Posted: 2/22/2007 9:28:35 AM EDT
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Coworker and I were discussing vehicle engine life. In general, which engine has the longest life expectancy, a big or small engine. Pushrod or overhead cam? I'm pretty knowledgable in engines, and I am pretty sure I know the answers. But I'm looking for other opinions. |
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The types of metal the engine is made of, how precisely the engine is balanced, compression ratio, bearing surfaces, power output, etc... would all be huge factors. Everything else being equal, a pushrod I6 is probably up near the top. Inline 6 engines (V12 and H6 too) are naturally balanced, and don't need balance shafts. Pushrod design is probably the simplest and strongest. |
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It depends entirely on how the engine is maintained. Generally, my experience has shown that the large oversized engines tend to live longer because they aren't worked as hard during the course of their service. Perfect example. A 5000lb Chevy 2500 4x4 Suburban. Which engine is going to take the worst beating trying to move this 2.5ton tank around ??? A: 350 ? B: 454 ? 
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+1 I have had 2 1991 Ford Escorts with 1.9L 4-cyl, both pushed well over 300K before I sold them, a 1985 Volvo Turbo Diesel with a straight 6 that went into 300K before selling, and a 1993 Honda Accord with a 2.2L 4-cyl that died after 220K. I took very good care of my Fords and my Volvo, and treated the Honda like crap. I think the biggest factor in life expectancy is maintenance and how much work you are willing to put into it. |
Yep, high RPMs shorten engine life. That is why sometimes super/turbo-charged engines last longer because they develop their max HP as lower RPMs. The flat head engines used to last a long time because the compression was so low that it never stressed the engine. |
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Agree on the maintenance point. Given the same level of maintenance, yes, there will be differences in engine life depending on the specific type. Having said that, to date the best engine I have ever owned, overall, was the Ford 300CI I-6 in a 94 PU I had. Loaded with raw torque and never burned a drop of oil the whole 168,000 miles I owned it. (sold it - should have kept it). CMOS |
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Define "big" or "small". An ocean freighter engine will last a LONG time, as will a locomotive diesel, but not because they are big. Block content seems to have much more to do with it than configuration. Early Jeep I6 engines last an incredibly long time, even though they are "antique" pushrod engines because the early blocks had a high nickel content iron. Operating speed and number of startups are much bigger factors, to an extent that the other variable almost don't even count. |