Lotus Elan

timing chain tension varying

PostPost by: checkrail » Wed Jun 17, 2020 3:47 pm

Hi I have had the head off to cure oil leaks, the only things replaced are the necessary gaskets.

The timing marks are nice and level, but the timing chain tension varies as you rotate the crank during a rotation, it had the correct amount of movement before with plenty of adjustment left.

After a rotation the tension is correct, is this anything to worry about?

Thanks for any help John
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PostPost by: Donels » Wed Jun 17, 2020 4:12 pm

Are you sure the tension is changing and you’re not just feeling the loading change as the cams load and unload?
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PostPost by: h20hamelan » Wed Jun 17, 2020 4:50 pm

+1

do you think the spring in the tensioner is okay?
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PostPost by: 2cams70 » Thu Jun 18, 2020 10:06 am

Yes agreed it's a pretty dubious unscientific method described in the workshop manual for setting chain tension. 1/2" slack measured between the two cam sprockets - WTF?? It all depends on how hard you yank on the chain as to what the measured slack is!! For reference I rotated the engine in it normal rotation direction for a bit and did a guestimate of the slack by pulling on it by what I considered a "reasonable" amount. To check again rotate the engine for a bit again to settle things and them measure again by pulling on the chain by a "reasonable amount" What other methods are people using?
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PostPost by: rgh0 » Thu Jun 18, 2020 10:46 am

You can determine the required 1/2 inch free play in the chain between the cams by applying enough pressure on the chain when measuring the 1/2 inch number to move the cams if needed against the spring and follower loads on the cam. Doing the check at a number of points as you rotate the crank over 2 complete turns gives you confidence you have it right.

Works for me

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PostPost by: Craven » Thu Jun 18, 2020 11:20 am

If the chain rattles it’s too loose, if it whines it’s too tight.
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PostPost by: checkrail » Thu Jun 18, 2020 11:53 am

Thanks guys for all your help. I've checked the tensioner device and it's fine with a good strong spring, before I pulled the head I noted the amount of thread showing on the adjuster so it should now be about the same.
Mine's a +2, I wish there was a bit more clearance between the crank pulley and the rad, fed up with skinned knuckles!

Cheers John
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PostPost by: rgh0 » Thu Jun 18, 2020 12:09 pm

checkrail wrote:Thanks guys for all your help. I've checked the tensioner device and it's fine with a good strong spring, before I pulled the head I noted the amount of thread showing on the adjuster so it should now be about the same.
Mine's a +2, I wish there was a bit more clearance between the crank pulley and the rad, fed up with skinned knuckles!

Cheers John

I sympathise with you as I have suffered the same for many years. Apparently Snap-on make a long handled ring spanner that fits on the front bolt and enables turning of the crank without skinned knuckles on the
radiator with it in the standard position for an Elan or Plus 2. I must get myself one.
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PostPost by: h20hamelan » Thu Jun 18, 2020 1:57 pm

Short 3/8 socket fits, i have a nice 20” ratcheting breaker
So i can just keep ratcheting, as 1/2 the battle is getting the thing on the bolt
Otherwise, one could weld on an extension. On a standard spanner
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PostPost by: checkrail » Sat Jun 20, 2020 1:37 pm

Up and running again, just had to tighten the timing chain.

The only thing when I refilled the rad although the car was still sloping uphill on the ramps and the heater was on hot, I forgot to squeeze the top hose. I now have an airlock with heater blowing cold.

Is the answer to drain about half the rad and try again?

Thanks for your advice, John +2
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