Piston Question
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=48662
Printed Date: 26 Aug 2025 at 12:59am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Piston Question
Posted By: hamman01
Subject: Piston Question
Date Posted: 08 Apr 2012 at 3:10pm
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I was just noticing today that the 1942 WC I have has dished top pistons in it. My son's 1947 Wc has flat top pistons. I've heard of "Power Crater" pistons in the WDs but not in the WC. Anyone have an Idea on this? I have the engine down in the 42 and I want to rebuild it. I have a engine from a 1952 WD to put in it this summer. Eventually I want to put the original back in. It was run on cold oil and spun some bearings and locked up. Thanks.
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Replies:
Posted By: Redwood
Date Posted: 08 Apr 2012 at 3:15pm
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It was common for the original pistons and cylinders to be replaced with the WD power crater pistons to increase the power of the engine. We have them in our WC and the original invoices for the replacement cylinders and pistons that are in the tractor. I expect yours has had the same modification.
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Posted By: DanD
Date Posted: 08 Apr 2012 at 7:29pm
I'm fairly certain that when new, the WD's also had flat pistons. The power crater piston did not come to be until the WD45. Also, if one takes a WD45 or even a D17 piston and uses it in a WD or WC with the 4" stroke, I believe the resulting compression ratio is so low that poor performance is the result. I think this has been a fairly common mistake over the years. This applies to OEM pistons only. I'm sure there have been aftermarket pistons made for the WD and WC over the years that had some kind of dish in them. If I had a picture, I think I could tell if they were OEM Allis power crater pistons or after market. Also, measure to see if the pistons in your WC are 4" or 4 1/8" in diameter. If
4 1/8, then they are aftermarket for sure and what I said above about compression ratios above may not apply.
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Posted By: hamman01
Date Posted: 08 Apr 2012 at 7:39pm
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I will measure them tomorrow. When I took it apart I was the third owner of it. My brother the second. He never did anything to it as it wasn't running when he traded for it. The way it came apart made me think it was the way it was when it weas made. I will get some pics of them and try to post them on here. Thanks.
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Posted By: wjohn
Date Posted: 08 Apr 2012 at 7:57pm
What's the serial number on the block?
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1939 B, 1940 B, 1941 WC, 1951 WD, 1952 CA, 1956 WD-45
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Posted By: Kip-Utah
Date Posted: 08 Apr 2012 at 10:40pm
When you tear into this engine chances are that you may find that in addition to "crater style" pistons, you might also have a 4.5" stroke crank from a WD45 as well. This was a fairly common dealer or farmer installed update to the 201cid engines used in WCs & WDs. Kip
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HANSEN'S OLD ORANGE IRON. Showing, Pulling, & Going!!
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Posted By: hamman01
Date Posted: 09 Apr 2012 at 4:40pm
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Had some time to look at the pistons and engine today. Ser# W130240G. The pistons carry a number of 1728. The rods carry #s 56 and then at the end U9988. Any help would be appreciated. Thanks. Roger
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