This is pretty much a cry out to those of you that know the ZZ4 crate
I'm looking for a possible fix as I have some valve noise and feel I've lost power
I don't know if there's something going on with my crate that I can fix, or if I should consider pulling it ....
This is my daily driver and money's not what it was when I bought the motor

The short story is;
-valve noise ( ticking ) from #8 exhaust that won't adjust
-vacuum is a bit erratic - 650-700 idle I get around 15 pounds, but it jumps up and down a couple pounds ( no vibrating needle )
-coming off a good run, the vacuum is good ( 15-17lbs solid ), then idle slows and vacuum is back to stumbling ( as is the idle )

The long story is;
So I have about 40K on this crate motor
I've been running it in my '78 GMC 1/2T with a 750ish Q-jet and it Aircares every year
I always wanted to put some kind of injection on it, but life got in the way

I originally ran this with a 5600 governor in the 700R4, but have knocked it back to about 4900 as I didn't like the city shift points with the higher RPMs

Right from the start it wasn't happy, and has been losing power as the years go by - had some valve noise I couldn't get rid of and it's getting noisier as time goes by - hear it all the time. Mostly it's just a ticking while driving by reflective walls and such ( originally thought it was due to the aluminum heads that let more noise through ), but the power it had is not there right now ( could be me )
And there's always been some noise from #8 exhaust, no matter how much I adjust the rocker

The vacuum is a bit erratic ....
At 650-700 idle I get around 15 pounds, and it's jumping a couple pounds up and down, but not vibrating
When I come off a good run, the vacuum is back to a steady 15-16lbs with a higher idle, then it starts to slow down. Then back to the stumbling

I have thought about changing the governor in my 700R4 to see what the top end is like and see if I get the power back that I once had, but I'm a bit nervous to blow it up if there is something going on

BTW, everyone who's listened to it can't nail down what the noise is ... hmmmm ....

Some specs are

Fuel is 91 Octane from Chevron Canada ( hopefully regulated )
I've checked my fuel tanks and there is no buildup of ethanol or other crud to speak of ( I worked in a rad shop for over 23 years and put drains in my tanks )
Timing is 11 degrees
Roughly once a year I run de-carb stuff through the PVC intake port @ the base of the carb when I get pinging uphill, but this hasn't happened lately
Wires are newer and resistance is below acceptable tolerances, but the brand quality could be better ( Aurora, just burning them out as I paid for them, then I'll put on the MSD ones I have waiting - I know, not the best, but better than the Auroras )
Plugs are MR43LTS and gapped to specs of 45
Replaced factory coil with Blue Streak ... no change
Replaced factory advance pot .... no change
Replaced factory pickup coil with Accel ... no change
Cap and rotor are Blue Streak, not that it should matter
Not sure what else you'd like to know ....

I know it's not a big help, but I bought 2 autometer analog air/fuel gauges, one for each header, that I haven't installed yet. Mostly due to finances ...
I was thinking that installing these would show me what is going on at idle and maybe I'd see a lean mix or something
Guess I should go get the bungs installed

I don't want to pull this anchor right now as it's still running every time I start it, and I know I should have installed the air/fuel meters before I posted this ....

Looking forward to your help