Just a suggestion....if you included a little bit more info on what you DO know about your vehicle/engine, some of the more knowledgeable guys might be able to help. My limited resources show the 6 digit casting numbers as being on some of the older engines. However, there were no 216, 235, 261 Chevy engines with the first number in the 4 series. I use the inliners info as well as:

http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/cast


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