Farm Equipment - block comparison-844 vs 731

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block comparison-844 vs 731

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=48961
Printed Date: 25 Aug 2025 at 8:15pm
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Topic: block comparison-844 vs 731

Posted By: Dale
Subject: block comparison-844 vs 731
Date Posted: 13 Apr 2012 at 9:17pm

I suspect I know the answer but here goes. Can a block from an Allis 844 engine be used to replace a block from a 731 Allis engine.

Replies:

Posted By: CAL(KS)
Date Posted: 13 Apr 2012 at 9:45pm

if your referring to the engine use in 8550 and 4W305 then i would say yes. major differences should be in crank (stroke) and compression height of pistons and maby rods not sure. otherwise only minor differences like exhaust manifolds (731 has 2) for twin turbo and different turbo piping. intake manifold maby be different for turbo piping also.

this would apply to later 844 blocks like 17000-25000 motors. early 16000 and 21000 and buda 844 blocks have smaller main journals. My 59 HD16 has 16000 and bearings are not available

i think the blocks are identical, hopefully some one who knows for sure will chime in.

the 731 is just a destroked 844

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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20

Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15

Posted By: DrAllis
Date Posted: 13 Apr 2012 at 9:48pm

I would guess ( and it is only a guess) that if they were both built new at the same time in history, they would be the same.

Posted By: tbran
Date Posted: 14 Apr 2012 at 9:04am

I have a block , 731 , out of an 8550 . Cheap.

Posted By: Dale
Date Posted: 14 Apr 2012 at 6:26pm

Might be interested in that. Can you PM me of the price and details. Thanks