timing chain tension

[donmarconso]

Hello everyone,

I was removing the cam covers to check the valve clearence and I noticed, that the RH timing chain seems somehow loose to me:

https://youtube.com/shorts/pZX6veEc0cU?feature=share

The LH timing chain seems to have more tension:

https://youtube.com/shorts/71tYTZW3_fc?feature=share

Running the engine there is no rattle noise or something. Do I need to worry about this or is it in the normal tolerance range?

Thanks in advance!

Regards, Marcus

[wilf]

Hi Marcus.

Surprised you got no replies to this, so here goes:

Yes, that chain does look a bit loose, it ought to be snug up against the guide at that point, but there again, the tensioners are operated by oil pressure, so could slack off a bit when the engine is not running. In your shoes, I would get a boresope camera down to see how far the tensioner shoes are out of their housings - that is a common way to see if chains are worn and therefore "stretched". (yes I know they don't actually stretch, but hey ho).

[MikeParker]

Hello everyone,

I was removing the cam covers to check the valve clearence and I noticed, that the RH timing chain seems somehow loose to me:

https://youtube.com/shorts/pZX6veEc0cU?feature=share

The LH timing chain seems to have more tension:

https://youtube.com/shorts/71tYTZW3_fc?feature=share

Running the engine there is no rattle noise or something. Do I need to worry about this or is it in the normal tolerance range?

Thanks in advance!

Regards, Marcus

The cam-shaft has certain positions in which it likes to sit and provides quite a lot of torque in doing so. So it can be that the chain on one side of the sprocket can be very tight and there can be play on the other. As you crank over the engine, the side will change. The amount of play should be no more than that allowed by the free movement in the tensioner. The tensioner has a ratchet, so that after moving out a millimeter or two (under oil pressure) it cannot then move back. So there can be that mount of free movement on what is a short length of chain either side of the tensioner. That will equate to a proportionately bigger lateral movement on the longer stretch of chain that you are looking at.

So what you seeing could be OK, but as wilf says, best to check the tensioners haven't come to the end of their travel. The rubber tensioner head hits a small metal bracket when fully extended.

[donmarconso]

Thanks for your feedback Wilf and Mike! (I already was suspecting that this was an inappropriate topic )

I will turn the engine and see how the chain behaves and will try to move my little USB cam down to the spanners. Curious if I can see something there. Will let you know!

[MikeParker]

Certainly not inappropriate. Timing chains skipping teeth is a well known issue and definitely to be avoided! So always worth asking about anything that seems unusual. The two major problems are the tensioners coming to the end of their travel and the teeth on the small crankshaft sprockets wearing right down. The aftermarket replacement crankshaft sprockets are made of what appears to be unhardened steel and to be avoided unless your originals are in bad shape.
Mike

[jbuckl]

I got crank sprockets measured for hardness.
compared to n.o.s. Sprockets. Report was both were 45 ish ( bottom of the lowest scale HRA. the new ones were similar)
currently there’s only pub talk and anicdotal evidence that crank sprockets are too soft.
However, I did get a pair treated to being them up to a higher hardness. (58 hrc) Expectedly, they had grown & needed to be re-sized to fit. Hardness work done by Wallwork.
The engine those are in is still running in.
Also anicdotally, sprockets that are too hard are also said to be a source of early chain wear. ( not my comment)

[mole42]

currently there’s only pub talk and anicdotal evidence that crank sprockets are too soft.

I have evidence in my garage that new crank sprockets can be too soft. I replaced both, one of which wore away the teeth within 10,000 miles. I'll look out photos later.

That one was replaced with one of the old ones that showed no wear and has behaved perfectly since. I do a lot more miles in my car thatn most Stag owners, it's my only car and I rally it too.

[wilf]

Crank sprockets are an item I view with the borescope every 500 miles or so, as I changed mine when I did the timing chains. So far so good.

[MandM]

I listed all the reports of "soft crank sprockets" listed on the forum and photos off the sprocket from a Norfolk members car and sent it to the committee and SOCTFL it took over 7 months to get a reply!

