intake manifolds
You can always send the stocker out to be ported by FaterProms. That's what I did and I like the results. On a stock car it is probably worth 10crank hp and on a modded one probably 15 crank hp. I am just guessing though, could be more...
-Mike
-Mike
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This is the best cost effective option. Of course a LS6 intake would yield better gains, but is looking to be 3x the cost, plus a lot more work.
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so to the OP the best / cheapest i think would be the LS6 swap 
the ported stocker will work fine if you don't plan on swapping your cam/ heads. The largest gains will be from getting an LS6 intake to fit, do a search on LS6 intake in this forum.
TECH Regular
Joined: Nov 2009
Posts: 446
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From: Farmington Hills, MI
The biggest issue with porting is that it doesn't address the closing off of the throttle neck. Just eyeballing it, you lose about 1/3 of your throttle cross-sectional area. I would say that as you bump power, the LS6 (even the LS1) will really start to seperate itself from the ported LS4 manifold. There's no way my cam would keep pulling to 7000 (and beyond if I cared to try) with the stock intake, ported or not.
