Crank mains minimum dia

Doug 13 · Sep 24, 2022

My 8N manual does not give me the minimum diameter for the crank mains or the connecting rod journals. They have measurements for the out of round and taper. I think minimum diameter would be given. I know the clearance so I will use plasti gauge.

TheOldHokie · Sep 25, 2022

(quoted from post at 22:59:35 09/24/22) My 8N manual does not give me the minimum diameter for the crank mains or the connecting rod journals. They have measurements for the out of round and taper. I think minimum diameter would be given. I know the clearance so I will use plasti gauge.

That will be determined by the availability of bearings. .050 under is probably pushing the limit. You measure that with a micrometer.

If you are talking about maximum oil clearance that is .005/.006

TOH

This post was edited by TheOldHokie on 09/25/2022 at 04:20 am.

Den N Ms · Sep 25, 2022

Doug 13 , .060 over sized bearings
is the limit that I know of.

https://www.yesterdaystractors.com/Ford-8N_Main-Bearings-060-Oversize-Set_106257.html

John Deere D · Sep 25, 2022

I do the below when deciding on the UNDER-SIZE bearings I require...

With a micrometer, check Journal for all variations as in out of round and tape....
Then verify what undersized bearing shells are available....
Then have Crank journals machined to achieve your desired final Clerance .(inches)...ie... .001 .002 .003 .004 .005
Etc,etc,

TheOldHokie · Sep 25, 2022

(quoted from post at 10:38:29 09/25/22) I do the below when deciding on the UNDER-SIZE bearings I require...

With a micrometer, check Journal for all variations as in out of round and tape....
Then verify what undersized bearing shells are available....
Then have Crank journals machined to achieve your desired final Clerance .(inches)...ie... .001 .002 .003 .004 .005

Standard practice is the journal is ground to a fixed undersize (.010, .020, .030, etc) based on the manufacturing specification.

The oil clearance is built into the bearing. If you want to fine tune the oil clearance its done by selective fit of the bearings.

TOH

8NChris · Sep 25, 2022

(quoted from post at 19:59:35 09/24/22) My 8N manual does not give me the minimum diameter for the crank mains or the connecting rod journals. They have measurements for the out of round and taper. I think minimum diameter would be given. I know the clearance so I will use plasti gauge.

hen your ready to reassimble double check all the oil gallys. Some prefer mineral spirits, pipe brushes and a splash of denatured alcohol.

Doug 13 · Sep 25, 2022

Ok, thanks that's good info. I have a micrometer. I'm still a bit confused. The bearings size is probably marked on the back. I didn't get crank out today. I thought about just calling the crank good. I better check.

TheOldHokie · Sep 26, 2022

(quoted from post at 22:26:29 09/25/22)
Ok, thanks that's good info. I have a micrometer. I'm still a bit confused. The bearings size is probably marked on the back. I didn't get crank out today. I thought about just calling the crank good. I better check.

Pretty simple. From the factory mains were 2.248/2.249 and rods were 2.0935/2.0945. Standard undersizes are .010, .020. .030. .040 and .050 less than that.

TOH

This post was edited by TheOldHokie on 09/27/2022 at 03:24 am.

Doug 13 · Sep 26, 2022

Thanks TOH very good. That's the numbers I was looking for.
Looks like the crank pulley spun on the crank end. Must have got real loose. Scratched and scored a little. Hope that won't hurt me.
Thanks again to all. My first tractor overhaul.

Crank mains minimum dia

Doug 13

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TheOldHokie

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Den N Ms

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John Deere D

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TheOldHokie

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8NChris

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Doug 13

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TheOldHokie

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Doug 13

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