History

• The Chevy standard-performance 307-cubic inch engine was produced from 1968 through 1973 as a successor to the 283-cubic inch engine. Both these engines have the same diameter cylinder bore---3.875 inches--and used the same cylinder head design. Many other components were interchangeable, as well. However, the 307 used a crankshaft that had a 1/4 inch longer crankshaft stroke---3.25 inches--versus the 283's 3-inch stroke.
  
  

Differences

• Aside from the longer stroke, the main and rod journals of the 307 crank were enlarged to 2.45 and 2.1 inches, respectively, from the 2.3- and 2-inch journals of the earlier 283s. This makes them incompatible with the early 283 blocks. The 307 crank was also used in the '68 and '69 4-inch bore blocks to yield 327 CI. (Pre-1968, 327 small-journal cranks could be used in early 283 blocks to "create" a 307 CI engine.)
  
  

Specs and Identification

• All '68 to '73 307 cranks (shared with the late 1960's 327 CI engines) were made of cast iron and were internally balanced. Casting ID numbers for the 1968 to 1973 307 and 327-cubic inch engines are 1130, 4672, 3911001, 3911011 and 3941174.