AJP V8 Timing Chain Tensioner

[Adambul]

Evening all! I'm after a bit of advise, I've just been checking and adjusting my valve clearances while trying to trace a bit of a tap and clatter at idle and I noticed that my timing chain tensioner is fully screwed in. With the tensioner fully screwed in I can still lift the chain off the tensioner by hand with ease, its slack!!! (This may explain my slight tap!!).
The engine build manual states you should tension the chain using the adjuster until you can just lift it off the tensioner pin using a 12" screwdriver. I don't really understand that statement but I'm sure it means it should be a dam site tighter than mine. I've researched this on PH and apparently you can pack the tensioner pin from within the adjustable bolt to take up the slack, which looks dead straight forward. My question is just how tight should the chain be?
Does it mean inserting a screwdriver between the tensioner pin and the tensioner and being able to just lift the chain off the tensioner pin by twisting the screw driver? i.e quite tight?

Thanks in advance

[ukkid35]

Adambul said:

The engine build manual states you should tension the chain using the adjuster until you can just lift it off the tensioner pin using a 12" screwdriver.

I've never seen that, do you have a page number?

Never seen it in the Service Manual for the shims either, should be there too surely?

[Adambul]

The service manual doesn't mention it at all! I found it after a lot of searching its on page 11 of 16 in 4-main-engine-assembly-3 of the pdf engine build manual, last item with a photo of the timing chain viewed through the engine oil fill point entry in to the timing cover.

[ukkid35]

Pure guesswork on my part but I suspect the only way you could have significant slack in the chain would be either a damaged nylon chain guide, or a missing chain guide bolt. Either way that's going to be timing cover off. I wouldn't want to run one of these with any slop in the timing chain, that doesn't seem like a good idea - sorry.

[ukkid35]

Actually I've changed my mind, the guides don't take up any tension at all, so that can only leave the chain itself (unlikely), or the material on the tensioner.

[Adambul]

Is it possible that someone has over-tightened it in the past and it has worn the guides, does it not touch them and therefore wear them?

[ukkid35]

The guides don't exert constant pressure on the chain, they merely keep it from rattling (or not in your case).

However the pressure material on the tensioner could certainly wear, but I would imagine that it should last at least 100k.

Here's a pic from Tanguero, the orange guides are perfectly in line with the chain

[greenracing]

During normal use and over time the chain will stretch slightly. Problem is there isn't a spec to define acceptable movement or length between links.

In terms of tension, the pin itself just locates in the screw in adjuster, you can pull this out and make a shim using the shoulder of a cap head high tensile bolt.

[greenracing]

I would also recommend checking the cam timing on both banks after you get the tension correct

[Adambul]

Thanks for the responses. Sounds like a combination of stretched chain and wear on the tensioner then. I take it changing the chain is an engine out job due to the clearance on the front pulley? My thoughts are just to remove the slack from the chain and not put to much tension back in to the that side of the chain and then, as said, re-check the timing.

[ukkid35]

Perhaps someone could explain to me why TVR Parts have a Simplex chain on sale, as well as a Duplex. Why would anyone think that was a good idea?

http://tvr-parts.com/tvr-parts/part-details/tvr-rg...

"Simplex Timing chain for AJP V8. This is a simplex replacement chain for the standard duplex arrangement found on AJP V8 engines. Significantly lighter, this chain is the ideal solution to all TVR timing chain requirements."

[Adambul]

They must be very confident with the strength of the chain. We hear of Duplex chains snapping so I don't think the risk would out-way the benefits of a lighter chain, if the lighter bit is actually the only advantage!

[Jhonno]

ukkid35 said:

Perhaps someone could explain to me why TVR Parts have a Simplex chain on sale, as well as a Duplex. Why would anyone think that was a good idea?

http://tvr-parts.com/tvr-parts/part-details/tvr-rg...

"Simplex Timing chain for AJP V8. This is a simplex replacement chain for the standard duplex arrangement found on AJP V8 engines. Significantly lighter, this chain is the ideal solution to all TVR timing chain requirements."

I just spotted this.. I wonder if anyone has done it? Less weight/drag.. Reliability would be a thought though..

[ukkid35]

And I guess it would be more likely to stretch as well.