Lotus Elan

reinstalling timing chain

PostPost by: richard » Tue Sep 07, 2021 1:38 am

What's the trick? Once I place the timing chain over the sprockets and hand turn the engine at the crank, nothing moves.

Without the chain over the sprockets the engine turns over easily. The cams turn as they should without the chain, however, when I put the chain over the sprockets it locks up. Not the valves hitting the piston tops.

I think there is a kink in the chain when I install it, so what is the trick?

I used a bore scope to look down, however I can't get a clear view. Also, the idler pulley in is the way of looking down to see how the chain wraps around the sprocket on the crank.

Any thoughts?

R. Getz
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PostPost by: Billmack » Tue Sep 07, 2021 2:40 am

Does lower camshaft/auxiliary shaft turn? Problem should be pretty evident. If the chain was kinked you would not be able to assemble to the sprockets because it would be short. You are sure valves are not hitting anything ir even each other??
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PostPost by: rgh0 » Tue Sep 07, 2021 9:25 am

Hi Richard
You appear to have turned both the cams and crank separately with the head on the block. This can result in the pistons hitting the valves and valves hitting each other. It is very easy to bend the inlet valves especially.

Once the chain is assembled with the crank and cams in the correct TDC location and tensioned correctly it should turn over OK by hand. The torque required is high as turning all 4 shafts and working against the valve springs but it is doable with a normal wrench on the crack pulley bolt. The chain cannot be fitted without it being correctly engage on all 4 sprockets.

What is the history of the dismantle and rebuild before this point as it may assist in remote troubleshooting. Photos also help showing how the problem looks

cheers
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PostPost by: billwill » Tue Sep 07, 2021 12:41 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: richard » Wed Sep 08, 2021 2:00 pm

When I turn the cams and crank independently of each other, I am only turning it a couple of degrees. When I said the main crank turns (very) easily, it is without the cam caps tightened down so the valves are not lifting.

When I put the wrench to the main crank, I see the chain 'try to move', but not the cams. I'm going to check the valves again, but the #1 cams are facing away from each other, and the marks on the cam sprockets are facing each other. The main timing marks on the crank are at TDC. Also, to check that the jackshaft is turning I take the chain off the cam sprockets and lower it so the main crank shaft sprocket is not turning, then the jackshaft/distributor rotates freely.

I noticed from other posts that I am not the only one having trouble with this. Someone said they needed four hands.

I'd like a response form those that have actually done it. We can all have thoughts on this from the comfort of our chair.
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PostPost by: Craven » Wed Sep 08, 2021 4:18 pm

From the comfort of my armchair, I don’t recall being able to fit the chain over sprockets when fitted to the cams, do you have the correct length chain. Have fitted many chains in my time.
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PostPost by: billwill » Wed Sep 08, 2021 4:37 pm

I'd like a response form those that have actually done it. We can all have thoughts on this from the comfort of our chair.


I have told you exactly how to do it in that link above including photos. Not much point in us replying if you don't really read the responses.

I have fitted the timing chain many times!!!
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PostPost by: andyelan » Wed Sep 08, 2021 6:16 pm

Sounds to me like you might have got the chain wedged in the timing case, possibly because it's got between the jackshaft sprocket and the case. Try dropping it off the crank sprocket to check it's free.
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PostPost by: englishmaninwales » Wed Sep 08, 2021 7:22 pm

After-market new timing case? I had a similar problem, discovered on trial assembly, with a Burton new backplate/front cover/removable coolant pump. The casting core for the front cover had been slightly offset resulting in the timing chain, when correctly installed, fouled the front cover casting and jamming the chain.
Malcolm
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PostPost by: AussieJohn » Thu Sep 09, 2021 5:39 pm

Have you got the spacer on the jackshaft?
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PostPost by: billwill » Fri Sep 10, 2021 12:19 am

NOTE: the chain tensioner should be fully relaxed (outwards) when checking to see if the chain is engaging properly on the mainshaft sprocket.

Having pulled it up and checked that it is correctly on the mainshaft sprocket, keep the chain hand-taut until you have got the sprockets onto the camshafts and the exhaust side is tight. only then can you relax the tension on the chain and can screw the tensioner inwards. If necessary get a friend to hold the chain up and taut or, like I do sometimes, use a rubber storage strap to hold the chain up by fastening the other end of the strap to the roof of your garage/workshop or use some similar arrangement.

With the tensioner fully screwed out it is easy to see/feel that the chain is engaging properly on the mainshaft.

I suspect you are trying to do it without slackening off the tensioner.
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PostPost by: Billmack » Fri Sep 10, 2021 7:18 pm

Kinda has to be wrong parts or poor craftsmanship
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PostPost by: Slowtus » Fri Sep 10, 2021 10:21 pm

andyelan wrote:Sounds to me like you might have got the chain wedged in the timing case, possibly because it's got between the jackshaft sprocket and the case. Try dropping it off the crank sprocket to check it's free.



Been there done that!

5 second fix. :D
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PostPost by: JJDraper » Tue Sep 14, 2021 3:24 pm

billwill wrote:NOTE: the chain tensioner should be fully relaxed (outwards) when checking to see if the chain is engaging properly on the mainshaft sprocket.


I've done the camchain thing a few times now, and Bill is correct. I would add that if you can get the chain on the sprockets, if not fully timed properly, press down hard on (heel of your hand and a good push) the chain between the sprockets to introduce as much slack as possible. This makes moving a sprocket a notch or two much easier.

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