Hey all, I have a very unique problem. I am building a 350 engine and went to the local junkyard to buy some vortec heads. I found a 1996 chevy tahoe and started taking the heads off. After removal i saw that one head was a 062 casting and one was a 906 casting. I really wanted both to be 062 castings but whatev. My question is, would it be bad to run both castings on my 350 or do I need to swap one of these out (906) for an (062) casting so that they match? I know about the exhaust flow being different on some 906 castings that's why i was wondering. Thanks all.

 

You may find this interesting. It's from the Sallee Chevrolet website.

Quote " Please Note: The casting number myth debunked:
The myth is that there is a difference in the head performance produced by these two castings.
This myth was started by some Magazines that didn't do their homework before publishing their articles.
This is the truth the whole truth and nothing but the truth. So sayith the Grand Wizard GM and his Apprentice Wizard Chevrolet.
10239906 casting has one large single hump.
12558062 casting has 3 small humps.
If either of these two castings have not been altered by GM and the part number changed from 12558060 or altered by someone else (previous owner, etc.), the heads produced by either casting will be identical except for the external cosmetic difference. Both castings are used to make the 12558060 Vortec heads which are the true unaltered Vortec heads.
Heads from both castings come out of their cast IDENTICAL except for the minor cosmetic external differences!!!!!!!! " Unquote.

Judge for yourself.

 

Some Vortec heads are machined differently in the exhaust throat area. This was for heavier-duty applications. If that engine started with a matched pair, and it probably did, then odds are someone experienced "the Vortec crack" and just replaced it with whatever was available right then at a fair price. Either one could be the replacement. You need to remove the valves and check. If they look the same, they'll perform the same. If you have one of the HD exhaust throats, then the only fix is larger 1.60" exhaust valves ( minimum ) and some machine shop work.

 

Great! thanks for the good info all!