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Bearings cleaning and inspection

Practical Engine Building

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After seeing the Practical Engine Building and the Worked Examples I have some doubts:

1.- I notice that you use brake cleaner to clean the bearings, that does not remove the coating film? it can be use Gasoline too?

2.- Have you ever come across a bearing that has sharp or rough edges and burr in the oil channel as my photos show? If so, is there anything that can be done about it?

3.- I have heard that some engine builders use Steel Wool # 0 to clean the bearings, any comments about it?

4.- I saw that you use oil for bearings, is there any reason why you don't use assembly lube?

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Cristian hi,


Brake cleaner is used primarily in cleaning processes as it doesn’t leave any films; degreases and cleans a surface; using other products like gasoline for example can leave residue behind as there is normally additives inside gasoline. Try not to rub the running surface of the bearing and personally I just clean the back of the bearing shell and the block, not touching the running surface. I have seen some builders who wipe the running surface but this is not something I recommend personally.


Yes, unfortunately not all bearing manufacturers are equal and sometimes there can be some burrs created in the manufacturing process; this is a tricky one as it depends on the size of the burr; which was it protrudes (is it onto the running surface effecting rotation) and will it possibly come off. I have in the past deburred bearings you be overly sure; again not damaging the running surface and making sure there is 0 debris left afterwards, cleaning with brake cleaner.


I would never use steel wool in an engine; it could fragment and little bits of the wool could end up in galleries! I have used scotch brite to clean up the block as this doesn’t remove any material (microns) but I wouldn’t ever clean a bearing shell; if it needs this level of cleaning I would use another one.


When I was building engines which would be fired up within a day or two I would use the engine oil the engine would be running with. If I was building an engine which was going to be shipped or sat for a week or so I would use engine assembly lube. Thoughts being that the assembly lubes are normally very thick and sticky, staying on the journals and cylinders whilst in transit and help to protect on the first fire up. Remember that running an engine for the first time the oil should be changed quite soon as to remove any contaminated fluids; any tiny bits of debris.

Hope this helps!

1/ As Dave said, brake cleaner doesn't leave residue that petrol/gasoline and some other 'clearers' may leave behind. I usually use an electrical cleaner that is an iso-propanol based product.

IMPORTANT - this is the oil film and/or dirt - most bearings nowadays come with a film, or coating, on the journal side that is specially made to give improved properties - DO NOT clean this off!

2/ It does happen, but I haven't seen anything that bad in decades - what brand are they? You could clean them up with a fine file, but if the manufacturer's quality control is that poor, I'd be returning them for a more reputable product.

3/ Some traditionally use this on the back of the bearing shell - some, god forbid, use it on the load bearing side! - DON'T DO THAT, EVER! This is a bit of a carry-over from when some suppliers were less than good. DON'T do it - maybe a light clean of the back of the shell with a fine nylon abrasive pad, but make sure it is CLEAN afterwards.

4/ As Dave said, depends on how the engine is going to be used - if it's dry sumped, or has a belt driven wet sump pump, it takes just a moment to remove the belt and run the pump with an electric drill to thorougly prime the engine. Personally, I normally use a mixture of a smear of assembly paste and a couple of drops of oil.

Those are just my thoughts on the subject, though, so get as many views as you need.

Thanks Dave and Gord for your reply,

1.- Clear enought to use break cleaner too

2.- I'm using King bearing and I was really a little disappointed to see those burrs in some lubrication holes and the lubrication channel as seen in figure 1, maybe that does not limit the flow of oil to the other bearing but if we take time to polishing the oil conducts in the block for better flow we hope to have a product as important as bearings with perfect finishing. "I solved it by using a very fine file and being very careful, I never touched the bearing surface"

I also found that almost all bearings had shard edges on one side only (as shown in figure 2) these edges were felt when you ran your finger and it was very difficult to know if it was very close to the running surface, "I use 1000 sandpaper and very carefully and angularly pass it without pressure a couple of times, after that I cleaned it well and it felt smooth.

3.- My doubt now is that to clean the bearings use wypall towels with gasoline and rub the running surface removing the dark film a little and remaining 2 colors as shown in figure 3, in most cases bearings are most with the light color but this feel smooth.

4.- clear with that, good point, just wondering if would be better to use a break in oil (as Amsoil or Redline) for the ensambly intead of use a regular mineral oil.

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