First, let me say smart move not trying to restart the engine after a massive backfire.
More specific info about your engine would probably be helpful (year, last time valves/cams/timing chain adjustments were done, carbs vs spica, non-stock modifications if any...).
I don't beleive you actually want to remove the tensioner but adjust it.
I am sure there are several conditions that could cause backfiring and hopefully some other bbers will pipe up and supply some addtional info or correct me if i am wrong

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I recently dug into my 2.0liter spica engine (1973) and can suggest the following steps based off of my engine (almost identical to other seventies 2liters)
If you suspect the timing chain (i am assuming your car has a chain not a belt) needs adjustment you need to check to see if the timing chain has excessive slack.
Remove the valve cover and see if the timing chain deflects no more than approximately 1/8 to 1/4 inch (3 to 6mm).
This step above is a quick and simple check. If there is significant deflection you need to proceed with caution and follow the steps for both timing chain tension adjustment AND camshaft timing alignment.
Cams not being timed properly can cause backfiring or worse as i'm sure you know. A loose timing chain can cause the cams to be out of alignment.
You should be able to find on the board here steps for both timing chain and camshaft adjustment.
Just word of caution: if the chain needs adjustment, make sure the camshafts are close to proper alignment before making adjustments to the timing chain tension. Cams way out of alignment can easily cause major engine damage.
Tightening the chain is fairly simple but you MUST make sure your camshafts are aligned properly before attempting to start the car.
Tighten the chain first, Time the cams second.
Tightening the chain on my engine was fairly straight forward.
Remove valve cover, loosen but do NOT remove timing chain tensioner BOLT on front of engine block (?14mm?). With transmission in fourth gear, rock car foward and back until chain picks up tension. Tighten bolt (don't over due it). I don't have a torque setting but tight, not outrageous or anything as you can damage the tensioner. My timing chain tensioner took a little while to 'pop' out but once it loosened up it was easy to notice how well it would take up the slack in the chain.
Once the timing chain tension is correct with bolt retightened you should rocked the car back and forth a bit, while in 4th gear, to double check and make sure it really is tight.
You then need to check your camshaft timing.
(again, there are definitely full and detailed descriptions on the board for how to do this)
With the number one piston at top dead center, (both valves should be closed and number four cylinder valves open, a dial indicator is VERY helpful for this), timing mark on crank pointing to P, and distributor rotor pointing to the Number One spark plug
both camshafts, intake and exhaust, cam lobes for the number one cylinder should be pointing out (away from the center of the engine) and the timing mark on both camshafts should line up with marks on caps.
Adjusting the cams is not terribly difficult but you definitely want to read up on it before attempting and the camshaft tool is definitely worth the 15 bucks or so it costs (iap, centerline...).
Again, Make sure your cams are properly aligned before attempting to start the engine.
Hope this helps.