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Crankshaft Bearing Shims

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Old 09-26-2018, 08:32:42 PM
AR14949 AR14949 is offline
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Default Crankshaft Bearing Shims

Working on a continental model N 4 cylinder and trying to set main bearing clearance. By removing the factory shims the hole is no longer round and begins to take on an egg shape. Naturally I would think this would create slop and knock when running but if that were the case why would the factory put removable shims under the caps? Is it supposed to be line bored after removing shims?
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Old 09-26-2018, 10:38:41 PM
Bill Hazzard Bill Hazzard is offline
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Default Re: Crankshaft bearing shims

Very little wear occurs at the cap joint so removing the shims actually makes the bearing more round.
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Old 09-30-2018, 09:57:34 PM
Georgia SS Georgia SS is offline
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Default Re: Crankshaft bearing shims

Hey Guys
Not much response about crank. bearing taper shims, I suspect most of the posters are not old enough to know what they are, used several back in the years, think shims wer sometimes used at the factory to correct a machining screw up, like mayb GM did on early 327 Small Block main bearings, was running down at the old Jacksonville Fl. speedway back in early 60, locals ran some monster engines (Pontiac), saw Smokey Eunick take checks from his check book and cut and stack behind the bearings to take up the slack and that was Smokey the legend engine builder, he also had a side kick Speedy Spears that was bad to the bone, true pioneers of racing, talk about good old days.
Take Care
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Old 09-30-2018, 10:36:32 PM
M.Canute M.Canute is offline
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Default Re: Crankshaft Bearing Shims

I was chatting with a friend a couple of days ago and he was telling me about an old 1950's Ford automobile engine he was disassembling. He said some previous owner had shimmed the bearing shell on the main caps which were worn down to the copper. The engine side was not shimmed.
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Old 10-01-2018, 12:06:02 AM
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FWurth FWurth is offline
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Default Re: Crankshaft Bearing Shims

Yeah, shims under the insert was an old trick used to tighten up badly worn inserts. This was usually done to get things good enough to sell it, without spending any money to fix it right.
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Old 10-02-2018, 06:55:14 PM
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grub54891 grub54891 is offline
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Default Re: Crankshaft Bearing Shims

An old timer up this way actually whittled out a bearing for his motor.
Then drove to the dealer and traded it in for a different vehicle.
The dealer found the wood bearing after selling the car, when it threw a rod.
They were not happy.
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Old 10-03-2018, 12:11:52 AM
Oldtech Oldtech is offline
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Default Re: Crankshaft Bearing Shims

Mr Hazzard is correct. No problem removing shims to tighten up mains. remove til it binds then put one back in.
Another old trick used - and shouldn't have been was to file the caps. not accurate enough but yeah, i've seen it done.
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Old 10-03-2018, 01:36:40 PM
Andrew Mackey Andrew Mackey is offline
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Default Re: Crankshaft Bearing Shims

I have seen some strange things for shims and bearings! One friend bought a model T car. He told ma that under a load, it made a strange thumping sound from the engine. I pulled the pan and found that instead of Babbitt bearings, a leather belt was under all four rod caps! on another engine, news paper was used for shims. It squashed out and the caps loosened -made a mess out of the crank and rods.

I have been working on 2 Jacobsen Twin engines. They have different con rods. On one engine, the rod and cap are machined to a polished surface. there were shims to space the rod cap properly. The other engine had rods and caps that looked like they were milled. You could see the machine turnings on the rods and caps mating surfaces. No shims there, just a perfect fit on the bearing to the crank.
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