Big Block Cylinder Heads - Big-Block Cylinder Head Test

Edelbrock Heads
The Edelbrock Performer RPM oval ports are an interesting mix within the collection of aftermarket aluminum oval-port heads. They offer the largest intake-port volume of 290 cc with the smallest 2.19-inch intake valve. Among the specs we list for each head is the intake port cross-sectional area. We measured each of the five heads in the same basic place in the intake port to determine the smallest cross-sectional area. This dimension, in square inches, is intended to give you an idea of which head will generate the highest intake velocity based on size. A smaller intake-port cross-section will generate a higher intake-flow velocity while larger ports will experience slower velocities. Intake-port velocity (up to a point) has been shown to have a positive effect on cylinder filling, which results in better power. The Edelbrock's intake-flow numbers are decent, although not on a par with the other three aluminum heads, and still performed well despite having the largest intake-port cross-sectional area number.

Edelbrock has always offered excellent castings and competitive flow numbers for a very affordable price. This particular big-block part number comes with steel retainers and springs designed for a flat-tappet cam. To make the test fair, we changed to a set of Comp hydraulic roller springs and titanium retainers. These changes are not reflected in the price of the heads.

Edelbrock has moved the spark plug location toward the center of the cylinder by 0.150 inch. The company says this chamber may need a custom dome piston, but we did not find that necessary on our engine.

Another important consideration is that these heads rely on a stock exhaust-port exit position, which helps with header fitment. As we'll see in the dyno testing, the Edelbrock heads performed well in the horsepower test even though they did not win when evaluated strictly on torque and horsepower. But add in price and suddenly these heads are players, since they are the least expensive of all the aluminum heads we tested. Check out our dollar-per-horsepower evaluation and see if you agree that the Edelbrock heads make excellent fiscal sense.

Edelbrock Performer RPM-O "Roval"
2.19/1.88 valves
110cc chamber
Intake port volume: 290 cc
Stock location exhaust port
Intake cross-section: 3.07 sq. in.
PN 60479

Dart Heads
These are the newest castings amid the oval-port contenders. Clearly Dart was after serious performance since it fitted these 275cc intake ports with 2.25-inch intake valves. Only the TFS heads with 2.30-inch intakes are larger. From a port cross-sectional area standpoint, the Darts are the largest of all the heads we tested, which might have contributed to their overall torque curve performance. One other aspect of these heads that does not show up on the flow numbers is Dart's emphasis on wet-flow development work.

The Dart 275 heads not only have strong intake-port flow numbers, but also offer some of the best exhaust flow numbers in this test. That superior flow can be partially attributed to the 0.300-inch raised exhaust-port exit point.

Dart makes this slick adjustable pushrod guideplate for big-blocks, which we used on all but one of the heads to help align the rocker arm over the valve. The old solution was to cut and weld the guideplates. This is much better.

Dart also raised the exhaust-port exit 0.300 inch, which is a major reason the high-lift exhaust-flow numbers are so strong. What's interesting is that both the Dart and TFS heads offer a 0.300-inch raised exhaust port and that both the Dart and TFS heads' exhaust-port flow numbers make a significant jump at the higher valve lift, virtually duplicating each other as seen on the exhaust-port flow charts.

Dart 275 Oval Port
2.25/1.88 valves
119cc chamber
Intake port volume: 275 cc
Raised exhaust port: 0.300 inch
Intake cross-section: 3.26 sq. in.
PN 19000112