Originally Posted by F-BIRD'88
You have to join the forum to read in the "advanced" section this is not the first mention of the difference in the new Mex cast heads.
Joe Sherman who comments in this forum thread is a internationally recognized custom racing engine Guru (among others that hang around this forum) that hase worked quite a bit on Vortec head combos and knows his stuff.
I have not personally flow tested the new Mex heads myself but have worked with the older OEM 062's that were made here in Canada and installed on the 96 to 2000 L-31 truck engines.
They flow tested at 228cfm in stock form with stock valves.
The data on this pages clearly shows the new vortecs (not the bowties) heads are down quite a bit.
Seems that every time I am on this forum I gain some more knowledge. I would have thought that any 062 casting from 96 on would be the same. So when we are taking L-31 it means from 96-2000 only. After that (2000) a 062 casting would be the mexico head and not really a L31? Thanks F-BIRD