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Discussion Starter · #1 ·
Would any one know of some general flow charts for the Chevrolet Aluminum BBC head (casting number 3946074)?

Acquaintance fell into a set and is comparing these to a set of $3000 AFR's...

I have a good idea of the AFR performances, but OEM Chevy heads...I'm at a loss...

Thanks!

:D
 

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66 El Camino 57 Chevy pickup 2004 Tahoe
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there's really no comparison. Did you use our old friend google to search for previous articles.
 

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Discussion Starter · #3 ·
I realize the AFR's are head and shoulders above the 074 heads, but how decent are these GM aluminum heads?

I did try Google, but I admit to not being a pro 'googler.' Any suggestions...Chevy High Performance didn't test these particular heads...they had a good think going...

Thanks!
 

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Don't have much on those heads. They were used on 69-71 L-88, ZL-1 and also as an RPO option on 454 LS-6 I believe. Does this head have the round exhaust ports? If so, they actually flowed less than the standard square exhaust ports.

Haven't seen any flow numbers, but I can't imagine that they flowed much better on the intake than the equivalent iron rectangular port heads.

If these heads have the holes for the extra head bolts in the two intake runners, they would be the ZL-1 version, and might be worth a few $$ for restoration buffs.

John
 

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I just read an article, may have been on the AFR site or at speedtalk, that compared a set of AFRs to the original Chevy Aluminum castings. I had that exact pair of heads on my motor and sold them and bought the AFRs. FYI, my heads were pristine and I anded up losing a valve seat and messing up one chamber and still got $1000 on Ebay.

To answer your question, The AFRs flowed around 25% better on the intake side, like 30% better or more in the important mid-lift area, and simply destroyed them on the exhaust side (which AFR is known for).

The other issue with the original GM aluminum is the castings are known to be pretty brittle so you are always risking damage in any medium to high-HP usage. If they are clean sell them and buy the AFRs, my 2 cents :)
 
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