8070 Cankshaft problems?
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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=14822
Printed Date: 03 Feb 2025 at 12:51pm
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Topic: 8070 Cankshaft problems?
Posted By: randy
Subject: 8070 Cankshaft problems?
Date Posted: 06 Jul 2010 at 5:56pm
A mechanic told me that he had heard of crankshafts breaking on 8070s. I have never heard of this, has any body heard of this problem? I am doing a out of frame overhaul and just wondered if this is a problem? thanks Randy
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CA WD WD45 D17 D17 Diesel 7060 8050 8070
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Replies:
Posted By: DonDittmar
Date Posted: 07 Jul 2010 at 6:50am
yOU KNOW, i HAVE HEARD THIS RUMOR ONCE MYSELF, BUT HAVE NEVER ACTUALLY SEEN IT. MAYBE DR. ALLIS WOULD KNOW
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Experience is a fancy name for past mistakes. "Great moments are born from great opportunity"
1968 D15D,1962 D19D
Also 1965 Cub Loboy and 1958 JD 720 Diesel Pony Start
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Posted By: ORANGE FARM
Date Posted: 07 Jul 2010 at 7:16am
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I WOULD HAVE THE VIBRATION DAMPER CHECK. THEY DO GO BAD.WE HAVE THEM CHECK EVERY COUPLE OF YEARS. IF THEY GO BAD, THEY WILL BRAKE THE CRANK SHAFT.
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Posted By: smuggler
Date Posted: 07 Jul 2010 at 9:11am
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I personaly have never broke a crankshaft. We turn between 6500 and 7000 rpms have ran it with the dampner and currently dont use the dampner. And have never broke one.
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Posted By: wayneIA
Date Posted: 07 Jul 2010 at 9:25am
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What I was told by the local AC dealer was to make sure that the dampner is in good shape, and it is best to install new rod bolts since they are very prone to breaking on most of the 426 engines.
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Posted By: smuggler
Date Posted: 07 Jul 2010 at 9:36am
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I have taken alot of stock 426s apart with spun rod bearings and have never seen rod bolt failure.
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Posted By: Calvin Schmidt
Date Posted: 07 Jul 2010 at 9:46am
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When I bought my D-21, there was a rod hanging out of the block. The rod bolts that I bought from AGCO (after trying to source ARP rod bolts through my local speed shop) have ARP stamped on the head. That gave me alot of confidence. ARP bolts are much stronger than anything that ever came out of West Allis.
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Nothing is impossible if it is properly financed
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Posted By: smuggler
Date Posted: 07 Jul 2010 at 10:06am
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Well in my personal opinion rod bolts are usually not the problem its bearing failure. Which is a very common problem with the 426. spin a bearing rod grabs crank and sumthing has to give.
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Posted By: randy
Date Posted: 07 Jul 2010 at 10:47am
i have new head bolts and rod bolts, lookslike this engine was run hot, radiator was pluged so i am doing a out of frame overhaul! Bearings looked good and crank looks good, mearured on high end of journal measurments.
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CA WD WD45 D17 D17 Diesel 7060 8050 8070
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Posted By: DrAllis
Date Posted: 07 Jul 2010 at 12:03pm
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8070's weren't known for breaking crankshafts....7080/7580's were. Be sure to have your crankshaft magnafluxed by someone who knows where to look and especially on the nose just ahead of the gear. The cranks with a "keyway" for the front pulley would crack at the keyway area. Anytime there is a broken crank AND a broken main cap, the broken main cap caused the crank to break due to no support. I had an F2 combine years ago with the little 4 banger that broke a crank with less than 100 hrs on it and there was a broken main cap next to the break on the crank.
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Posted By: randy
Date Posted: 07 Jul 2010 at 12:57pm
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How do you check a damper, i emailed the mfg. and am waiting for a reply?
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CA WD WD45 D17 D17 Diesel 7060 8050 8070
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Posted By: Kcgrain
Date Posted: 07 Jul 2010 at 2:33pm
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I wish I knew how all these "BS " rumors got started, was it a John Deere salesman or an IH rep, maybe some farmer whose cousins, uncles best friends hair dresser sister had one that broke, been with 426 engines for 35 yrs now, over hauled a bunch of them seen them clock 20,000 + hrs with moderate care, yet the only one I have ever seen personally come apart was one that had 5000 hrs on and had been repeatedly cooked for 2 yrs prior, when it finally siezed a piston and broke the cap off of the rod ( must be the rod bolt failure) and came out the side. Where does this rod bolt failure crank failure BS come from, it just isnt true. Have friends that run an est 1000+ hp on a super farm tractor on a stock AC crank, so a 170 hp is gonna break it or the rod bolts?????Pure BULL S**T . Reminds me of a farmer I met 3 yrs ago with a shed full of new JD equipment, and when he found out that I was an AC man he went on to tell me what junk they were he "said he had D-21 thru to the 7050 and they were nothing but junk and constantly broke down, I tried to ignore him for the first 15 minutes of his BS but finally couldnt handle it any more so I said well if they were so prone to failure what was failing the engines, his answer was no, the trannys? no again, the rearends tear them apart, well no, so I said what was the problem the headlights burnt out, the blinker fluid leaked ???? What be specific, when push came to shove it turned out he never had an AC was his neighbors and he heard he had all these problems..............yeah right.
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Posted By: Gary(WI)
Date Posted: 07 Jul 2010 at 3:14pm
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Polk Diesel in Madison Can Check viscous damper I do not of a way to check to other style but There used to be a place in California that would re pour the rubber ones Gary
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