Man your motor sounds really good. Surely that is not stock. My stock motor is so much more silent.
I will do as you mentioned with the choke on the carb and see what effect that has.
My timing is not wrong a I did have it checked with a timing light and we had it set originally at 4*, but then we played around a bit over a time going in increments all the way to about 12*. The miss never went away.
You know I was on another forum and a retired mechanic that worked at the GM factory in South Africa, said that the L6 250 had much lower vacuum than other engines. But this contradict what you said above. I don't know if he has tested it on his motor as he also has the same motor as mine.
But you have the gauge connected to your motor and you know its reading much higher than what I am getting. The only question I would ask is did you ever test the vacuum when you had the original Monojet carb, which is what I still have on mine?
Thanks again for the response much appreciated.
