D12 Woes
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=131903
Printed Date: 01 Jun 2025 at 8:06am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: D12 Woes
Posted By: Jeeper38
Subject: D12 Woes
Date Posted: 27 Nov 2016 at 9:47pm
I started working on my D12 engine back in October. I've ended up doing basically an "In Frame" overhaul plus having the head gone through. Today I pulled the sleeves and then changed the main bearings. Standard bore bearings came out and the same size new went in. Afterwards, the engine wouldn't turn. I took them out cleaned things real well and then went back together again with thinner oil just to see if that would fix it but it still wouldn't turn. So, I took the new bearing out and put the old ones back in and it STILL wont turn. Does anybody have any experience with this. Could the Crank have moved or something to but it in a bind? Wishing I had left the mains alone at this point. They didn't even look bad. I just figured do them while I'm in there.
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Replies:
Posted By: DiyDave
Date Posted: 28 Nov 2016 at 5:24am
| Got your pistons in in the correct position? Look in your shop manual, there is a notch in the piston tops, I think it faces toward the front of the motor...> |
Posted By: Brad-MN
Date Posted: 28 Nov 2016 at 5:43am
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Plastigage the bearings to make sure you have the correct clearances all the way around on them. ------------- 1930 U 1938 A 1941 WF |
Posted By: Butch(OH)
Date Posted: 28 Nov 2016 at 7:54am
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I assume that the pistons and rods are still out of the engine?? If so and since the original bearings wont work either I would guess that you have installed one or more of the main caps backwards or on the wrong journal, or you dinged the shells when you rolled the uppers in. The caps must be on the same journal you removed them from AND the same direction, check that. Also look for heavy scuff marks at the bearing parting line. That is wear the missmatch occurs when you have switched the caps or installed them backwards. A way to tell which way the caps should be installed is to look at the locking tabs, both upper and lower should be on the same side. |
Posted By: Jeeper38
Date Posted: 28 Nov 2016 at 8:21am
| The bearing tabs go on the same side? I was positive they go on opposite sides. I know each cap is in the same spot but I put the tabs opposite each other. I thought they came off that way. Ill try that tonight and check my book again to see what it says. |
Posted By: Butch(OH)
Date Posted: 28 Nov 2016 at 10:37am
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That is your problem, you put the caps on backwards. |
Posted By: Jeeper38
Date Posted: 28 Nov 2016 at 11:42am
My uncle is at my shop putting the caps on as described by Butch(OH). He also checked the book which agreed with what you said about the caps. Thanks for pointing me in the right direction. If he gets the crank issue fixed then I'll be ready to drop in the new sleeves and pistons tonight.  |
Posted By: Jeeper38
Date Posted: 28 Nov 2016 at 12:13pm
| My Uncle just got a hold of me and said that with the main caps corrected it turns great. Thanks for the idea Butch. Looks like ill start sleeves tonight. |