Lotus Elan

Main Bearing Wear Photos

PostPost by: hbferrariguy123 » Fri May 10, 2019 4:15 am

img_4129.jpg and

While disassembling my Elan engine which I was told has only a few hundred miles on it, the main bearings show substantial wear, I think leaving them unusable. What could have caused the wear on the bearings? I need to determine the cause so I can correct it before I reassemble the engine. Any advice?
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PostPost by: 2cams70 » Fri May 10, 2019 5:22 am

Looks quite normal to me. Just bedding in wear. It's not the underlay. If in doubt use some plastiguage to measure the clearances. Be sure not to mix the shells up. Return them to the same positions from whence they came.
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PostPost by: rgh0 » Fri May 10, 2019 9:19 am

Could be to tight clearances or could be corrosion if the engine has sat for a while.with water in the oil. Also could have been insufficient assembly lube or no oil pressure on startup.

Having got to this point I would replace them as they are not expensive and check clearances of the new bearing shells with plastigage.

The crank should not have been damaged but have a close look and measure to ensure the journals are round and highly polished and not marked

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PostPost by: 2cams70 » Fri May 10, 2019 9:49 am

There are no scratch marks on those bearing surfaces from running insufficient clearances. My guess is that it could be just staining from a Moly assembly compound. On the back of the bearing there should be the identification mark of the manufacturer and the bearing compound used. I suggest you contact the bearing manufacturer for advice.
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PostPost by: avro » Fri May 10, 2019 8:20 pm

I would suspect that having looked at the condition of your bearings the engine has been sat around unused for some considerable period of time. Competition bearings (tri-metal) have a very thin overlay of lead indium (usually between .0004? - .0008?) and this gives the bearings a superior surface finish . However compared to the basic steel aluminium bearing this overlay is more susceptible to damage from moisture especially if the engine has sat around unused.

I recently stripped some old Ford Pre Crossflow engines ( They had 701M ?L? blocks ) that had been reconditioned in the 70s for the Ministry of Defence but had never been used. Those fitted with the basic steel aluminium bearings looked almost as new, but those fitted with the lead copper bearings had the appearance exactly like yours.

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PostPost by: hbferrariguy123 » Fri May 10, 2019 11:40 pm

Nick, I think you hit the nail on the head! The engine was rebuilt in the '90' then used for a very short time then it sat for years before I bought it. Whatever the cause I will be replacing the bearings, following Rohan's advice and common sense.
I'm just glad it wasn't the result of a poor line bore or something of that nature. As Rohan said new bearings are inexpensive so I'll replace them along with measuring the clearances with Plastigage.
Thanks to all for your advice!
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PostPost by: 2cams70 » Sat May 11, 2019 1:52 am

See attached article regarding bearing staining. Seems to explain it all.
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PostPost by: baileyman » Sat May 11, 2019 2:09 am

avro wrote:I would suspect that having looked at the condition of your bearings the engine has been sat around unused for some considerable period of time. Competition bearings (tri-metal) have a very thin overlay of lead indium (usually between .0004? - .0008?) and this gives the bearings a superior surface finish . However compared to the basic steel aluminium bearing this overlay is more susceptible to damage from moisture especially if the engine has sat around unused.

I recently stripped some old Ford Pre Crossflow engines ( They had 701M ?L? blocks ) that had been reconditioned in the 70s for the Ministry of Defence but had never been used. Those fitted with the basic steel aluminium bearings looked almost as new, but those fitted with the lead copper bearings had the appearance exactly like yours.

Nick



Does this mean there may be no way to revive such an engine and avoid the bearing problem? I have a fresh engine that has been dormant for several years that I hope to use. It would be nice to avoid additional work on it.

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PostPost by: avro » Sat May 11, 2019 12:13 pm

John

For the price of a sump gasket set and a little time it might be wise to at least check them.The bearings may well be perfectly OK but it they?re not , changing them does not mean having to take the whole engine apart. The rod bearings are a little easier than the mains to fit. Once the big end cap ( one at a time ) has been removed, just turn the crank a very small amount to give a little slack on the journal and you can then use a clean flexible feeler gauge blade to push the shell around and out. Carefully slide the the new shell into position making sure that the tang of the shell bearing has fitted neatly into the keep.
The mains are a little more difficult as you will need to lift the crank just a very small amount . This means slackening the timing chain just a little. There is sufficient flex within the front and rear oil seal to achieve this without risking any damage to the seals. Use the feeler gauge blade for the main bearings in the same way .

Nick
Last edited by avro on Sat May 11, 2019 10:12 pm, edited 1 time in total.
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PostPost by: Billmack » Sat May 11, 2019 6:15 pm

Did you measure the thickness of them or you just dont like the color? If you measured how much difference across the shell?
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