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jdemaris
02-27-2004 19:13:53
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Re: question for jdemaris in reply to jim/pa, 02-27-2004 16:22:24
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Before I commence with a long boring post, I'll bet you two dollars you've got worn out balancing shafts and bearings. Typical for a 450 series. I have no way of knowing exactly how well you checked the rod journal (no negative implication intended), but as long as it wasn't egg-shaped too badly, and the clearnace wasn't excessive, it ought to be fine. I've put together many, some with standard, and some with .001 or .002" undersize. I've cleaned up the main and rod journals with emory cloth and they lasted a long time. That being said, besides being egged shaped, or the clearance being excessive, you have to be very careful about rods in those engines. The big end of the rod, that holds the bearing shells, will itself get out of round if it got real hammered. If that's the case, the bearing shells won't fit properly, and they won't last. When rebuilding those engines, as a matter of routine - I have the rods checked and resized if necessary. Resizing in not expensive, just takes shaving the cap a little, and then honing back round to specs. Getting back to your engine. The 450 engine is prone to low oil pressure problems after warm up once it's had a few in-frame rebuilds. That's because of the balancing shaft bearings. The camshaft bearings rarely wear. Usually, during every in-frame, rod bearings, sometimes mains, pistons and sleeves are changed, and maybe also new oil pump gears. The balancing shaft usually isn't touched because is requires a lot more work. Thus the problem. I've worked on countless 450s that had this problem; good oil pressure at start up, and then it would gradually go down until it was near zero at idle with a hot engine. That was one of the plusses for the 350s, no balancers. Deere starting making the four cylinders with the shafts left out and the oil holes plugged, but there were a lot of customer complaints about low-speed vibration. Just to be a little technical, I read some engineering data about the natural tendicies of engine configurations. It states that most naturally balanced engines are 3 cylinder and 5 cylinder, and the most vibration prone are 4s and 6s. I guess that's why Mercedes has a five-banger.
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