216 / 235 & 261 all use these exact same instructions . This is a simple DIY job that'll wake up that old , worn out clattering & smoking engine in your Vintage rig . To begin you'll need some basic tools , spark plug wrench , open end and box end wrenches , various screw drivers and a test light , feeler gauges for the spark plugs , most Auto parts Stores sell spark plug gauges for $5 , be sure to get one with .040" size stamped on it , the Counterman should be able to show you how to use it on a new spark plug , they're never , EVER pre - gapped like they'll tell you they are . Additional tools to make this job easier and turn out better are a Tach/Dwell meter and a Dynamic Timing Light , these are available in Thrift Stores and Pawn Shops very affordably , do not pay more than $5 for a used one unless you personally test it first . To begin , the cylinders are numbered 1 ~ 6 from front to back so always remove the # 1 spark plug wire from both the cap and the plug so later on you'll have a reference point , GM L6 engines have the firing order the wires connect in : 1 , 5 , 3 , 6 , 2 , 4 this is easy to remember if you think about Women : 15 is TOO YOUNG 36 is TOO OLD and 24 is JUST RIGHT . Remove the spark plugs and line them up in a row in the same order you removed them , if any have heavy , black & greasy encrusted deposits you should know which cylinder they came from . Hold one spark plug up so you can look side ways across the working part , the center thing is the electrode and it's critical this is flat across it's top with sharply defined shoulders ~ if the shoulders (edges) of the center electrode are rounded at all , the engine will not run well . Spark plugs are cheap , just buy the standard copper cored ones , never platinum or multi electrode ones , they don't work like the picture on the box that shows big , multiple sparks . Holding the plug inverted , slide the .040" feeler gauge between the center and curved over electrodes , what you want is the electrodes to *just* touch but no drag , using a wire typ gauge is best here , you want it as close to .040" as possible and in no case any less than .036" no matter what the old books say . To close the gap just tap the plug on a hard surface , the cement driveway etc. , it'll bend a little bit with each tap so go gently . To open it use either the adjuster on the wire typ plug gap tool or the smallest flat blade screwdriver you can find . You can use a tiny screw driver to carefully scrape the side electrodes clean but do not scrape the center electrode as it's easy to crack or break the ceramic insulator part . All clean and gapped (adjusted) now ? good , set them aside and remove the distributor cap , most have metal spring clips on each side , use a short flat bladed screw driver up neat the top of each spring to pop them loose , don't allow the cap to slide off center until both clips are loose . Looking in , you should see the plastic rotor piece , it may have some burning marks on the outer metal tip , this is O.K. . Depending on the year , either it will have a bent up metal blade in the center or , it'll be flat in the center of the rotor and the Dist. cap will have a spring loaded carbon brush , never both . Grab the fan pulley and rotate the engine , it'll turn fairly easily because the spark plugs are out ~ the points have a little plastic rubbing block that rubs on the dist's center shaft , this has 6 high points called " lobes " and what you want it to stop turning the engine as the rubbing block is on the highest point of one lobe , this holds the points wide open for adjusting ~ find the .016" feeler gauge and wipe it clean with a clean & dry cloth or towel , then see how loosely it fits between the open points ~ there's one screw you can loosen to allow the points to move and be adjusted by placing a screwdriver tip between the points and the distributor's plate , take a moment to find this and gently twist the screwdriver to open or close up the points until the .016" feeler blade just barely slides in between them , then snug up the screw and test the gap again as it occasionally moves as you tighten the screw . All set ? . Take the dist. cap in your hand ad place it back on the dist. , twist it until the clips line up and you feel the cap click into place on the dist , make a note of where the empty , # 1 plug wire connection is on the cap and rotate the engine until the rotor is pointing at that position then place the cap and snap the clips back on to hold it . Now , look above and behind the starter at the engine and you'll see a small hole about 1" diameter , inside that is the flywheel and hopefully you'll be able to see a ball bearing (like a BB) that's pressed into a hole in the flywheel , there's also a sharp pointer in the upper edge of the hole , it points down . this is the timing marks so you must wipe them clean with rags until you can clearly see both the pointer and the ball bearing , I like to make a circle around the ball bearing with chalk or white crayon , SWMBO's white finger nail polish etc. . Now connect your test light to the wire leading between the dist. and the ignition coil then connect the other end to the engine somewhere it'll get a good ground , turn the key on and observe if the light lights up ~ . What you want to do is this : turn the engine backwards (counter clockwise) until the BB disappears then s-l-o-w-l-y rotate it clockwise , watching both the test light and the pointer in the hole , you want the light to come on just as the BB lines up with the pointer but it rarely does so if they line up but no light , stop it there and loosen the pinch clamp at the bottom of the Dist. where it connects to the engine , just loosen it a tad , the original screw takes a 1/4" flat blade , once it's loosened up you can grasp the dist. and twist it slowly until the light *just* comes on then snug up the screw again and test the timing my rotating the engine again . I know this takes time and effort but *you* can do this , just be patient . Once it's timed , replace the gapped spark plugs and re connect the plug wires going 'round beginning with # 5 , then 3 , then 6 , 2 , 4 and you're done ~ go try to start it , it should roar right into life and idle well . If nothing else , remove and re gap the old spark plugs to .040" , you'll be amazed at how much better it'll run . If you have the most excellent Pertronix " Ignitor " breakerless ignition in your original distributor , open the spark plugs gaps up to .045"