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Nasty Nailhead

New Technology Invades

John Gunnell - April 02, 2014 04:50 PM

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The high-tech Nailhead is attached to a Tremec six-speed automatic

John Gunnell
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A lot of thought went into both the look and the technology of the Nailhead.

John Gunnell

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Guy Henson built a Buick “nailhead” V-8 for a high-tech hot rod. “We wanted to build a Buick Nailhead pump motor that a hot rodder could get in, pull up to a pump and drive away.”
The initial thought was to use an available dual four-barrel or tri-power intake manifold, but things started getting a bit radical when Henson suggested adding a Whipple supercharger.
Henson carved a billet intake out of aluminum, put the Whipple on top of it, added a custom-built plenum and topped the package off with eight Hillborn throttle bodies carrying individual spun aluminum velocity stacks and filters. He extended the supercharger four inches to get the belt alignment right. He carved a water pump pulley out of billet and put a crank sensor on it. The customer wanted Hillborn throttle bodies and stacks, so Guy mocked up a plenum in wood and carved out half of it on his own milling machine.
The intake system allows the throttle bodies to be positioned straight out or tipped at up to a 30-degree angle. Guy added an elbow on back of the plenum to hide an IAC (Idle Air Control) motor that allows him to control the throttle blades and completely close them if he wants.
For engine management, Guy used a FAST system. The injectors that feed the Nailhead are hidden between the custom intake and the finned polished aluminum lifter cover. Guy ran a vacuum line so the owner can operate vacuum-operated accessories. Dress-up items include finned polished aluminum Offenhauser rocker covers and steel headers sourced from a Speedway Motors.
Guy devised different ways to run his linkages. On the Nailhead, he ran a cogged belt drive off the front of the plenum with belt tensioners. He’s pulling the throttle in the back through the center of the plenum. He incorporated adjustable return springs below the throttle bodies on both sides. The 2.3-liter Whipple came off a kit for a 6.0-liter Chevy truck engine. Whipple has since changed the design to make it suitable for late-model muscle cars. However, the bolt pattern on the back is the same
The Nailhead has huge 125cc chambers and Guy feels that with 400+ cubic inches (this particular engine has 413 cubes), you’re filling up such a large volume of space that the compression ratio can go up too high.

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