Timing Chain Tensioners

I would drill and tap the timing chain tensioner caps and use the bolt (grade 8) and lock nut as the later caps do. That modification was made to prevent what you are experiencing with your timing chain going slack.

 

Here is a shot of one of the tensioners with the stop bolt and locking nut. I purloined this from OMG's restoration pics.
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Steve,
Be real careful to tighten the collet nut whenever you handle the tensioners. The spring is powerful enough to shoot the spring follower across the room and through a 1/4" plate glass window. Tighten collet, remove assembly from engine, place in a big vise that can hold assembly endwise, loosen and let things come apart slowly as you unwind vise handle. Add the 6mm locking screws and nuts. The lock screws and their nuts should be full out when setting tension. Lock the collet when chain is good. Run screws in to lock adjustment. Put red silicone or mild loctite on screw at tensioner body. Run locknuts down screws and tighten. Sealant will prevent oil leaks around locking screws. Sounds like you dodged the bullet. Good luck.
John

 

Copper washer is better than silicone sealant. I once tried silicone only to have it leak. Then used soft copper washers to seal the 8 mm threads with the lock nut. Worked perfect.

When tightening the newly added locking screw, you need only tighten the screw finger tight (plus a tiny bit more) before locking it with the lock nut. Do not try to tighten the new screw any tighter.

Order of assembly is important.

First reinstall the chain-tensioning mechanism with the screw completely out, or unscrewed so that it is almost out. Make sure the collet nut is LOOSE. Turn the engine to move the chain and cams. Then turn the engine in the reverse direction for a few degrees. Have someone do this (down at the crank) while you observe the cams/chain. You will notice that when turning in the opposite direction the chain will push the tensioner gear plunger all the way into the collet. This is a good thing. Then when you turn the engine again in the proper direction the plunger will snap out and take up all of the slack in the chain. This is the proper adjustment. Do not try to force the plunger/gear assembly out any farther (as with a long screw driver).

Now tighen the collet.

Place copper washer and locking nut on new backing/locking screw.

Now screw in the new backing/locking screw finger tight. Add, perhaps, a minimal additional torque with your 10mm spanner. Just a little to preload it against the plunger. All it has to do is act as a stop for the plunger to prevent it from slipping in the collet and loosening the chain. If you try to tighten it more than finger tight (+ a smidgen) you are likely to strip the threads on the collet cap. You will be turning a screw against a fixed plunger end, and there are only a few threads in the collet cap.

Tighten the locking nut on your 8 mm screw...not too tight.

Viola! Your are ready to rock and roll.

Jim S.

 

Gents, I noticed that the rear chain on my car was noisy and i was suffering an annoying oil leak which i couldnt trace. It now transpires that the 6mm bolt and locking nut has fallen out of the tensioner for the chain on No's 4,5 and 6 cylinders! I can get a new bolt in (with some difficulty) but have i caused any damage and what would be the best way to get the chain back to the correct tension from this juncture?
Thanks,GP

 

if you have not jumped timing, you have not done any damage.

Putting in a new bolt should cause the tensioner to take effect again and just tension as per the book. Loosen the bolt, tension the chain and manually turn the motor over at least one full turn, the manual part is important, I got lazy once and used the starter and jumped a link on the timing, no damage done but lesson learned.

Mike

 

Graham,

Loosen the collet, turn the engine by hand (socket) a few degrees in each direction until you hear the plunger snap back against the chain. This is the proper tension. Now tighten the collet. Now introduce the new 6mm bolt, copper washer, and lock nut. DO NOT TRY TO TIGHTEN THE 6 mm TOO TIGHT. Hand tight against the plunger is fine. Perhaps 1/16th of a turn just to snug it against the plunger. Otherwise you will surely strip the threads cut in the center of the collet nut. This 6 mm is trying to move against the stationary plunger. All the 6 mm does is act as a stop against which the plunger cannot slide out.

Jim S.