Engine Ported vacuum question

[Kruzkraft]

I’m new to the 225 odd fire and and need some schooling. I was checking the tune on a new to me 1970 CJ5 with the original and stock looking V6. When the engine was cool the ported vacuum was pulling a steady 19lbs, but as it came up to temperature vacuum dropped to 5lbs.
The carb looks original and manifold vacuum remained at 19lbs.
What I’m I missing?

 

[Patrick]

There shouldn’t be any vacuum when your engine is idling on that specific port. There will be vacuum anywhere off idle. You might be looking at the wrong port.