Captain Obvious was talking about this the other day and he used a picture of my washing machine. 

 

So you have valve timing marks that show excessive slack. You have a poor running motor . Now you have valve train noise . Time to pull the timing cover 

Update:  Timing cover removed and awaiting kit. 

Anybody know how to diagnose a chain tensioner?  What else should I be on the lookout for in scouting for issues related to loose chain or bad liming?

@Patcon:  Interesting theory, about low oil pressure.  I get good reading on the dashboard gauge.  Is low oil pressure a known or common cause of loose chains?  

I dont know about common But oil pressure is what removes the slack from the chain. The tensioner aught to be a perfect fit in the bore. No slop

7 hours ago, Jughead said:

Update:  Timing cover removed and awaiting kit. 

Anybody know how to diagnose a chain tensioner?  What else should I be on the lookout for in scouting for issues related to loose chain or bad liming?

@Patcon:  Interesting theory, about low oil pressure.  I get good reading on the dashboard gauge.  Is low oil pressure a known or common cause of loose chains?  

Pics?

Update:  Waiting for parts to complete timing chain. 

In the meantime, Questions for the experts:

1)      The slot in the oil pump where the disti/oil pump drive shaft fits looks (to me) to be a rather wide gap.  It seems to be causing uneven wear on the the blade of the shaft.  I have a new shaft.  Should I also replace my oil pump? 

2)      My crank shaft key seems to be a little beat up (see pic).  I think it’s OK, but what ‘s the rule of thumb for know whether it needs replacing?  (I could see this potential causing a timing issue if worn…)

3)      Timing seems straight forward. Any “gothchas” I should be aware of that aren’t in the manuals?

a.       Both shaft keys up

b.       Bright chain links aligned to time marks on right side of sprockets

c.       I’m replacing chain, guides and tensioner.  Sprockets look fine.

d.       Disti shaft blade @ 11:25, small side to front

 

4)      Anything else I’m forgetting?

 

Here's an update on my Z, in case anyone's interested:  To summarize,  I chased a backfire/"frontfire" condition by replacing plugs, wires, distributor, timing chain, coil, points, ballast resistor intake exhaust manifold gaskets, head gasket, carbs.   I brought the head into AutoSport (Seattle) for a valve job & had the head rebuilt  and the intake & exhaust manifolds refreshed.  I even painted the engine block while I was at it.  The problem ended up being (drum roll...) 2 plug wires swapped at the rotor cap!   Duh.   (I give 99% of the blame to myself and 1% to the Haynes manual!) 

Anyway, the engine looks and runs great now,  and although I'm thoroughly embarrassed, I'm also extremely happy to have the Z on the road!  Thanks to everyone who pitched in to help, and EXTRA SPECIAL THANKS to Steve @ Z Therapy.  (What a great guy!) 

Along the way I had a lot of fun and learned a ton.  Now onto to the suspension...!

     

It's always nice when the solution gets posted up, even if it's a little embarrassing.

Glad you got it sorted!

On 12/22/2021 at 11:09 AM, Jughead said:

Anyway, the engine looks and runs great now,  and although I'm thoroughly embarrassed, I'm also extremely happy to have the Z on the road!  Thanks to everyone who pitched in to help

Although I didn't comment as I followed this thread for months, it seams like you have picked up a bunch of basic knowledge pertaining to you car.  Good on you!  Did you have any problems reinstalling the timing cover, in particular it's gasket, due to not removing your oil pan?  Also, your "under hood" and engine area is looking good.

@mayolivesThanks!  The oil pan gasket got jostled a bit on my second attempt at installing the front cover.  (I broke a cover bolt the first attempt.)  So far no leaking,  but I'll probably replace the pan gasket at some point anyway.  Right now I'm working on getting my choke cables adjusted...   Here's an engin pic from the other side (couldn't help myself).