What heads come on the GM Vortec crate engine

[BOTTLEDZ28]

GM offers two different new Vortec crate engine replacements. One for 1/2 tons and the other for 3/4 and 1 ton trucks. AKAIK, the only difference is the 2 bolt versus 4 bolt main block.

But I heard that GM used two different Vortec heads. The 062s and the 906s. Super Chevy did an story about these heads and said that some ¾- and 1-ton trucks came with Vortec heads equipped with a specially hardened exhaust seat that kills low- and mid-lift flow. Casting number 10239906 should be avoided.


Does anyone have an input on this? I wonder if the two replacement engines have two different heads.

 

[MIHELA]

I may be able to check tomorrow if I have time. Keep in mind that both crates are Mexico built and do not have the same casting numbers as the old ones. The ports are a hair smaller.

 

[BOTTLEDZ28]

I may be able to check tomorrow if I have time. Keep in mind that both crates are Mexico built and do not have the same casting numbers as the old ones. The ports are a hair smaller.

So GM has a third different Vortec head out which is worse than the ones on my engine now?

 

[884x4310ci]

The 906 available on the 3/4 ton and 1 ton had a different valve job on the exhaust side. That's about it.