how do you look for the difference in a 406 and 390

 

The 406 is a 4.13 bore and a 3.78 stroke. The 390 a 4.05 bore and 3.78 stroke. As far as ID goes the 406 is pretty straight foward. The 406 block castings were all 62 1/2 to 63 1/2 castings. Also their casting numbers were not duplicated by other bore blocks and all have the "HP" markings, solid lifters and oil pressure relief valve. Most have the crossbolt bosses and a few even crossbolted from the factory as rumored. Overall the 406 is very easy to ID if original or not by their block casting numbers. Heads except for the later C3AE-C's which were also 390 heads in different trim also easy to ID and have a C2SE-B or C casting number. Some of the early 390's are easy to ID and one of the more rare the 390HP which was the precurser to the 406 back in the day. Later 390 castings have the generic casting numbers but fairly easy to ID by wallcore thickness and bore size.

406 block castings to look for...
C2AE-J
C2AE-K
C2AE-V
C2AE-BD
C3AE-D
C3AE-V


G.