Even without dyno gains, the Stealth cylinder heads have an advantage simply by being made from lightweight cast aluminum. Better yet, the weight savings is seen at the front of the car, where it matters most. Before bolting the heads on our 440, we ran all three sets of heads across the flow bench at APE. As expected, the mildly-worked factory 915 heads showed the least amount of flow, with the un-ported Stealth heads showing an improvement, and the ported Stealth heads showing the best flow at 323 cfm on the intake side and 271 cfm of exhaust flow.
Mildly ported 915 head flow numbers
Stock 440 Source Stealth head flow numbers
CNC Ported 440 Source Stealth head flow numbers
On the dyno, the results showed exactly what the flow charts showed. By bolting on the “out of the box” Stealth heads and changing nothing else, our 440 street engine picked up power across the board, with peak horsepower climbing to 475 hp, and peak torque to 480 lb-ft. The average numbers of torque and horsepower were also up significantly, a clear indication that the $995 Stealth heads beat our factory 915 castings hands-down. Given that the 915 heads cost us $100 at a swap meet, and then were treated to a valve job, Comp springs, two valve seats, and all new guides, the Stealth heads become a better deal yet. Add stainless steel valves, the labor of port work, surfacing if needed, and the cost of our factory heads quickly not only meets, but exceeds the cost of the Stealth heads.
One area where the factory castings can’t compete at all is the weight of the heads. No matter how much porting and cutting you do to factory heads you can’t reduce their weight by the 40-50 pounds saved by using the aluminum Stealth heads. The other area where factory castings can’t compete is with the flow numbers seen by the CNC ported Stealth heads. It would be nearly impossible to get the same flow from any factory cylinder head that we saw with the CNC ported Stealth heads, and the number of hours it would take to achieve numbers even close to the CNC Stealth’s numbers would make the task cost prohibitive.
440 with 915 heads dyno sheet
440 with stock 440 Source Stealth heads dyno sheet
On the dyno, we had to utilize a different intake with the ported Stealth heads since the intake ports of the heads were taller than the runners of our M-1 intake manifold. To keep our comparison as close as possible, we utilized an Indy Cylinder Head single-plane aluminum intake we had on the shelf. This intake has approximately the same plenum volume as the M-1, with ports more closely matched to the ports of the ported Stealth heads. During our dyno session the CNC ported Stealth heads showed substantially more power than the unported versions on our relatively mild 440, and power numbers climbed to an impressive 532.1 horsepower and 483 lb-ft of torque. On a larger displacement or more race-oriented engine, we’re sure the ported heads would have shown even more sizeable gains.
We learned a lot from out test of 440 Source’s Stealth aluminum cylinder heads, and the results shown in the dyno sheets speak for themselves. Of course there are bigger, more exotic, and more expensive cylinder heads on the market for your big-block Mopar, but if you’re looking for a lightweight, economical upgrade to factory big-block cylinder heads we found 440 Source Stealth aluminum heads to be a great option. Look over our dyno sheets carefully, and we think you’ll agree that for the money, these heads are hard to beat. To see videos of our 440 making dyno pulls, be sure to log onto www.moparmuscle.com.
|440 Source Aluminum Cylinder Heads
|440 Source Aluminum Cylinder Heads CNC Ported
|915 Cast Iron Cylinder Heads
||Cost varies by parts used, repairs and machine work needed, and port work
||Varies by shop (In central Florida: Call APE for a quote)