The modern Hemi is an impressive piece of engineering. One need only look at the previous generation 5.9 Magnum engine as a comparison to see that Dodge made a massive evolutionary step forward when they introduced the Hemi. Who among us didn't like the fact that the Hemi offered 100 extra horsepower over the outgoing Magnum 360? A big factor is that the Hemi was blessed with (relatively) massive head-flow. It seems that the engineers stumbled across the notion that you can get big power by combining mild cam-timing with high-flow cylinder heads. Thanks to the impressive cylinder heads, the Hemi has a reputation for responding very well to cam changes, but what happens after the cam swap? The question we were looking to answer is this; given the impressive head flow in stock configuration, is there power to be had from further improving head flow? In short, what kind of power gains are available from ported Hemi heads?
Testing ported Hemi heads is easy enough, but we decided to go one better. The problem (or limitation) of testing a set of ported heads against a set of stock (as cast) heads, is that the results are combination dependent. If someone were to ask if ported heads are worthwhile, and test them on our mild 5.7, their opinion might be very different than had they run the test on our 6.1 stroker. More than likely, your Hemi engine combination is holding back the power potential of your heads, rather than the other way around. Is it possible for ported heads to offer just 10-12 horsepower on a mild 5.7, and over 40 horsepower on a larger, more powerful engine? The only way to illustrate this point was to perform back-to-back head tests on two different Hemi engines, starting with a mild, 2004 5.7, equipped with little more than a Comp Cam upgrade.
Test 1: Stock vs. TEA-Ported 5.7 Heads on a Mild 5.7
Test Number One involved a 2004 5.7 Hemi, pulled from the engine bay of a Dodge Ram 1500 pickup. The only modification to the Hemi was the addition of a mild Comp camshaft. The 260H-13 (PN: 112-500-11) cam offered a .522/.525-inch lift split, a 208/212 duration split at .050 inch, and a 113-degree lobe separation angle. There were a few smaller cams available in the Tri-Power Xtreme series, but this 260H-13 camshaft was the smallest offering in Comp's XFI series. To put these numbers into perspective, the stock Hemi cam offers just .470-inch lift, 196 degrees of duration, and shared the 113-degree LSA. The engine was run with SRT8 exhaust manifolds, and tuned with the Fast XFI/XIM management system. Equipped with the stock 5.7 heads, the cam-only upgraded 5.7 produced peak numbers of 401 horsepower at 5,600 rpm, and 427 lb-ft of torque at 4,500 rpm. Torque production exceeded 400 lb-ft from 3,600 rpm to 5,200 rpm. Now it was time for the ported heads.
Dodge now offers four different Hemi heads, the early 5.7 (like the ones we tested), the 6.1, the later 5.7 Eagle, and the 6.4 Apache heads. The early 5.7 heads we tested, offered the lowest stock flow-rates of the bunch, topping out at 269 cfm at .700-inch lift. All of the later heads offer significantly more flow in as-cast form, with each easily exceeding 300 cfm. Flow numbers for the 6.4 Apache heads are said to reach 340 cfm, a big number even for ported 5.7 heads, as our ported early castings from Total Engine Airflow (TEA) checked in at 329 cfm. The improvement in airflow offered by the porting from TEA was significant, as the ported heads flow enough to support over 650 horsepower. The question now was; would the mild engine be able to take advantage of the extra head flow when it was making only 400 horsepower? The answer was not really, as the stock heads were already sufficient to support the current power level. The ported heads improved the power output slightly, to 413 horsepower at 5,700 rpm, and 439 lb-ft of torque at 4,600 rpm, but it was another case of the mild combination holding the heads back. The results would change in test two.
|TEST 1 POWER NUMBERS
|Hemi Head Test—2004 5.7L Hemi (260 Comp Cam)
|Stock Heads—401 hp at 5,600 rpm, 427 lb-ft at 4,500 rpm
|Ported heads—413 hp at 5,700 rpm, 439 lb-ft at 4,600 rpm
1. Test mule number one came fresh from a local wrecking yard. The 5.7 was pulled from a 2004 Dodge Ram 1500. The motor had logged 135,000, but was still in remarkable shape internally.
2. The only internal upgrade to the truck 5.7 was to replace the truck cam with a mild Comp grind. The 260H-13 offered a .522/.525-inch lift split, a 208/212 duration split at .050-inch, and a 113-degree lobe separation angle.
3. Run with the mild Comp cam, stock 5.7 heads and truck intake, the 5.7 produced 401 horsepower at 5,600 rpm, and 427 lb-ft of torque at 4,500 rpm.
4. The stock heads were removed to make way for a set of ported 5.7 heads from Total Engine Airflow. The ported heads from TEA increased the intake flow from 269 cfm to 329 cfm, a gain of 60 cfm at .700 lift. Gains in exhaust flow were equally impressive, as the porting increase flow from 186 cfm to 249 cfm.