[May70]

How about some inputs on this.... Maybe years of experience and what ive got here might light a bulb for someone.

I did some searching for more info on using vacuum to diagnose issues. Everything I have read only lists one reason for vac going to zero. But the vacuum shows some fluctuation before dropping toward zero which got me thinking.... I know the exhaust is not blocked so maybe that initial fluctuation means something...

Looking at the second video I posted ( Post #163) with the muffler off ( I got the same readings with exhaust off at the manifold); It holds a relatively steady 22 at idle. There is no fluctuation until accelerating, when it decreases to 20 then increases to 23 after that point it drops off to zero. I see two distinct patterns first a fluctuation off idle from 20-23, then with continued acceleration a drop off towards zero while noting the engine sounding like its dying off. With that in mind, I found this article out of a pop mechanic magazine which gives the best guide ive been able to find.

Looking at Case #5 in the picture from pop mechanics: Normal and steady reading at idle, but vibrating reading at high speed - weak valve springs. Does this explain the first pattern of fluctuation between 20-23?

I found another guide on another forum that indicated similar (second pic).

Could it be possible that an extreme case of the valve springs being weak cause essentially a complete loss of power/vac with acceleration? If the engine is dying out, wouldn't that cause the vac to go to zero as a result?

Also looking at #1 and #2 on the pop mechanic article, to me that is saying I do not have an issue with either my carb settings at idle or the wrong timing. Is that a leap too far?