Yep.. Thats what happend.
Your tensioner popped out.
Ive tried using a block of wood in the past and you usually have a 50/50 chance the tension will be enough to hold the chain once you remove the Cam gear during, say, a headgasket or head replacement.
Its a pain, but just get a timing cover gasket kit, and it will give you a new crank seal, a waterpump gasket, and the 2 gaskets for your timing cover itself along with an oilpump gasket.
I use Hylomar gasket dressing (great stuff, and available at any autoparts store) to help hold the gaskets to the block during install. Be sure to coat it on BOTH sides it helps stuff STAY as you work.. DO NOT use Silicon. Its not needed on this area of the timing cover and the gaskets will do the job just fine with the hylomar coating.
But, on the pan, most of the engines just used RTV sealant, (silicon) and you will need to scrape off the old crap (be VERY careful you dont drop scraps into the oil pan as a small amount will be exposed once you remove the timing cover!) Place a Rag in the area where the oil pan is (be sure its clean) and dont push it in so far that you get it stuck down in the pan. (obvious advice
Be aware that you WILL get coolant into the oilpan. CHANGE YOUR OIL! before you start the motor.. this is CRITICAL!!!
Also, the timing needs to be set at TDC (top dead center) when you do this stuff anyway, but make sure that you keep it there when you go to reinstall your Oil Pump and distributor.. Its might take you a few tries to do this, so be SURE you mark your distributor rotor position as accurately as possible where cylinder 1 fires.
IF you set your engine to TDC, and you didnt disturb your Position of your chain from TDC, then all you have to do is simply mark the rotor to a spot on the housing of the distributor. That will make sure you get TDC on Cylinder 1 postioned and the oil pump will engage into the distributor shaft.
Since the Oil pump and Distributor share the crankshaft drive gear, you will need to be sure they are set correctly to get your timing right.
Have a Timing light available when you get it back together, and be sure that your Timing is correct.
If you place your Timing Light on Cylinder 1, (the front most cylinder) and the engine either doesnt run or run right, or you cant get the timing mark close enough to run when turning the distributor within the bolt range (the bolts you use to lock the distributor down) then you might have the distributor off a tooth.
You cant just leave it that way. LOL.
A Good service manual (haynes for example) will help you along.. But these are just tips from a man thats done several Z24's over the years.
Oh, by the way.. If you are in there anyway, Might be good to just get a timing chain and gear set too (will come with a new tensioner and the slipper, and guide.
that way you wont have to do this again anytime soon. About $60-$70.00 for a set, and about $10-$15 for gaskets.
Tip for the tensioner.. The Timing tensioner at the crank is simply bolted on with 2, 10 MM bolts.. be sure they are TIGHT, but BE CAREFUL.. they can SNAP if overtightened. Not to scare you, but be cautious.
Ive never snapped them yet, but 10mm Bolts usually cant stand more than about 10 Ft lbs, so if you go over that, it will likely buy the farm. (use manual for specs).
Also, when you install the timing slipper (it bends with the chain and the chain slides over it) is mounted on the left side of the crank when you look at the front of the engine).. It also uses 10MM bolts, when you tighten this down, PUSH The Slipper as hard as you can against the chain and then tighten the bolts!.. This will help prevent the chain slapping once it breaks in.
On the Guide side (right hand).. just be sure that its mounted correctly, and tighten the bolts down. (also 10MM). You dont need to push anything.
Good luck, and RECHECK your work.. Dont assume.. Recheck. Period. You dont want to do this stuff again anytime soon. LOL