Choosing main crankshaft bearings

[bakeLit]

Hello XS world,

I've recently opened up an engine that had metal shavings in oil, so I thought the crankshaft journals were shot, which proved to be right, what a mess it was inside.

Anyway, I am now in the process of replacing the crankshaft with a different one together with responding shell bearings. The thing is I find the chapter about identifying the correct bearings in the manual quite confusing.

So the basic idea is that I take the numbers located on the upper crankcase and the numbers on the crankshaft itself.

From left to right, this is what I get:
CRANKCASE: 3 4 4 (I've already switched the order from 4 4 3 because the upper case needs to be flipped over so that the numbers correspond to the correct journals.)
CRANKSHAFT: 2 1 1

Now the manual goes on to say that CRANKCASE NUMBER minus CRANKSHAFT NUMBER equals BEARING COLOUR, but then there's this chart - and that's when things get confusing.

Since when does 3 - 1 equal 1? Yes, 4 - 2 does equal. But... am I misunderstanding something here? Misreading the meaning of the chart, perhaps?

According to my readings, the bearings inserts should be as following:

FROM LEFT TO RIGHT:
3 - 2 = 1 (Blue)
4 - 1 = 3 (Brown)
4 - 1 = 3 (Brown)

What I found in the engine, however, was Black, Brown, Brown, so instead of the (supposedly) Blue bearing, there's a black one. Could this have been the cause of the failure?

Other question - I do have a spare healthy engine that I'm willing to sacrifice for this one (I'm thinking of just putting the healthy crankshaft with bearings into the old one that broke down) but I suppose the numbers would have to lead to successful calculations for me to be able to do this swap?

Thank you very much!

 

[NewHavenMike]

I think I would put that engine aside and use the spare. Rebuilds and machine work is not cheap and parts are only getting harder to find. Good news is you can salvage most of the engine except the crank.

 

[bakeLit]

Well, the thing is the other engine (the one that failed) is already painted and finished in other ways, that's why I'm looking for this option.

 

[dgoodsy]

The rows in that chart don't necessarily correspond with each other from column to column. What I mean is that there is no tie between crankcase no.3, crank journal no.1 and Journal bearing no.1. It is just a coincidence that Crankcase no.4, Crank journal no.2 and Journal bearing no.2 are all in the 2nd column. Just do as the instructions say, subtract your crank journal no. from crankcase no. and use the journal bearing that corresponds with that number. If they all come from different rows then so be it, example: crankcase no.5 and crank Journal no.1 would require Journal bearing no. 4.

It is clearer in my head that in my attempt at an explanation...

 

[bakeLit]

Okay, thank you, that's what I thought, but the chart sure is confusing. Further on: the higher the number of the bearing, the bigger the clearance they have? If so, would I be able to put black instead of blue if gives the whole thing enough clearance? Or is it a no-no? We all know these bearings are nearly unobtainable by now...

 

[dgoodsy]

I believe that is how it works with the bearing numbers, yes.
I really don't feel too qualified to be giving advice on bearing sizes. If the bearings were easily available and not too expensive then I would say just get what the literature tells you to. However since they are apparently tough to get I am inclined to say if there are no apparent adverse effects from using the "wrong" size bearing already then it can't hurt anything too bad.

As a side note I seem to recall someone else recently found the "wrong" size bearing in their engine as well, I think it also had to do with blue vs black bearings. hmmm...

 

[NewHavenMike]

You're thinking of having the crank machined?

 

[Jeff0133]

Took the crankshaft and bearings from an engine to swap into another engine recently with no adverse effects to date.

 

[IanW]

Is it possible to send photos of the numbers on the crank, engine case and connecting rods? I found that there was difficulty interpreting the numbers in some cases when wear made them hard to read, and seeing your exact circumstance might help.

 

[xschris]

If you have a case number of 4 and a crank number of 2 then you need a 2 ( black) bearing. Using the wrong ones will destroy the crank. They are sized at the factory for the exact amount of space. If the crank is shot then you must use another crank and match the case numbers for the new crank for the correct bearings. In your case you need a 1-3-3 , blue, brown, brown. But because the wrong bearing was in the first one the crank was damaged and now you need to replace it.