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L31 vortec heads

257 Views 3 Replies 4 Participants Last post by  bondo
Are there any big differences in the two l31 vortec heads? My truck has the 062 and I need a reman pair. I received a 906 pair. I know they are the same but are there any differences between the two castings that I would like to know about?
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One is more commonly used in trucks, and is equipped with a hardened exhaust seat insert rather than just a induction hardening of the parent seat material.
I don't recall which # is which though....but you can easily spot the hard insert as it leaves a small lip just below it in the valve bowl that hurts flow a tiny bit.
Otherwise, the heads are the same.
The 906 has a little different configuration where the exhaust pocket merges into the valve seat to provide improved support when a hard seat insert is used for the heavy duty truck, marine and industrial engines. The result from a hot rodders view is the 906 casting has a little less maximum exhaust flow capacity but it’s not the kind of thing you’d notice without winding the engine out compared to the 062 casting in an engine with substantially more cam, induction and exhaust system than GM provides as stock.

While the 906 casting is a derivative specifically to support valve seat insets many, if not most, simply have induction hardened seats and to a great extent were used by the factory interchangably with the 062 on pickup trucks and vans. Given the machining marks left around the valve seats it takes a pretty sharp eye to even tell the difference of a parent material seat from a pressed insert seat.

I’d say you’re good to go with the 906’s.

As noted, some, but not all 906s have hardened exhaust seats, you have to look to know,......
If there's no hardened exhaust seats, the castings are the same, but for the numbers,....
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