3 5/16th pistons
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=55044
Printed Date: 10 Sep 2025 at 5:12am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: 3 5/16th pistons
Posted By: MilesGray (CO/KS)
Subject: 3 5/16th pistons
Date Posted: 10 Aug 2012 at 11:26am
Recently, I put rings in my 48C. I ended up installing used pistons in it also as the pistons in the tractor were 3 5/16 pistons. I now have 3 (cause I broke one) aluminum pistons that are 3 5/16 that are in good condition for sale. However, that is not my main reason for this post. It looks like the person who did this, who was two owners ago (I called the previous owner and talked to him about it); had a miscellaneous set of pistons laying around and needed to change pistons so he used them. I was wondering what, if anything that Allis used as an engine used these pistons? Once I put the 3 3/8 pistons in with the correct rings (which were the correct size of the rings, 3 3/8) in the tractor is starts and purrs nicely with no smoke after I replaced them. It actually runs about 100 times better than before, much quieter and idles with no misses from low to high. Before it would not run below the third notch. Wondering why you would put undersized pistons in an engine that you were going to use for actual work??? Sorry for the long post! Miles
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Miles Gray (CO/KS)
5 1938 B's, 1940 B, 1944 WF C, 1948 NF C, Gleaner A, White Top Rotobaler, 1957 IH Golden Jubilee... I'm either a collector, or crazy!
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Replies:
Posted By: Lonn
Date Posted: 10 Aug 2012 at 11:57am
Shouldn't they be 3 7/16" for an aftermarket piston?
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Wink
I am a Russian Bot
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Posted By: MilesGray (CO/KS)
Date Posted: 10 Aug 2012 at 1:02pm
Yes, but when I pulled them to do the rings, I didn't even measure them until after I had broken one trying to put the rings in. Why would I even think they were the wrong size! lol! These pistons that I took out are definitely 3 5/16 in diameter Aluminum pistons, the sleeves are 3 3/8. Except for the farmer installed 3 point and changed to 12 Volt with alternator, this tractor is original, including the PO #1 paint.
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Miles Gray (CO/KS)
5 1938 B's, 1940 B, 1944 WF C, 1948 NF C, Gleaner A, White Top Rotobaler, 1957 IH Golden Jubilee... I'm either a collector, or crazy!
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Posted By: Lonn
Date Posted: 10 Aug 2012 at 1:26pm
I was talking cylinder bore at 3 7/16". I don't know what a standard piston measures. It's usually the bore when a dimension is given.
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Wink
I am a Russian Bot
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Posted By: SteveC(NS)
Date Posted: 10 Aug 2012 at 2:02pm
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Aside from never having heard of 3 5/16" pistons. I wouldn't think an engine would run with 1/16" clearance between the pistons and the bores, If it did it wouldn't do so for long.
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Posted By: MilesGray (CO/KS)
Date Posted: 10 Aug 2012 at 2:12pm
It did work for about 2 years, the cylinder bore is 3 3/8 and the rings he used with the cylinders were 3 3/8 so it did seal (sort of) probably would have been fine if I wasn't actually using the tractor for what it was intended for! lol. it would have been fine for tractor rides and parades!
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Miles Gray (CO/KS)
5 1938 B's, 1940 B, 1944 WF C, 1948 NF C, Gleaner A, White Top Rotobaler, 1957 IH Golden Jubilee... I'm either a collector, or crazy!
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Posted By: Lonn
Date Posted: 10 Aug 2012 at 2:40pm
I think it would be 1/32" clearance on each side if the bore is 3-3/8" and the piston is 3-5/16".
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Wink
I am a Russian Bot
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Posted By: MilesGray (CO/KS)
Date Posted: 10 Aug 2012 at 3:06pm
I could definitely see the gap when I looked but of course I wasn't thinking about that when I started, just trying to get it finished. wasn't thinking about changing pistons and rings at the time.
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Miles Gray (CO/KS)
5 1938 B's, 1940 B, 1944 WF C, 1948 NF C, Gleaner A, White Top Rotobaler, 1957 IH Golden Jubilee... I'm either a collector, or crazy!
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Posted By: SteveC(NS)
Date Posted: 10 Aug 2012 at 6:13pm
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Of course your right Lonn. Even with the stock 3 3/8" rings I'd be curious to know what the compression would have been. I'll bet it cranked reaL EASY. Glad you're happy with the results of the proper assembly.
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Posted By: MilesGray (CO/KS)
Date Posted: 10 Aug 2012 at 6:30pm
I'll check compression next time I'm there and let you know, at least what it is now...
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Miles Gray (CO/KS)
5 1938 B's, 1940 B, 1944 WF C, 1948 NF C, Gleaner A, White Top Rotobaler, 1957 IH Golden Jubilee... I'm either a collector, or crazy!
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Posted By: SteveC(NS)
Date Posted: 11 Aug 2012 at 6:58am
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Miles, don't bother checking the compression for the correct pistons/liner installation for me now, I was just curious as to what it was ?
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Posted By: MilesGray (CO/KS)
Date Posted: 11 Aug 2012 at 7:42am
I don't think I ever did the 48, the 44 was 22 -27 when I took it apart to clean out the Gear teeth from the governor and timing geer...
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Miles Gray (CO/KS)
5 1938 B's, 1940 B, 1944 WF C, 1948 NF C, Gleaner A, White Top Rotobaler, 1957 IH Golden Jubilee... I'm either a collector, or crazy!
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