Quote:
Originally Posted by BRENT in 10-uh-C
Something worth mentioning in this. There is a misconception that if an insert bearing goes bad, it can be replaced with another insert. While the logic of this seems like that should be so, the issue is that most people wait until it is too late to replace the insert shell. When the thin bearing (soft metal) coating on the insert shell has been worn-away, the hard metal of the shell begins scratching the crankshaft journal pin causing that ground surface to become rough. So we can all imagine what happens next when a new insert shell is placed against a rough crankshaft pin.
Also, I have experienced several situations where the inserts were worn enough that before the driver could catch it, the bearing rotated in the main cap. When this happens, it will distort the cap. The proper way to correct this is to grind the cap and line-bore the block again. This generally means the pan rails and the main web needs to be surfaced by about 0.0005"-0.001" to make all the mains round again. Then the boring bar set-up must be changed to make sure the timing gear lash is not too tight.
So while the inserts can seem easier to do on the front side, there can be stress involved in redoing that conversion too. And for what its worth, there are plenty of quality craftsmen that can still cast bearings. The longevity is generally longer when the cast bearing is done correctly, however many hobbyists just want something done that will last them until they are done and then the next owner can "cleanup the mess" if something goes wrong.
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Brent you are completely right, I forgot to mention that. Funny as it has happened to me. Sometimes you can get lucky as the insert is softer than the crank and you can remove it with crocus cloth. But as you said, let it go too long/hot and it will score up the crank and you will need a different one or a regrind.
Debating between babbit vs inserts is like comparing apples to oranges. They are different and both have pros and cons as you know. I will say that if they are both done properly by somebody like you then they will last a long time. Seems we only here about the bad craftsmen though!