Vacuum PSI Reading points to burned or leaking valve?

[Jack]

Did vacuum test today.
At idle it jumps back and forth from 19-20" Hg at regular intervals.
According to a document about vacuum readings pointing to problems., this could be caused by a burned or leaky valve.
It never had a valve adjustment, car only had 3,000 mile went I got it now it has 37,000 so yes it certainly past that time.
Was wondering if that 1" Hg jump could be caused by anything else?
Also can the valves be inspected "enough" with the valve cover and air horn removed or would complete removal of the head cover be required to fully inspects the valves?
Thanks in advance :)

[DMCMW Dave]

Did vacuum test today.
At idle it jumps back and forth from 19-20" Hg at regular intervals.
According to a document about vacuum readings pointing to problems., this could be caused by a burned or leaky valve.
It never had a valve adjustment, car only had 3,000 mile went I got it now it has 37,000 so yes it certainly past that time.
Was wondering if that 1" Hg jump could be caused by anything else?
Also can the valves be inspected "enough" with the valve cover and air horn removed or would complete removal of the head cover be required to fully inspects the valves?
Thanks in advance :)

It's caused by your Odd-Fire engine.

[Jack]

It's caused by your Odd-Fire engine.

Good to know.
Thanks

So at least I'm back to "just" needing the valve adjustment for 30,000 tune up.
Plus I got to change the timing cover gasket, got a every small leak at one bolt...

[David T]

I never liked using the vacuum gauge to diagnose valve problems. Do a compression test, preferable after you check the valve adjustment. Also change the O2 sensor and reset the Lambda counter. Clean and regap the spark plugs or replace them. You should also check the timing and the vacuum and mechanical advance. If you have a dwell meter you could also adjust the mixture (if it needs any).
David Teitelbaum