I say it has better throttle response (very slight difference) because vacuum is best when you can get the engine to run as high as you can per as little throttle opening as possible to still hold that rpm. Example is when you are doing 45 mph down the road and down shift into 2nd and take your foot off the accelerator. The rpm raise up and the throttle plates are closed which creates a high vacuum condition. Same at idle, the vacuum will be the greatest with the engine running at idle with minimum throttle opening. The vacuum advance does exactly that at idle, it raises the rpm while not moving the throttle so you can actually obtain the highest (throttle-rpm) ratio. Because of that it creates a stronger vacuum signal at the carb and will give a better response (again very slight) because you are keeping the throttle plates closed more than with the ported source. After the throttle plates open and ported kicks in the effect are the same because the timing is the same both ways. I would say just off idle response is just slightly better. Mostly just an idle thing though.
|