Jim Smart
April 27, 2010

In Marvin's quest for power, he wanted clean airflow beginning at the plenum, transitioning smoothly to ports, bowls, and valves. And this is what he achieved with Edelbrock Glidden/Victor heads and Super Victor induction. Valves and seats must have a clean transition to keep air turbulence minimal. This means a valve seat insert where there's no overhang or ragged edges-pesky zones that disrupt airflow. Valve guides need to be out of the way where there's no turbulence around the stem. This is where good port and bowl work is crucial. Intake manifold gaskets and ports must be right sized where there's no turbulence generated as the air/fuel mixture passes from manifold to cylinder head. By the same token, you want clean exhaust passages where turbulence is kept to a minimum and scavenging is thorough.

Specifics Description
Part Number 61099 (bare)
Combustion Chamber Volume 61cc
Intake Runner Volume 280cc
Exhaust Runner Volume 94cc
Intake Valve Diameter 2.15-inches
Exhaust Valve Diameter 1.56-inches
Valve Stem Diameter 11/32-inch
Valve Type Used Manley hollow stem stainless steel
Valve Guides Manganese bronze
Deck Thickness 5/8-inch
Valve Angle 15-degrees
Exhaust Port Location 2 1/2-inch spread, raised 0.520-inch
Spark Plug Fitment 14mm x 3/4-inch reach with gasket seat

Dyno Pull 1
Holley 4150 (0-80513-1), 1000cfm
0.84/0.84 Jetting
12.54:1 Compression
2-inch x 30-inch x 3 1/2-inch Hooker Headers
36 Degrees BTDC Total Ignition Timing

RPM HP Torque
4,000 399.3 524.3
4,500 467.0 545.1
5,000 513.6 539.5
5,500 541.5 517.1
6,000 551.1 482.5
6,500 541.2 437.3
7,000 522.5 392.0

We learn from this first pull Marvin's expectations were in line with what this engine made in Edelbrock's dyno lab. He predicted 550/550 and got it. Because this is a road race engine, torque is just as important as horsepower. What you don't see on this first pull, which begins at 4,000 rpm, is this engine's broad torque curve. Torque begins to come on strong around 2,500 rpm, peaking at 545.1 lb-ft at 4,500 rpm. Torque hands off to horsepower at 5,500 rpm, which tops out at 551.1 at 6,000 rpm. Most surprising is 551 horsepower at six grand, which means durability. With this engine, you get it all. In road racing and canyon cutting, you want torque to get you out of the corners and horsepower to blast you through the straights.

You may find these numbers disappointing, especially if you're a drag racer, but consider this. Performance is rooted in what we want the engine to do, and we're going to talk about that shortly. If you're building a road race or street engine, you want a nice balance of torque and horsepower. You want a seamless transition from a mid-range torque peak to horsepower as your engine heads into the highlands. Team MCE concluded from this first pull the Holley 4150 needed larger 0.85 jets for the next pull to optimize air/fuel ratio.

"Every engine has its sweet spot," Marvin comments. "We've worked with ignition timing and centered our limit at 36 degrees BTDC." He adds, "We could take it to 38 or 40 degrees BTDC and make more power, but be risking durability." Marvin stresses the difference between a dyno cell and real world conditions. Real world on a racetrack at speed put stresses on an engine we don't see under dyno cell conditions. Keeping timing conservative reduces the possibility of engine damage.

"And here's another tip," Marvin adds, "maximum cylinder pressure occurs within five degrees of top-dead-center (TDC), which means you want the light off to begin at approximately 36 degrees BTDC." "The single greatest power builder is compression ratio," Marvin tells us. "Add compression and you add power." This is the cheapest, fastest way to increase power while keeping octane requirements in mind.

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