View topic - Four cylinder engine starter-generator timing chain noise

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PostPosted: Sun Oct 24, 2021 12:13 pm 
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My 1923 DB Roadster has the non-fast four engine which runs as near perfect as a 94 year old engine could be expected to run. I experienced a lot of noise and vibration from a out of balance flywheel and really noisy clutch discs, but that has been remedied with a different flywheel and clutch. However, now the engine is quiet enough to hear what appears to be a really loud grinding sound coming from the front of the engine. The starter-generator drive chain is commonly called a “silent” chain, and references gives specific details regarding its proper tension and alignment adjustments. These instructions have been followed to a “T”, and it’s still way too noisy. The question here is “What is a acceptable level of noise, may it be a “singing” chain or a “humming” chain”? I would appreciate any input from anyone who can suggest what may be done to quieten my chain……or is it normally a louder “silent” than silent “silent”?


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PostPosted: Sun Oct 24, 2021 6:20 pm 
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Have you taken the tension off the chain and inspected it? They do wear out, gets sloppy. They will make noise if too tight or too loose.


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PostPosted: Sun Oct 24, 2021 10:19 pm 
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I have taken the cover off to her three times and check the tension to make sure I had the 1 inch play the book states. I have not checked the alignment of the starter generator with the drive gear since I completed assembly of the engine. I’m thinking that’s probably the next job I had lined up for the engine. The engine, itself, Is an enigma because I got a whole box of partially assembled starter generator drive chains with the car. Likewise, I got a new appearing fly wheel and a clutch that looks completely rebuilt with the car. I had to swap out both of them because the clutch discs were badly out of balance and nearly shook the car apart, and the fly wheel was so out of balance it sounded like the rear main was about to fail. So I don’t know about the chain that’s on the engine. It appears to have been replaced when the engine was rebuilt, but if you’ve read my previous post, you’ll see the engine was assembled with a badly bent intake valve and two teeth out on the camshaft timing. I was hoping that someone who had a four-cylinder engine with the starter generator drive chain could tell me if it is indeed a silent chain, or some amount of noise was to be expected. If a certain level of noise is to be expected, I can live with that. But, if something is wrong, and the noise level is excessive, I need to fix it a ASAP.


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PostPosted: Sun Oct 24, 2021 11:16 pm 
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It is a silent chain. I can't hear yours to tell what the noise sounds like. As I said it will make noise either too tight or too loose. If the links are wore out the one inch measurement may not mean much. With it off the engine are the links sloppy? Have you watched it with the cover off to see if it dances around or binds?


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PostPosted: Sun Oct 24, 2021 11:48 pm 
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I’ll take the cover off again tomorrow and see if the forum will let me post a short video of the chain and the sound it’s making. This is a particularly vexing problem because it seems so simple to, but is a worry about damaging the engine which makes longer drives in the car impossible. The oil pressure is around 40 pounds at a high idle, and the engine idles quietly and runs smoothly at higher speeds, so I don’t think it has anything to do with the gears, crank or cam bearings.
I’ll try to be back tomorrow with a video…….thanks for your replies.


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PostPosted: Mon Oct 25, 2021 9:03 pm 
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40? I have never heard of a four cylinder DB that had that much pressure. 4 is plenty.


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PostPosted: Wed Nov 03, 2021 10:56 pm 
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Location: Portland Oregon
That should be 1/2 inch play for your year, not 1 inch.


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