Farm Equipment - 426 cylinder heads

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426 cylinder heads

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=194646
Printed Date: 02 Oct 2025 at 1:50am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: 426 cylinder heads

Posted By: Kevin210
Subject: 426 cylinder heads
Date Posted: 16 Apr 2023 at 12:38pm

Is there any difference between a head off of a 3500 engine compared to a 3700 engine,just curious.There is a reason behind why i would like to know but it's embarrassing LOL.

Thanks..

Replies:

Posted By: DrAllis
Date Posted: 16 Apr 2023 at 12:47pm

If the casting numbers are the same, they are the same. There was a time in late 1974 and maybe thru 1975 that a 7080 had a different casting number than the lower HP 7040/7060 engines being built on the same day. The 7080 head had .100" more iron in it on the bottom deck for durability. As time went on, all 426 engines received the newer/thicker head regardless of HP output.

Posted By: Kevin210
Date Posted: 16 Apr 2023 at 1:00pm

Thanks Doc.
What I did was used the head off my 3500 engine
and put it on a MK II 3700 engine...
So this is somewhat hind sight I guess you could say..

Posted By: DrAllis
Date Posted: 16 Apr 2023 at 1:29pm

Well, there are 3500 heads from 1966 and 3500 Mark 2 heads from 1973 and 1985. Newer casting numbers usually yielded durability improvements.