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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
Posts: 24,705
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actually, at one time, and maybe they still do, porsche made a 911 motor for use in aircraft with timing gears, no chain, no belt. so it can be done, and it MUST be reliable.
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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08-12-2004, 08:26 AM
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Join Date: Mar 2004
Location: Winston Salem, NC
Posts: 464
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In some domestic V-8 set ups, the chain is eliminated with gearing. There are two main reasons for it- 1)it insures valve timing through eliminating any possibility of chain stretch and 2) eliminates the possibility of chain breakage because of forces generated by radical, high lift cams. As the engine rotates, the cam undergoes a series of "jolts" as the valves are actuated. If strong and frequent enough, these jolts can concievably damage a chain drive, hence the reliability for uses like aircraft.
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86 951- again on the road, but needing some more TLC 82 931- again among the rolling "If yer paint aint chipped, you aint passin nobody." |
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08-12-2004, 08:42 AM
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Join Date: Feb 2000
Location: Kingsport, TN
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Mercedes has used chains in their aluminum engines for many years. The chain on my old 1980 450 is about 6 feet long. The engines are durable and there is no problem with thermal expansion and chains. My 1980 has 150K on it. The chain was replaced at 100K. This engine is far from a performance engine.
On the other hand my 400E has 32v and 4 cams. It is also chain driven with an aluminum block and heads. It could be considered a performance engine. It's redline is about 6K. My 18v V-6 AMG supercharged MB also is aluminum with a chain drive. It is definitely a performance engine. So I would tend to say that chains can be used with aluminum blocks.
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Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
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08-12-2004, 08:52 AM
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Location: Winston Salem, NC
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I'm not saying they can't, but how are the chains tensioned and what mechanisms are there to keep that tension constant?
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86 951- again on the road, but needing some more TLC 82 931- again among the rolling "If yer paint aint chipped, you aint passin nobody." |
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08-12-2004, 09:28 AM
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Parrothead member
Join Date: Jul 2003
Location: Monmouth county, NJ USA
Posts: 13,853
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There are chain driven valve trains that use spring loaded tensioners.
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Vinny Red '86 944, 05 Ford Super Duty Dually '02 Ram 3500 Diesel 4x4 Dually, '07Jeep Wrangler '62 Mercury Meteor '90 Harley 1200 XL "Live your Life in such a way that the Westboro Baptist Church will want to picket your funeral." |
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08-12-2004, 10:07 AM
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Parrothead member
Join Date: Jul 2003
Location: Monmouth county, NJ USA
Posts: 13,853
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also the amount of tension on the chain is such that the effect of thermal expansion would be miniscule.
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Vinny Red '86 944, 05 Ford Super Duty Dually '02 Ram 3500 Diesel 4x4 Dually, '07Jeep Wrangler '62 Mercury Meteor '90 Harley 1200 XL "Live your Life in such a way that the Westboro Baptist Church will want to picket your funeral." |
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08-12-2004, 10:09 AM
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Join Date: Feb 2000
Location: Kingsport, TN
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The old one uses springs, plastic sliders, and an oil pressure piston thing. I have never worked on the 3 and 4 valve engines so I don't know how they are arranged.
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Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
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08-12-2004, 10:37 AM
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Join Date: May 2004
Location: Brandon FL
Posts: 371
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Don't forget about the need to oil the chain/gears. But this could be a good thing. Only the crank seal and timing chain cover gasket need to be replaced, when it starts leaking, instead of the 4 seals now.
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Rick 99 996C4 06 525XI 87 944S - Sold 77 924 - Sold |
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08-12-2004, 03:35 PM
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