Help Anybody know how to manipulate the chain and chain tensioner on a V12 HE

I am ready to plop the A Bank (right side) head onto the block but before I do that I have to hand crank the engine and timing chain around so that it lines up, TDC and #1 firing. I don’t know what I should be doing with the chain tensioner. So far I haven’t done anything but looking at the chain, both sides of the chain coming out of the block looks like the outside of the chain is wedged up against the walls of the block on both outer edges of the chain. Like the sprocket has dropped lower into the block but the sprocket is resting and cir clipped onto the holder.

Can you post a picture? And is the tensioner “activated” or is it retracted?

Tensioner is activated, never touched it. A mechanic at a Jag shop scared me away from doing anything to the tensioner saying they were easy to break.

Can’t take any pictures until this weekend. Got everything packed away while I work during the week.


Ok no worries about the picture, I am sure Kirbert or one of the other veteran v12 guys will chime in soon. All I can offer you is the section in Kirberts book about timing chains and tensioners. Page 64 and on talk about engine work like what you are doing.

Book Link:

Thanks William. I’m reading about it now.


Here’s what l would do in similar situation. Assuming the other head is in place and sprocket bolted up l would drop head on with cam set to close as you can to same relative position as already fitted cam by noting the timing slot position. Then rotate engine until cam timing tool fits B cam, then adjust A cam to tool as well without any further crankshaft rotation.
It may seem a bit of stuffing about but it sure beats risking sprocket slipping off support or the risk to tensioner by straightening that.

Hope this helps

No worries, if you do end up having to fiddle with the tensioner look at Bernards link. And in the unfortunate event that it shatters like they apparently usually do, then here is a link to the lowest priced tensioner which I believe is made by the exact same manufacturer as the more expensive ones which is Cross Morse Made In England.!/English(US)/parts/7e714da2-3dd8-4f4f-abcd-385ae5d88237

You should also look up a local supplier of hard liquor. You’re gonna need it when you realize what it takes to replace a broken tensioner.

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Yea, but probably no harder than any modern car chain and tensioner job. Which is not easy but doable in the car. at least it’s not like my 2017 Chevy Colorado 3.6 v6, it has like 5 different tensioners and 4 cam vvti. I hope to god that I never have do that on my truck, even though the 3.6’s are known to have timing chain issues :crossed_fingers:

On the few times I’ve found my self having to get into this part of the engine, I have found that there isn’t actually any need to manipulate the tensioner unless you need to change the cam timing.

If you haven’t turned the engine over an uneven amount when dismantling stuff and the sprockets are still enveloped by the chain, then there is only one way they can go back on if you put the camshaft back on roughly in the same orientation as it came off - i.e. the four camshaft bolts dictate that the relationship is fixed.

As for the tensioner, with the A bank cam cover off and everything else back on, you can just pull the A sprocket up and gently help the tensioner retension by pushing something long and thin against the chain/tensioner to help the chain be pulled that last bit to get the sprocket onto the camshaft. The fully retracted tensioner simply makes that job easier, but it isn’t ever essential to need to have a fully retracted tensioner to get it all mated up.

The only gotcha is that those of you who still use a distributor have to make sure the jackshaft sprocket hasn’t moved round on the chain relative to where it was before disassembly as that screws up where the distributor is pointing.

If the problem here was simply that the sprocket fell down a bit and got wedged somewhere lower down, without losing contact with the chain and therefore still remained indexed to the chain, then just yank it back out and all should be good.

kind regards

You need to be rocking the latch on the tensioner when you do this.

pic of tensioner sprockets in place held by small removeble metal plates(homemade).
works good been 25yrs!

i locked the tensioner in place before front plate, pretty simple once uunderstood!

couple pix!

. .

pic of plug for the hole in front plate!

$3. dollars at plumbing store , Lowes, home depot,etc.

Ah, wise words, about a number of automotive…challenges.


You guys are getting scary-er by the day. Sounds to me like I’m gonna need a 5th or more even before I start.

Don’t worry you got this!

Hi William,

I think I do too but waiting for the weekend to arrive so that I can start the attempt gives all the negative and positive viewpoints ample time to dwell in the realm of unknown and yet possible consequences. Lotta angst.

Another attempt to send you a private email. Please respond back to me at


Hi MerekH,

I have some specific, further in depth questions I would like clarification on. I have been trying to you a private email. Could you send me a private email at my address?

Thanks, Paul