The air correction jet will be tested later to match that air jet to the needed fuel characteristics. Once we got our first full dyno run we noticed an increase in power at 6K, but slightly less at 7.5K. Aha..! This showed that we are either too long of too short on intake length. One of the changes with the new carb/stack set up is I went long (about 1.5") to start on purpose. Much easier to remove metal than add it on. Shortened the stack by 1/4" and the power peak started to move up, as expected. Ran out of time.. today will continue to shorten the stack until the power peaks, then starts to fall off. Also note that the 1/4" change in length required a main jet change. First change the length, then change the main jet. Each jet size (in my case) produces almost 1 H.P. So, it is impossible to make any meaningful judgement on intake length unless the jetting is also optimised for each change.

What is also interesting is that the more power we make, the cleaner the engine runs, emissions wise. And even more interesting is that the engine heat does not always increase with power increase. The change in engine heat may later allow for ignition timing changes as well. Currently I dyno with the timing slightly retarded until we get a good state of carb tune, then test for max power with ignition timing, while monitoring the engine heat. I finalize the ignition curve last. However I will likely do an initial ignition map later today, as the current readings tell me the timing is way off at some ranges. Being able to program the ignition curve in 500 RPM increments adds a lot of power at some steps.

Later..

Ron