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Old 08-30-2010, 11:54 AM
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454 L29 Power Upgrade

So I have a mild Gen 6 roller 454, 9:1 CR, .483 lift 224 duration, L29 heads, and headers. I'm guessing it makes anywhere from 380 to 425 hp.

I want to up the power a bit, but do not know which way to go: either a head swap to aluminum ovals or a small roots supercharger like a 174/177. The thing is that if I were to swap heads, I'm worried that the larger valves would hit the pistons. I also want to keep the current mercruiser cam, as I hate camswaps.

So which way should I go? Blower or heads? Would swapping the heads without a cam change yield any additional power? If so, how bout a wild guess at the power? 50 more hp?

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Old 08-30-2010, 12:54 PM
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The cam swap on a roller is as stress free as it gets. If I were you, I'd not hesitate to swap it out, if that's what you decide is needed.

Obviously, better flowing heads will help output. Both Vortec 7400 heads (the '98-'01 12560241 and the '96-'01 10141279) have about 100cc chambers. As you can see HERE, much care has to be used if porting these heads, they have a "peanut port" sized intake port w/a vane cast into the port. They use a "net lash" (non adjustable except for changing the p-rod length), so they need to be changed to an adjustable set up as well.

The Gen 6 has a FT piston, so you'll need to use a head w/a small chamber volume in order to retain the CR w/o a piston swap. In an OEM head, something like the c/n 390 has close to the same chamber size. You need the right gaskets to use Mark IV heads on a Gen 6 block.

Victor Reinz has designed two Nitroseal® head gaskets to specifically allow for this conversion. The installation requires Victor Reinz part number 4918 be installed on the right cylinder bank to maintain proper coolant circulation, and part number 4923 to be installed on the left cylinder bank for the correct coolant flow."
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Old 08-30-2010, 01:52 PM
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The only reason I don't want to do a cam swap is because the fear of developing a an oil pan leak in front after loosening that up take the timing cover off. Due to the flat top pistons, I would go with either closed chamber heads or mill open chambers down.
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