8070 Cylinder Head Cracks
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=198952
Printed Date: 16 May 2025 at 10:51pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: 8070 Cylinder Head Cracks
Posted By: CJSuhr
Subject: 8070 Cylinder Head Cracks
Date Posted: 29 Dec 2023 at 7:53pm
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I am overhauling a 8070 426 670I engine. I have taken two yonder heads to my local machine shop and both have been crack checked and failed. The first one has a crack in at lease 3 of the 6 injector holes, hard to see in the pictures. The engine it came from had melted part of the #4 piston and had been hot at least once In the past. The second one has cracks between both the valve seats. The engine this one came from had serious detonation damage in 3 if not more of the cylinder/pistons, and was getting water into the engine oil. I am still working on trying to locate another cylinder head to try, but If I cannot find one I need to figure out with is by better bet to try to use. Both need about the same amount of work as far as guides, seats and valves. I know some JD heads can have “stress cracks” in areas like the injectors holes and run just fine for years. I am leaning on using the first cylinder head with cracks in the injector holes but want to get others opinion on here if they have had any similar experiences. Hopefully the pictures load up right, but the close up of the injector holes are of the first head, and the zoomed out picture is of the second head. The injector hole cracks are very fine and hard to see, zoom in if you’re having trouble.    
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Replies:
Posted By: DougG
Date Posted: 30 Dec 2023 at 7:31am
| I believe I seen one on Ebay the other day - pretty sure it was for a 426 |
Posted By: Gary(WI)
Date Posted: 30 Dec 2023 at 7:35am
| I have a couple I would sell 450 I can crack check it before you get it. |