Do Big Intake Runners Kill Bottom-End Torque? The ‘Engine Masters’ Investigate

(Image/Hot Rod)

The Motor Trend show Engine Masters is all about finding out what makes horsepower and what doesn’t.

Hosts David Freiburger and Steve Dulcich have tested everything from headers and carburetors to camshafts, superchargers, mufflers, and air cleaners.

In Engine Masters Episode 28, they set out to learn whether cylinder heads with big intake runners really kill bottom-end torque.

Freiburger and Dulcich used a BluePrint Engines Ford 408-cubic-inch, 425-horsepower long block crate engine as the guinea pig for their test.

They swapped the cam out for a COMP Cams Xtreme Energy retrofit roller cam with .513 inches of valve lift and 218°/224° duration @.050 inch lift. Up top is an Edelbrock Performer RPM Air-Gap dual plane intake manifold with an 850 cfm Holley Ultra XP carburetor.

Spark is provided by an MSD Ford Crate Engine ignition kit, and Hooker provided a pair of full-length Super Competition headers with 1¾-inch primaries.

Three Air Flow Research Renegade cylinder heads were tested, all with 58cc combustion chambers:

1. 20-Degree Street Renegade – 165cc intake runners and 1.290-inch valve springs rated up to .600-inch valve lift.
2. Renegade Competition – 195cc intake runners and 1.290-inch valve springs rated up to .600-inch valve lift.
3. Renegade Race – 205cc intake runners and 1.600-inch valve springs rated to .710-inch valve lift.

The Results

So did Freiburger and Dulcich dispel the Big Ports = No Torque theory, or did they stumble on an awesome combo?

The answer to at least one of those questions is: Yes.

But you’ll have to watch the episode to find out.

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Engine Parts List

Here are the parts Freiburger and Dulcich used:

• BluePrint Engines Ford 408 C.I.D./425HP Long Block Crate Engine
• COMP Cams Xtreme Energy Retrofit Roller Camshaft
• Edelbrock Performer RPM Air-Gap Intake Manifold
• Holley Ultra XP Carburetor, 850 cfm
• MSD Ford Crate Engine Ignition Kit
• Hooker Super Competition Headers

Cylinder Heads

And here are the three cylinder heads from the test:

• Air Flow Research 165cc Street Cylinder Heads, Pair
• Air Flow Research 195cc Renegade Competition Cylinder Heads, Pair
• Air Flow Research 205cc Renegade Race Cylinder Heads, Pair