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Apr 18, 2012 10:11:37 GMT
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I've read in a few places that accelerating from low engine speeds causes the timing chain to stretch / belt to snap.
Why is this? I understand the engine works harder to pull the car forward but how, specifically, does that affect the timing chain / belt?
BTW, I don't labour my engines. I prefer to drop down a cog than hear my engine struggle.
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1985 Mercedes W123 230E - 5 speed manual & 2011 BMW F11 520d Touring - 8 speed automatic.  |
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Apr 18, 2012 11:24:39 GMT
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I don't think it does. I can't see why the output load on the crank would affect the cam.
I think mainly, snapped/stretched timing chain or belt is down to poor maintainance - infrequent oil changes damaging the cam bearings and increasing drag to the point where the weakest link gives out first.
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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Apr 18, 2012 11:26:46 GMT
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I don't think it does. I can't see why the output load on the crank would affect the cam. That's exactly what I think, but I've heard and read to the contrary! |
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1985 Mercedes W123 230E - 5 speed manual & 2011 BMW F11 520d Touring - 8 speed automatic. |
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Apr 18, 2012 11:46:14 GMT
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isn't there high loading on the cam and valve gear at low engine revs? and why they recommend running cams in for a period of time at speeds about 2500 rpm etc?
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ChasR
RR Helper
motivation
Posts: 10,309
Club RR Member Number: 170
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Stretched timing chain - why?ChasR
@chasr
Club Retro Rides Member 170
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Apr 18, 2012 17:58:07 GMT
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I thought also that cambelts were stressed more when idling. Oddly enough, most of the snapped cambelts I have seen have snapped at low engine revolutions.
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scruff
Part of things
Posts: 621
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At idle the engine is accelerating/decelerating rapidly as the engine revs hunt, might only be tiny but the belt tension is changing all the time. Also oil pressur eis low at idle which won't help.
When revving the load ont he belt is much more stable, higher, but stable and oil pressure is up too.
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1994 Lotus Esprit - Fragile red turbo with pop up lights.
1980 Porsche 924 - Fragile red turbo with pop up lights.
I spy a trend...
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Apr 20, 2012 13:08:09 GMT
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yer most belts snap at low rev's because there isn't enough rotating inertia so the belt take's more kick back loads and its the low speed variable load that snaps the belt, especialy when you let out the clutch.
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Last Edit: Apr 20, 2012 13:09:41 GMT by Deleted
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djefk
Part of things
Posts: 844
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Apr 20, 2012 21:24:59 GMT
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Wow - Never even thought about that!
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