Preparing bearing shells in a Twin spark? - Alfa Romeo Forum
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(Post Link) post #1 of 9 Old 07-06-16 Thread Starter
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Preparing bearing shells in a Twin spark?

Hi Guys, I have the sump off my 156, as I have traced my engine rattle to the bottom end. To be honest it was diagnosed by the nice chap from Italia Speed (Nr Newbury) .

Fingers crossed its just shells but I haven't got the rods apart to check yet. If it is just the shells apart from cleaning mating surfaces do I need to use any special lubricant between the shell and crank?

Most threads I have found bang on about the difficulty of getting the sump off (agreed!) but give little away when it actually comes to changing the shells!

Any thoughts/advice greatly appreciated!
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clean ..very clean , operating on a brain clean , oil , plain oil ...clean ..so very clean .
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Graphogen, sparingly. Will give lubrication prior to the oil itself getting there. Will darken your oil but not harm anything.
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Most people seem to suggest that clean engine oil is perfectly adequate.

You can soak the shells in the oil for a while before you fit them, then squirt it on the big end journals before assembly.
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Assembly lube to be safe.
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(Post Link) post #6 of 9 Old 08-06-16 Thread Starter
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Thanks for the responses people. I shall stick a proper thread together with some wonky pictures in it, when I get this job completed!
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And if I were you I'd disconnect the coils and crank the engine a few times so oil reaches the bearings before you start it.
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I use a paste made of graphite grease ands engine oil. Seems to do the job.
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(Post Link) post #9 of 9 Old 13-06-16 Thread Starter
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Another slightly daft question for you guys... I have measured the crank journals and the diameter and thickness of the bearing shells. The Journals are between 50.8mm and 50.7. The thickness of the shells seems to average out around 1.4 mm, maybe 1.45 mm in the centre and about 51.1mm across. Part number is 46738752 if your interested!

I was sent a pdf from my local Alfa dealer with about 6 different bearing sizes for the engine, seemingly ranging in thickness between 1.527 mmto 1.59mm. Does 50.8 sound like a standard crank size? If it is then I guess I am looking at the smallest size at 1.527mm and the fact that my shells appear skinnier is poossibly down to wear over 93k miles?

Thanks again!
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