7080 rod bearing wear
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=106212
Printed Date: 11 Sep 2025 at 9:46am
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Topic: 7080 rod bearing wear
Posted By: LB0442
Subject: 7080 rod bearing wear
Date Posted: 15 May 2015 at 8:35pm
A few weeks ago I bought a 7080 that has been setting a long time, was told it did run though just has a trans leak. I have made quite a few trips to the junkyard for my other tractors and one thing I see a lot of is the 426 engines with a rod poking through the side of the block. It seems to be #4 is the likely one. I felt that since this one has the non ventilated block I would replace the rod bearings and check the mains. Liners all looked good from the bottom. I bought the federal mogul bearing FP-3470CPA and rod bolt kit 70277489. The instructions on the rod bolts tell you to rotate the piston /rod 180 so the bearing slot is facing the cam. A couple of these(the ones without the weights were easy) the rest - what a pain. You have to have the rod journal close to straight across from the cam and start the turn of the assembly and then turn the rod a little then turn the crank a little for clearance. Better make some extra time if you plan on doing this in the tractor like I did. Did get them all done though. The interesting part is the wear. The tach shows 4570 hours and did work after I got it done. #4 has the worst wear of the bunch. That's 4,5 and 6.
 I measured the new bearing shells and the old ones were between .002 and .003 smaller?? LOT of wear. The rod journals min per the manual is 2.7470 the worst of the 6 measured 2.7462, which is only 8 ten thousandths less than min, none were out of round. I even double checked my zero on the micrometer. The highest oil clearance the plastigage showed was .0035. The crank has w germany cast on it and that is a very well built crank to take the abuse of the worn out bearings and still looks perfect, no grooves just smooth as new. Just thought it was interesting to see the bearing appears to be the weak point. I did pull the last main cap(farthest from the oil pump and it looked great). Got it running and sounds great. |
Replies:
Posted By: MACK
Date Posted: 15 May 2015 at 9:25pm
| 5000 hrs are max for 426 bearings. I hope you changed the main bearings at the same time. MACK |