To Vacuum Advance or Not to Vacuum Advance
I meant to mention one issue with using manifold vacuum. If the vacuum is a bit unstable, then the vacuum advance may be moving around as well. Especially with an automatic transmission, this can be annoying. It only happens when the vacuum moves the advance in the same range as the manifold vacuum at idle. But having been through that, thought it was worth mentioning.
Also sometimes people today have a hard time believing rich idle mixtures were the most efficient.
Here's a snip from a 1967 Chrysler Master Tech booklet on fuel mixtures and timing.
Later emissions set ups sometimes went leaner, sometimes richer. All depending on what they were trying to do. They played a lot of games with both mixtures and timing as they focused on different stuff and added items like cats and air injection.
I meant to mention one issue with using manifold vacuum. If the vacuum is a bit unstable, then the vacuum advance may be moving around as well. Especially with an automatic transmission, this can be annoying. It only happens when the vacuum moves the advance in the same range as the manifold vacuum at idle. But having been through that, thought it was worth mentioning.
Also sometimes people today have a hard time believing rich idle mixtures were the most efficient.
Here's a snip from a 1967 Chrysler Master Tech booklet on fuel mixtures and timing.
Later emissions set ups sometimes went leaner, sometimes richer. All depending on what they were trying to do. They played a lot of games with both mixtures and timing as they focused on different stuff and added items like cats and air injection.
