Can someone tell me the casting differences on SB Vortec heads. I see listing for heads with different casting numbers. Are some more desirable than others? The two I see the most are castings ending with 906 and 062. Which is better or should I be looking for yet a different casting?

Thanks in advance
JM

 

GM part # NAL_12558060, but on the head itself it says 12558062 comes complete, ready to bolt on from summit for 290$ ea., but you have to buy the bolts 60$ more. This is the onesyou want for the generation 1 block. There96 Truck heads..the runner design is from the LT1 Corvette. Go with the 170cc runners if your app is mainly for a street ride. 400+ hp with flat tops. 2 or 4 reliefs..I went with 2 reliefs and very happy with the results. I.224 X230 @ 50. ..LS110 max lift with the springs is .480 but many say no to .480.,..I.477X.480 works for me. Carefull if your going to the bone yard for these heads. This is a bit of a rough idle cam, but no stall converter required. I really like it. Comp cam P# is12-242-2 Grind CS XE268H-10. Would recommend anyting more for street and light strip. Also Preformer or,air gap was my choice on the intake, but hood clearance is a problem with these intakes,but you can go with a drop base breather if you don't want a high rise hood. Drop base for me.

 

As far as CASTING numbers 062 and 906 are the only prouduction ones available.

The 062 is the regular casting most people like to use and is still available from GM new as PART NUMBER 12558060 assembled.

The 906 was used on 1 ton trucks and has hardened exhaust seat inserts installed from the factory. There was a lot of erronous info on the web and in the rags about these having less flow at low-mid lifts than the 062's. This was orginally reported in Chev High Performance about 2-3yrs ago. Well me me being me and having a set of both sitting in the corner of my shop... I just had to see how bad the 906's actually were. Surprise Surprise - I flowed both castings and stock for stock the differences were negliable. Both casting numbers also responded the same to a good 3 angle valve job and then later on to larger valves in my experience. As I understand it Chev High Perf has since recinded that info and now states both casting numbers are good ones.

Either casting number will work well on a street car up to about 450hp with the proper prep work. I do not even bother to try and pick one over the other anymore.

There is also an "over the counter" 206cc intake runner Bowtie Vortec only available from GM Performance parts, but I do not know the casting number right off. I highly doubt you will find a set used thou.
Will

 

if your in need of a performer intake let me know, I have one on my 74 that I'n conerting to fuel injection. I went with the fastburn's when they first came out had to buy the manifold and now I 'm changing. 0 hours I havent even turned it over once.
pic of setup is -------|
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I am building my engine with the 906 casting how much worse than the 062 are these heads?