Chevrolet Inline Six-Cylinder Power Manual, 2nd Edition by Leo Santucci

• Use the inline six's inherent advantages to beat the competition.
• Discover modification secrets known only by a few engine builders.
• Determine the best ways to use supercharging, turbocharging or nitrous oxide.

No matter what engine you are talking about, the cylinder head is the central player in producing horsepower and torque. No other engine component controls so much about the way air gets into and out of the cylinders, and because that is where the horsepower action is, the cylinder head is the key.

Let's not fool ourselves, while Chevy may have given their inline six plenty of good features, the last word in performance-oriented airflow wasn't one of them. As a truck engine, the Chevy six is oriented towards strong low- and mid-range torque, so getting it to whip up a little extra higher-end horsepower takes some effort.

The good news is that your effort can be amply rewarded when teamed with more aggressive camming and carburetion. Should that not be enough, there is always the hybrid head option, which we'll outline in the following chapter.

It is very important to maintain airflow velocity and therefore, those contemplating doing their own modifications should concentrate on excellent valve work. This alone can gain 15-20 CFM. Blending and bowl work, especially to the venturi radius leading to the valve are of critical importance. Do not just cut straight in.

According to Mike Kirby, this is probably the most common mistake he sees on home-ported heads. Look at what the factory did and don’t try to out-guess them.

It is critically important to blend the bowls and short-turn radii down to the valve guides. What we are seeking here is to create a lot of airflow at low to medium valve lifts. We want to maintain a .275” difference between the intake valve size and the bottom of the valve bowl throat.

For example, if we replaced the stock-sized valves on the intakes with 1.94” diameter valves, we want the throat .275” smaller or 1.665”. This differential creates a venturi effect promoting high velocity at the valves and tremendous airflow in the .200” - .500” valve lift area.

Suppose you could add 75-125 HP to your inline at the touch of a button and make no interior changes to your engine? Would that be great or what?

Suppose it were also quite cost-effective to purchase such a system and the installation was very straight-forward? And what if that system didn't make your engine less driveable? Do I have your attention?

Nitrous oxide, or N2O, is not used as a fuel when we apply it to engines; it is just another, more convenient way to increase the oxygen in the fuel/air mixture.

After all, everything we do to increase the power level of these engine revolves around pumping in more fuel and air. Hence, we port and polish, use more radical cam timing, increase the cubic inches and use better flowing carbs and manifolds, etc. Well, N2O contains about 35 percent oxygen, while regular air contains only about 22 percent oxygen. So, doesn't it make sense to use this trick to add power?

• Development history
• Planning your project
• Block identification and selection
• Machining operations
• Oiling system modifications
• Crankshaft and timing gears
• Rods, pistons, and bearings
• Gaskets, sealing, and hardware
• Camshaft design and recommendations
• The cylinder head: key element of a Super Six
• The hybrid cylinder head: a step beyond
• Fuel, exhaust and manifolding
• Ignition: lighting the fire of power
• Supercharging: when enough isn't enough
• Turbocharging: a different route
• What about nitrous oxide
• Aftermarket blocks and heads
• Build sheets
• Resource guide