This is the e-mail that I sent in Feb 2021

Hi **** , sorry it’s taken a while to reply but things get in the way ,hope you are well and staying away from the bug.
The above photo is of a crank sprocket from one of the Norfolk members engine that was caught just in time late last year.
I also have see many comments over my membership of the SOC on the forum of poor quality Sprockets and timing gears , so it would seem that we have a problem with these.
I was told (9 yrs ago) when I changed my chain’s to use the old Renold tensioners and pads if they were not badly worn as the new ones have softer rubber, and the oil feed is located in the shaft not the pad which gives less chain etc lubrication. (This information on using the pads came from a long standing member)
I was also told to use the old Guides where possible for the same reason (I still have the guides that I purchase 9 yrs ago from Rimmers in the garage ,(Paper weight?), so I went and had a quick look on the forum for sprocket problems and stopped recording them at 16 threads with numerous posts. There will have been more members that have had trouble with these sprockets as only a small proportion of the SOC membership use the forum, I think that here in Norfolk there are 4 members who use the forum out of I think 115 members that Chris has on his members list, so on that bases we could easily double the amount of problems that have occurred with these sprockets, some will not know that they have a problem for years as they do so little mileage in there stags.
Having now covered 20,000 miles since I changed to German chains, I’m now starting to think what do I do?, where do I obtain decent quality parts?, in the next couple of years to replace my 40,000 miler sprockets, that were fitted to my engine by Abinger Hammer Motors during an engine rebuild.
Since I purchased my stag, I’ve carried out lots of work and replaced/repaired or refurbished most of the car, which is all part of the enjoyment of owning the car. I have also had to go back and repeat jobs that should have not been necessary due to poor quality parts, some parts that I have ordered have not made it on to my stag as they are of very poor quality, this part of ownership is very very frustrating and expensive.

I think that it would be a good project for SOCTFL to have look at obtaining sprockets from the various sources and check the hardness and then work with the manufacturer to improve the product, if they don’t what to work with SOCTFL. May be SOCTFL could have some made from a different supplier .
If there is not a will to carry out this project that affects us all, perhaps the SOC and SOCTFL could officially recommend a Supplier of sprockets.

I note that Peter at LD Parts does not sell the Crank sprocket (This has changed he now does)??

I’ve attached a list of threads on a word doc

Look forward to hearing from someone on this subject


Martin wells (*****)

Very frustrated SOC member





rays sprocket.jpg

This is the reply on 09-09-2021

Hi Martin.

Following your enquire about sub standard crankshaft sprockets.

I have done some investigation work by contacting the major stag engine reconditions. This represents approximately 60 engine rebuilds per year.

These specialists, reported that all the sprockets on the market come from the same source, and without exception, non of them have experienced any problems.

They were also very quick to point out that there many other reasons why sprockets would wear badly. incorrect tension, poor alignment, Tight camshaft due to heads needing excessive skimming. The list goes on.

There was a discussion about this subject at the SOCTFL meeting on 2nd September. It was decided that at the present time there was no need to take this further as our efforts would be better spent on other projects.

I hope that this explains things for you.

Kind Regards

_____________

I will still carry on recording the reported sprocket Problems for my own info



"STILL A VERY FRUSTRATED SOC MEMBER" as I have another question/report still not answered that was sent to the committee on 20/08/2021 which is on a different subject, it has been chased on many occasions!

[mole42]

Here's the picture of the one I had:

Sprocket comparison.JPG

[jbuckl]

I did my best to measure & compare available vs n.o.s. crank Sprockets hardnesses.
Original n.o.s. Crank sprockets are almost off the bottom of the H.R.A. Scale.

I also asked a very respected rebuilder if they had sprocket hardness concerns… they did not.
perhaps we could speak? I called you both about this …
both responders have my number… I understand it’s apparently not cricket to mention suppliers names here.

[jbuckl]

I did find worrying wear on a members engine crank sprockets.
I was able to :- 1 locate the cause & 2. Establish the previous rebuild firm.

call me / pm me for more information.

The badly worn sprockets were not at fault in this case, as far as could be established.

[MikeParker]

I did find worrying wear on a members engine crank sprockets.
I was able to :- 1 locate the cause & 2. Establish the previous rebuild firm.

call me / pm me for more information.

The badly worn sprockets were not at fault in this case, as far as could be established.

Julian,

So what was the cause? No need to know the company.

I had original sprockets up to 80K miles. I then changed the crankshaft sprockets with the chain and when next checked, about 40K miles later, both crank sprockets looked liked Richard's picture above. The camshaft sprockets were still fine. The chain did not seem to be worn either. A simple scratch test showed that the worn crank sprockets were much less hard than the original cam sprockets Unfortunately I threw away my perfectly good original crank sprockets so can't comment on their hardness.

I have never seen sprockets wear like those crank sprockets on the Stag, so it is definitely an issue in my book.

Mike

[fussydave]

Is it possible that the rapid wear could be down to using different chains to the original type? If non-standard chains are harder than the standard ones could this not accelerate wear on the sprocket?

[jbuckl]

Is it possible that the rapid wear could be down to using different chains to the original type? If non-standard chains are harder than the standard ones could this not accelerate wear on the sprocket?

That’s a possibility.