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News: BetaMeeta20 12th September 2020
http://www.betaboyz.myzen.co.uk/forum/index.php?topic=4080.0
 
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Author Topic: Cam rattle ?  (Read 1044 times)
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capriblu
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« on: October 13, 2019, 12:26:12 PM »

Over the past 18 months have started to notice an increasingly prominent tapping/rattle noise from the top of my engine at the cam belt end.  Noise is intermittent only starts when the engine is fully warm and only occurs at idle. The noise disappears as soon as revs are over 1500 and when engine is under any sort of load, i.e. car being driven.   Using a stethoscope I have isolated location of noise to area around the exhaust cam wheel, definitely not valve related.  My thoughts are camshaft end float?   

Haynes manual is next to useless in providing any real detail regarding how cams are supported/located, bearings etc ...?

Any thoughts, pointers, ideas before I investigate further?
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!980 2.0 Coupe - Owned since 1990
Neil-yaj396
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1979 1300 Coupe


« Reply #1 on: October 14, 2019, 07:32:41 AM »

Cam bearing (shell?) nearest the cam wheel? I'm not sure I'd fully rule out that one of the valve buckets doesn't need re-shimming though? Noise can transfer through metal.
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capriblu
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« Reply #2 on: October 14, 2019, 09:58:53 AM »

Thanks Neil - I'm 99% certain not valve related.  Its quite a revelation to discover how much you can pick up with a simple £5 mechanics stethoscope; you can literally point the touch probe at the relevant point on the head/cam boxes and listen to each individual valve.  The noise is not typical of excessive valve clearance, is intermittent and definitely seeming to come from the exhaust cam wheel area.  Just want to get some idea of how cam is located / supported / bearings etc .....
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!980 2.0 Coupe - Owned since 1990
rossocorsa
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« Reply #3 on: October 14, 2019, 09:50:21 PM »

Take the cover off and have a look! There are no separate camshaft bearings the housing is simply accurately machined through and the alloy relies on the oil feed to keep everything healthy. I wouldn't be at all surprised if this is a tappet shim issue,  it doesn't take long to take the cover off so I'd be doing that to see if anything looks suspicious.
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rossocorsa
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« Reply #4 on: October 14, 2019, 10:02:26 PM »

Have a look at the linked video, this is me trying out the oil feed by spinning the aux drive, note you can only do this if you've done the lobe removal mod, this is not relevant to you directly but you can see the cam layout from the video.

https://photos.app.goo.gl/WKKKFfkoDZFkWt2w6
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capriblu
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« Reply #5 on: October 15, 2019, 08:08:45 AM »

Have a look at the linked video, this is me trying out the oil feed by spinning the aux drive, note you can only do this if you've done the lobe removal mod, this is not relevant to you directly but you can see the cam layout from the video.

https://photos.app.goo.gl/WKKKFfkoDZFkWt2w6

Many thanks for this - I'll have a look later.
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!980 2.0 Coupe - Owned since 1990
wheelies
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« Reply #6 on: October 15, 2019, 07:27:13 PM »

Check the cam lobe hasnít worn. They only have a think case hardening and once through the skin they wear quite rapidly
Although you would notice the engine running lumpy.
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