Farm Equipment - 426 compression ratio

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426 compression ratio

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=209685
Printed Date: 12 Jan 2026 at 4:41pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: 426 compression ratio

Posted By: 8070nc
Subject: 426 compression ratio
Date Posted: 12 Jan 2026 at 9:55am

This is a mental experiment and i should probally quit thinking so much. I have a DTA 466 with a p pump in a medium truck. It will start in 20 degree weather like its summer. Its my understanding that those engines are 17to one compression. Would it be possible to have a set of pistons made for a 426 allis to raise the compression and what problems could that solve ir create

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1984 80780
1957 D14
DES 300 with 25000 engine
616 tractor

Replies:

Posted By: DrAllis
Date Posted: 12 Jan 2026 at 11:03am

I'm sure you could have custom pistons made with a few less cc's in the bowl, raising the compression to improve cold starting. Higher compression ratios are harder on the crankshaft, conn rods and all bearings. If you took two identical engines (except 16 to 1 and 17 to 1) and loaded them at 100% load until something failed, the 16 to 1 will run more hrs. it's a compromise. To get one thing, you might have to give up something else. DT-400 series have larger diameter mains and rods bearings. M & W piston kits from years ago did start as good as an IH and some on here can attest to that. Don't think you can buy them anymore.

Posted By: NEVER green
Date Posted: 12 Jan 2026 at 3:35pm

Throw in some total seal gapless second rings and bam!!

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2-8050 1-7080 6080 D-19 modelE & A 7040 R50