Tensioner questions with borescope video, re my other post

Thought i would make another post , while still dealing with my compression issue post .
not familiar with the tensioners full operation should there be any spring flex tension , in other wards can the tensioner retract slightly as it progressively keeps tension?
I was using my borescope and was able to view a few different angles or the chain and tensioner. from both the access hole to tensioner as well as down the filler on the B bank.
if i do move the crank a few degress both fwd and back i can see the tensioner compress slightly) when going back a few degrees . also there is a pin at the bottom that looks like it is coming out?? see pic i attached and videos are uploading and ill post a link .

other videos:

Seems i remember reading you should NOT turn the v12 engine backwards. You might want to avoid doing it again. IIRC it might cause your tensioner/ damper to crack.

Thank you Jim yes i have read that that is so. However i am just rotating or moving it backward and forth perhaps about 5 degrees and all plugs are removed. So hopefully not much load on it like trying to rotate backwards thru a cam lobe or compression :crossed_fingers:t2:

Here is a post that gives you an indication of how worn your chain is. Basically, look at how high up the square box that is the latching mechanism is.

Turning the crank backwards a bit is of no consequence, so long as you always turn it back the right way and tension in up again. From a cam/crank point of view, a slack chain tensioner will mean that the cam and crank will go slightly out of sync to each other, but since you are not running the engine, you aren’t going to do any valve damage delicately turning the engine by hand a few degrees and you’ll reestablish the cam/crank relationship as soon as you turn the engine the right way again. From a tensioner point of view, you want the tensioner to always be pushing the slack chain to the middle of the block rather than being loose where it can snag on something - that’s your concern.

The worn chain in the picture cuts into a couple of the bolts into the engine block - there is metal to metal contact.

The straighter the tensioner is, the more tension it is applying to the chain.

A tensioner that doesn’t tension is just going to whip about and will cut grooves into the plastic tensioner and chain guides in normal operation. If it is maintains proper tension, then I can’t see why the engine can’t go backwards slowly by hand - there’d be nothing for chain to snag on and the cams and crank will still be sync’d to each other.

That also means that a worn chain will allow you to pull back and manipulate an unlatched tensioner quite easily as it isn’t under much tension if the chain sits a long way into the centre line of the block. By contrast, a new chain will keep the tensioner sitting to the right hand side of the car and under heavy tension by default so there is little or no scope to allow for lateral movement.

The tensioner sits on a pin coming out of the block which you have identified - it can’t go anywhere and you also can’t change it without removing the timing cover.

You do sound as though you are describing a reasonably worn chain, so check how high up the latching mechanism sits.

kind regards

1 Like

Thank you Marek for your always insightful and informative posts .
So here are some photos of the tensioner. No I don’t have a way to actually measure easily but by the looks of it in comparison to your photographs of your warm timing chain and your new timing chain it doesn’t appear that this chain has a lot of wear definitely not new but even by the looks of the inside of the engine etc. this looks like it has been done at some point and I would say between where the tensioner lock is and the portion where the chain ride is 1 inch to an inch and a half away from one another. I guess still my question is on the locking mechanism is it strictly a one-way device in other words should it allow no movement of that locking mechanism and the rod in the reverse motion or can it move slightly backward like my one video. And the spring applies pressure ? And was able to get my borescope to look at the chain in relation to the bolts where they could wear when chain is stretched. It appears to be clear of the bolt by i would judge 3/4 inch … So Right now my ultimate question is is the tensioners holding firmly or is the lock not holding properly?

According to this my interpretation is itshould not ease tension without unlocking

However on closer examination and recording it i think this small movement may be normal based on the lower spring pin offset , and why both the rod and locking mechanism move together w/o slippage between rod and lock “Clamp/cam”