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Unread 05-02-2010, 07:59 PM   #1
Denver
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Join Date: Apr 2010
Location: mercersburg
Posts: 10
how to tell the year of 4.2

recently bought a 4.2 for second jeep that i rebuilding how ever dont know if it is a earlier 70's motor or if it is a 80's motor/ because the size of main and rod bearings changes any input would greatly help... thanks you all...

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Unread 05-02-2010, 08:47 PM   #2
EngChase
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1980 CJ7 
 
Join Date: Jul 2009
Location: NC
Posts: 255
post a pic, that will help for starters, and look for casting numbers.
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Unread 05-02-2010, 10:20 PM   #3
Drednot
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1991 YJ Wrangler 
 
Join Date: Aug 2005
Location: phoenix, az
Posts: 1,273
Look for the numbers stamped on the pad between #2 and #3 sparkplug

then refer to this page to decode

http://street2mud.com/webfiles/AMC%20Engine%20codes.pdf
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