360 timing

No Ted, the sparkport will not work for this.You must us vacuum from below the carb throttle plates. Sometimes you have to get creative in sourcing the vacuum.Sometimes you have to Tee into another line, such as the PCV hose,or the brake booster hose, or a choke pull-off line.Many manifolds have a plug somewhere that can be unscrewed and a vacuum nipple screwed in, in its place. The nipple can be sourced at any jobber.Whatever source you use, it must provide full vacuum at idle, and increase progressively as the throttle is opened. The sparkport takes its vacuum signal from just above the throttle plates. It is usually de-activated at idle, showing zero or near zero vacuum. Its signal also,is proportional to manifold vacuum and not usually the same as M-vacuum, at the smaller throttle openings.Eventually, as throttle angles increase, it catches up.If you like, you can put the guage on the sparkport just to see how it works. Then put it on the manifold source and compare.