Lotus Elan

Timing Chain Slip

PostPost by: sk178ta » Thu Jun 02, 2005 7:38 pm

I`ve been told that over reving could result in the timing chain jumping a couple of teeth. Is this possible? and under what circumstances?
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PostPost by: gjz30075 » Thu Jun 02, 2005 7:44 pm

I suppose its possible but not really probable if you keep the free play to specs. And I suppose it could happen if you have really worn sprockets. Maybe some of the racers can chime in.

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PostPost by: elans3 » Thu Jun 02, 2005 10:30 pm

Only as Greg Z says, there's no other way, unless something breaks.
Even if the sprocket teeth are badly worn, but the chain tension is correct, I can't see it jumping at all. Something would have to break.
I've rallied these engines for years in the past, and never seen one break.
Seen one come adrift on a friend's car when he fitted one with a split link, (and installed it the wrong way round ), but never jump teeth.
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PostPost by: types26/36 » Fri Jun 03, 2005 7:44 am

I also find it hard to believe a chain would "slip" even given high revs, there would have to be something seriously wrong for this to happen and I think anyone who has blamed a "slippling chain" without first having a major fault should think again.
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PostPost by: rgh0 » Fri Jun 03, 2005 11:04 am

I have seen over 8500 rouutinely and 9000 rpm on occassion on mine with the standard chain and sprockets and never had it slip so I dont think revs alone will cause it.

Poor adjustment so its too loose or very very worn crank sprocket is the only way it can slip IMHO. The crank sprocket wears much faster than the cam sprockets due to its higher load and smaller diameter and less teeth so you need to keep an eye on them in high mileage engines. I routinely replace them with an engine rebuild as impossible to actually check without pulling the sump.

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PostPost by: GrUmPyBoDgEr » Fri Jun 03, 2005 11:41 am

I've never heard of problems with timing going out on twin-cams due the chain jumping the sprockets. The tensioner is purely mechanical which although needs to be kept in adjustment is in fact a plus point. Modern engines with chain driven valve gear and spring loaded hydraulic timing chain tensioners can be provoked to slip by rolling backwards down hill with the engine in gear. This puts all of the forces into the chain on the tensioner side, causes the tensioner to retract & results in a loose chain which could hop over the intake & exhaust cam sprockets.
Engines with (toothed) timing belts can be prone to tooth jumping if the belt is not replaced within the given period.
The 1300cc twin-cam that was in my Lotus 23B never gave problems with revs up to 10.000 RPM
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