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Journal defect - big end

Fireblade

Active member
My work on cleaning up the crank for my R5Alpine engine rebuild came to an abrupt halt when I noted this defect on the the No 1 big end journal. Is this a deal breaker? ie I'm not keen on doing a regrind - would rather find a crank in better condition to start with. To me, it looks like a fault when the engine was last/first built, not acquired during use.

I've also attached photos of the bearing shells - all showing significant wear and fatigue and some crap that went around in the oil - but to me, none look like a bearing "fail" and I am curious if you can pick the shell that was on the journal with the defect (they are not in order!)

IMG_1635.jpg
IMG_1636.jpg
 

COL

Alpine A110
How deep do you think that blemish is? Regrind sizes are 0.25, 0.50, 0.75 & 1.00 mm under standard size.

I would take to an engine machine shop and get their advice.
 

Fireblade

Active member
The blemish looks largely in the shadow of the oil feed and it is also "downwind" of the power stroke so to speak - if this makes any difference
 

Fordman

1000+ Posts
The blemish looks largely in the shadow of the oil feed and it is also "downwind" of the power stroke so to speak - if this makes any difference
I believe it does make a difference, which is why you cant see much difference in the shells, it is in a no-load area.
If that was mine, I would be more inclined to go by the micrometer diametric measurements in at least 4 places on each journal, and if there is no measurable wear, re-use the crank. If it was an aircraft, or a racing engine, I would not, but I don't think that imperfection would cause a crack to occur in normal use.
However, it will always be on your mind, so probably needs to be excised in some way, or replaced - presumably a modern day crank grinder is capable of restoring that like new.
I wonder if it may have been caused by a previous serious failure, eg, big end/conrod failure?
Just my opinion.
 

Artificer

Active member
If the crank measures correctly, what is all the fuss?

The bearing shells & associated oil film/s are over a huge area compared with that minute spot.
As long as the area is not raised above the rest of the crank, then no problemo.

If a raised area was the case [& it isn't apparently] carefully oil stone down that area until it is round & level with the rest of the journal.

That [raised] being the case & there would be evidence of an issue on the removed bearing shell. They all look similarly worn to me.
JG.
 

alan moore

1000+ Posts
I would guess it was the third shell. Looks like a small dint in the journal surface that now has a small raised area around it. I would linish/polish the crank and re-use it with no fear. I do think the slightly raised area around the dint should be removed.
 

COL

Alpine A110
If Fireblade is going to use that crank, it would be a good idea to linish all the bearing surfaces. Doesn.t matter if its professionally done or DIY.

If you DIY look at this video
 

Fireblade

Active member
I would guess it was the third shell. Looks like a small dint in the journal surface that now has a small raised area around it. I would linish/polish the crank and re-use it with no fear. I do think the slightly raised area around the dint should be removed.
Alan - you are spot on - it is the third shell (counting from the left)! I'll have to find a prize for you!
 

jaahn

1000+ Posts
Hi :)
My comments. I have 'liked' some comments made by others above. I would think that it looks like something may have been dropped on it previously. It is not a flake or bearing failure. AND it is insignificant compared to the big oil hole drilled into the journal just next to it and going right through the crank to the main bearing. LOL.🥴
It is on the opposite side to the power side and the bearing shells show it is not causing unusual wear compared to the "perfect" journals. So mike the blemish and if it is proud stone it off gently , cannot be much if at all. Linish it if you want, but if the sizes mike OK not worth grinding it IMHO. ;)
Jaahn
 

Whippet

Active member
I think that that the proof lies in the bearing shells, they look OK to me. I wouldn't be to concerned with the small recession, but more concerned about the displaced material around the periphery that sits slightly proud of the journal surface. That said, the blemish is very small compared to the lubrication holes adjacent. It has been OK up until you became aware of it and if you don't want to regrind the crank I consider you could proceed. Asking an engine builder if you need a regrind is a bit like asking a barber if you need a haircut - they will always say "of course sir, come in".
 

schlitzaugen

1000+ Posts
If you want it repaired but do not want it ground down to the next size, you can have it spray welded and reground to the same size (or even original factory size). Ask around where it can be done. I have had rocker shafts repaired that way and they came up very well. The machinist can advise how to go about it.

Agree with suggestion above, it looks more like someone dropped a hammer on it than an engine failure.
 

Fireblade

Active member
Thanks everyone for advice. I have gently knocked down any high spots (with a file as per youtube) and will confirm specs with a micrometer - if it all comes up good, I am more than happy to pop it back in service.

Best Regards to all,

George
 

Whippet

Active member
Hi, If you have dressed the high spots with a file, you need to linish the affected area. Its bee to many years since I did this, so cant advise what grit wet & dry to use.
 
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