engine main bearings

[JHZR2]

Hi,

Im curious about something. I clicked the ford 500 link on one website to see what the car was like, now that its coming out. They had engine specs, and one of them listed actually was engine main bearings. The duratec 3.0L engine had 4 main bearings.

Isnt this low?

My I5 mercedes turbordiesel had 6, I believe, and I also think that most BMW I6 gas engines have 6 main bearings. My BMW M42 I-4 1.8L engine has 5 main bearings! Is it because the overall engine is more compact in a V design, and the parts arent as long, so they dont need as many bearings? I dont know, but Id like to

dont engines with more main bearings tend to last longer? That was my impression, but I dont know a lot about it.

Thanks,

JMH

[ October 27, 2004, 11:24 AM: Message edited by: JHZR2 ]

 

[XS650]

Good inline engines have one main per cylinder plus one main. One between each crank throw and one on each end.

Good V configuration engines also have one between each crank throw and one on each end. The difference is that on a V engine,two cylinders share each crank throw. There is no room or need for more main bearings.

The number of bearings is more a matter of controling crank flex in bending than bearing loads. Inline engines have longer cranks so need more bearings.

9 cylinder radial aircraft engines have one crank throw and two main bearings. They have very short cranks.

 

[XS650]

quote:

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Originally posted by labman:
I don't know how many main bearings the old GM straight 8's had, but I believe GM gave up on them because of crank flex problems.

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They are a lot longer and heavier than a V-8 for the same displacement and power. It's systems integration issue as much as anything

Going from memory, Buick straght 8s had 5 main bearings, Packards 9. A Packard engine was a lot smoother sounding than a Buick if you reved the snot out both. I gotta think most straight 8s had less than 9 main bearings. Even most sixes and V8s had less than a full compliment of mains back in the good old daze. Ford flathead V8s had 3 mains.

Mercedes made some straight 8 racing engines in the late 1950s. They took the power off the middle of the crank so didn't have flex peoblems.

 

[labman]

I don't know how many main bearings the old GM straight 8's had, but I believe GM gave up on them because of crank flex problems.