Lotus Elan

Timing Chain Adjustment Tips Please

PostPost by: Robho » Fri Apr 09, 2021 5:27 pm

Hi Guys

I have tried the search facility but have not succeeded in finding help - apologies if i missed the obvious.

I have a 1971 Sprint.

The last couple of drives I've noticed on start up a 'whine' (not quite a 'thrash') from the timing chain. I'd like to check it's adjustment.

The workshop manual basically says adjust the tensioner in or out for the least noise....which seems to me a rather broad description, given the wrong adjustment could be problematic to say the least.

Should it be done with a cold or hot engine and I'd really appreciate any tips to get it right please.

Many thanks
Rob
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PostPost by: billwill » Fri Apr 09, 2021 6:21 pm

See viewtopic.php?t=26441&f=39&start=0#p175063 about half way through that long message as you are not actually doing a clay test, just refitting the cam sprockets and timing chain.
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PostPost by: billwill » Fri Apr 09, 2021 6:40 pm

I suggest that you lift off the cam cover, so that you can feel the tension in the top section of the timing chain, instead of trying to guess it by the sound.
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PostPost by: Robho » Fri Apr 09, 2021 8:11 pm

Thanks Bill

Any specifics on what tension is right?
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PostPost by: Robho » Fri Apr 09, 2021 8:24 pm

Sorry, Bill, I missed your first post with the link.

"Then the tensioner adjuster was screwed in to tighten the chain until I had just half-inch up & down movement in the chain at the top between the sprocket wheels"

Thanks
Rob
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PostPost by: alan.barker » Sat Apr 10, 2021 4:43 pm

If there is a whine it could be too tight
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PostPost by: Robho » Sun Apr 11, 2021 10:22 am

Thanks Alan

First time I've adjusted one myself so I'd appreciate a double check since (compared to my only chain adjusting experience on motorcycle drive chains!) it seems quite tight.

The manual quotes a movement of half an inch which taking into account the thickness of the chain means very approximately 1/16th of an inch upwards and downwards from the edges of the chain. This meant tightening mine.

I turned the engine over to ensure it was consistent and rechecked a couple of times for peace of mind.

Frustratingly, I still have the noise, and will start a new thread since I can describe it a little more specifically now.
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PostPost by: alan.barker » Sun Apr 11, 2021 10:54 am

Sorry but you don't need to take into account the thickness of the Chain.
It's how much it moves midway between the two Cam Sprockets.
So moves up 1/4" and down 1/4" = 1/2" movement.
Hope that helps you.
good luck
Alan
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PostPost by: rgh0 » Sun Apr 11, 2021 10:57 am

Robho wrote:Thanks Alan

First time I've adjusted one myself so I'd appreciate a double check since (compared to my only chain adjusting experience on motorcycle drive chains!) it seems quite tight.

The manual quotes a movement of half an inch which taking into account the thickness of the chain means very approximately 1/16th of an inch upwards and downwards from the edges of the chain. This meant tightening mine.

I turned the engine over to ensure it was consistent and rechecked a couple of times for peace of mind.

Frustratingly, I still have the noise, and will start a new thread since I can describe it a little more specifically now.


I have always adjusted it to be a total movement of approximately 1/2 an inch up and down of either edge of the chain, i normally set it as the actual chain width which is less than 1/2 inch. It needs a little force to test this as the jackshaft needs to move and the inlet cam needs to move to ensure the slack is moved between the cam sprockets rather than lower down
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PostPost by: webrest7 » Thu Apr 15, 2021 3:18 am

You may find this helpful.
This is the way I set tension of chain and have done so for many years

Timing Chain Deflection..jpg and


Also here is another image of timing that may be of future use to you

Timed Lotus Engine.jpg and


Have fun
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PostPost by: alanr » Thu Apr 15, 2021 4:13 am

Do a preliminary adjustment by the 1/2inch measurement method as per the workshop maunual and then use your ear for final adjustment with the engine running.
If it is too loose it will rattle because the chain is hitting the cam cover, on the other hand if the chain too tight it will whine.

Alan.
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PostPost by: Robho » Thu Apr 15, 2021 7:20 am

The photos are really clear, thanks, Dave - and exactly what I did (with the addition of rotating the engine and re-checking, a couple of times, for peace of mind).
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PostPost by: webrest7 » Thu Apr 15, 2021 7:27 am

Robho wrote:The photos are really clear, thanks, Dave - and exactly what I did (with the addition of rotating the engine and re-checking, a couple of times, for peace of mind).

Cheers Rojo,
Glad things went well..
At least you will have them there for future reference .
R Dave
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PostPost by: Craven » Thu Apr 15, 2021 11:01 am

Interesting photo’s of method, If you look at the way the workshop manual shows, illustration given, you have a chain slack of ¾” not the recommended ½”.
P1030646.JPG and
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PostPost by: ericbushby » Thu Apr 15, 2021 11:53 am

yes I agree that it could be confusing to someone coming to it first time.
But it is only a drawing and the words in the top left do say . `Total movement to be 1/2 inch`. It is a case of being obvious once you know.
It is similar in a way to where in section J (brakes) page six it shows the brake master cylinder as nearest the R/H wing, when we know that is the clutch.
Remember we learn all the time.
Eric in Burnley
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