ZONES89RS

iTrader: (25)

I just bought a set for 140$, what was it about this casting? I cannot remember what it was, if someone can refresh my memory.

Z

1994Z28Lt1

iTrader: (1)

the thing about the 906's is that some people say because of how the exhaust seat is manufactured/hardened it inhibits mid-lift flow on the 906's vs. the 062's

however there is a lot of conflicting information out there on these heads some say yes some say no

ZONES89RS

iTrader: (25)

Was it the fact it did not have a hardened exhaust seat? I think that might have been it.

slow95z

iTrader: (33)

they have hardened seats, i think the main diff was material thickness as 906s seem to show up in shops more with cracks in them than the 062's.

ZONES89RS

iTrader: (25)

Someone said the exhaust seat is cut different, affecting flow a bit i guess.

jmm98LS1

iTrader: (28)

^^^Correct. I have 906's on my 383, this is the info I found when I was researching this a couple years ago:

The only difference between the 062's and SOME 906's is SOME 906 vortec have a pressed in hardened exhaust seat as oppoesed to a factory flame hardened exhaust seat. The pressed in seat just flows a bit less than the other heads seat. Simple bowl porting (blending) under (deeper) the seat will eliminate any real or perceived difference in flow by eliminating the machined metal "edge" left from the OEM manufacturing process.

I did a little hand blending and fixed them right up.

ZONES89RS

iTrader: (25)

OK, i dont know if i will mess with it, they will be going to the wifes car.

78LT383

The only ones to worry about are the ones from a 305 or from a propane engine. Chances are the ones you have are just fine.

ZONES89RS

iTrader: (25)

They are off a 350 in a 1/2 ton truck.

slow95z

iTrader: (33)

they'll be fine. that truck ran unleaded gas which requires hardened seats.

moge11

its not they are hardened. all valve seats have been hardened since the 70's.
SOME 906's have a single angle valve job on an Iconel valve seat which is EXTREMELY hard.

ZONES89RS

iTrader: (25)

Thanks for the info fellas.

1997bird

iTrader: (2)

They are induction hardened on the intake valve seat & induction hardened or have hardened valve seats on the exhaust side from GM. They will work with either unleaded gas or LPG in either castings.

I rebuild heads for some of the natural gas companies around here and have found that the GM hardened insert exh valve seat heads do not last as long as the regular induction hardened ones. As they tend to crack between the intake & exhaust valve seat on the dry natural gas (they also don't flow as well). These engines are running 24 hrs a day, 365 days a year, for around 5 yrs for us useing the 906 casting with the induction hardened int/exh valve seats. That equates to a little over 1 million hwy miles.

As for the Inconel material, they are harder than a standard induction hardening but are still preaty "soft" compaired to the material we use for the proper LPG conversion. Stellite valves and valve seats are much harder to machine on the valve jobs......