Scoring in a crankshaft block bearing for an old Briggs 5HP

[creia]

1977 Briggs 5HP Model 130202 ("Koolbore") aluminum block
There is no (separate) "bearing" supporting the crankshaft journals on these engines, per se. The "bearing" is a milled/polished hole in the aluminum block (for the magneto side) and in a milled/polished hole in the aluminum crankcase sidecover (for the PTO side).

When inspecting this engine during disassembly I noticed that both holes showed scoring (easily enough to catch a fingernail in), yet the ID's for both were NOT worn oversize, and still in spec.
I went ahead and swapped out the sidecover for another one w/o scoring and ID in spec.- easy peasy.
Here is my question: On the magneto side, how big a deal is this scoring? Is ANY scoring justification to reject the block for a rebuild? How much scoring is too much? The crank journals show no scoring whatsoever and the OD's are within spec.

I would really like to use this block if possible as the bore and valve guides are still well within specs. I know that the block hole on the mag side can be reamed and a bushing installed, however, I do not want to go through that process and would just try to find another used/vintage block that is all within specs instead (no easy task).Sooooo......., in summary, is this scoring a deal breaker?
Thank you,
Michael

[bgsengine]

If the bore of the journal is in spec, and crank is clean, I would make sure there's no raised ridges causing metal to metal (a little 600 grit wet or dry with some WD-40 , polish it up a bit with a wood dowel sized to fit the hole with paper wrapped around it, and then re-check journal dimensions to be sure it isn't out of round either) , Then I'd just call it a feature (oil galley for extra lubrication!) and throw 'er back together.

[38racing]

Could you fill the groove with jb weld and sand back as per bsengine or as he said just an oil groove.

[bgsengine]

Could you fill the groove with jb weld and sand back as per bsengine or as he said just an oil groove.

Nope! I have seen that attempted, with disastrous results. The JB Weld does not really meld with the aluminum, and different expansions rates guarantees it will separate, then it becomes a wedge between the crank and the bearing journal...

Better off running it as-is even if you DON'T try to smooth out the scoring...

Should cut up your Mechanics card if you really believe that JB Weld would be a good idea to fill a bearing journal.

[RoyM]

[KE4AVB]

I definitely second that about tearup your mechanic's card as JB Weld is not a product I can trust to do anything here. Everytime I have tried it; it has been a major failure.

It appears there is no market for steel backed aluminum bushing either for these small engines.

If push come to shove then a bronze bushing type bearing could be machine the to fit. But that does require a pretty good machinist to make them as you would need about a .001" interference fit. Never tried on a crankcase bore however.

[creia]

Many thanks to all for the interest in my thread and replies.
No, I am not comfortable AT ALL using JB Weld in this application JB Weld is a good product (and I've used it many times over the years), but not in this case.
I'll take a closer look for any rough edges and address those as Brian has stated as/if needed.
Michael

[KE4AVB]

This is something I try to keep telling myself. That everybody's experience with JB Weld is not the same as mine. But in order for myself to trust a product it must perform as advertise when I follow the instruction provide by the manufacture. I even had one Permatek product not to perform as advertised so it is no longer used here.

But when I tried the JB Weld 5 min Plastic Bond on a JD hood it didn't even hold after letting cure overnight. But the Permatek 5 min plastic weld work so quickly I barely got the hood back together. Since it was a trial run I didn't buy anymore of the product. And ABS plastic was on the list of bondable plastics. That same hood came back shattered but that was 10 yrs later and the Permatek bonded areas were still in tack. It just the UV killed the hood.

As for the scoring in the bearing area I did a Honda last year where the magneto side was seized to crankshaft. All I could was to ream it back to spec. But the scoring actually allow it area to better oil itself and have to see the Super Z back. The customer back ran it without oil due to the PTO side leaking severely.