Hot Hemi: Dyno Testing COMP’s Stage 2 HRT Camshaft Kit On A 392 HEMI

Oftentimes, we deal with full-on engine builds that range from mild to wild. But, a ground-up build isn’t always in the cards for a given project. When our own Ivan Korda (a name that should be familiar to the EngineLabs-faithful) came to us with one of his latest projects, he didn’t want to go the full build route, but rather, just a simple camshaft upgrade for a little more pep.

This time, Ivan was firmly out of his comfort zone, with a modern Mopar powerplant as opposed to his usual allegiance to the Blue Oval. So, we immediately reached out to COMP Cams to discuss options, since we knew of their Gen-III HEMI valvetrain research and development work. As luck would have it, they not only had a full selection of cams for the 6.4-liter VVT HEMI engine Ivan had sitting in his garage, but they were in the final stages of development on the lineup of “Master Cam Kits” for that engine.

Under the “HRT” line of camshafts, the COMP Cams master cam kit comes with absolutely everything you need to upgrade and refresh your 2009-and-up VVT HEMI’s valvetrain. That’s the cam, lifters, pushrods, valve springs, spring seats, valve seals, valve locks, and retainers. While some components are necessary for the new camshaft profile — like the springs and phaser limiter — other components are there to ensure that the whole system is in tip-top shape and that your new camshaft will make the most power possible.

Our mill is a low-mile 6.4-liter Gen-III HEMI with VVT. It came from a junkyard and was an awesome score. Our baseline dyno came in a healthy amount above the ratings for a crate 392.

Getting A Baseline

The first step for this project was to take the engine and put it on the engine dyno to get a baseline. The 392 HEMI engine in crate engine form is rated at 485 horsepower and 475 lb-ft of torque. So, considering this is a low-mile salvage-yard pull-out engine, we’d expect the engine to be closer to those numbers than not, but still, a baseline pull or two on the dyno beforehand was in order.

The only variance from stock for the baseline test is that instead of an OEM ECU, the engine was controlled by an Edelbrock Pro-Flo 4+ electronic fuel injection system, and a set of dyno headers. Since the Pro-Flow 4+ is plug-and-play with all of the stock components, it mated right up and required nothing special to be ordered or fabricated.

With the engine loaded up, the throttle was shoved forward and the graph on the screen surprised everyone, as the numbers were significantly higher than the factory rating. After the Pro-Flo 4+ calibrated itself, the numbers were 498.1 horsepower at 5,600 rpm and 526.3 lb-ft of torque at 4,200 rpm, with the pull stopping at 6,500 rpm. That’s 13 horsepower and 51 lb-ft more than the crate 392 is rated at. So, it’s safe to say we started with a good, solid engine.

The Stage 2 HRT Camshaft Master Cam Kit

For our engine, COMP recommended P/N: MK201-304-17. The star of the show, as the part number suggests is the 201-304-17 camshaft. It’s a Stage 2 hydraulic roller HRT camshaft made from billet steel. Designed for the 5.7-liter and 6.4-liter HEMI engines with variable valve timing, the profile has an advertised operating range of 1,900 rpm to 7,000 rpm.

It offers .599 inch of lift on the intake side and .604 inch of lift on the exhaust side. Duration comes in at 222 degrees at .050 inch of lift on the intake and 230 degrees on the exhaust side, with a 115-degree Lobe Separation Angle. Those cam specs not only require aftermarket valve springs, but a cam phaser limiter as well. Both are included in the master kit.

The Phaser Limiter Kit is a patented design that limits the amount of cam phasing possible without eliminating the variable valve timing altogether. The maximum amount of phasing allowed with the kit is 14 degrees (crankshaft, 7 degrees of camshaft movement). This maintains the necessary piston-to-valve clearance required with the larger camshaft.

Here is the complete Cam Master Kit. It comes with the HRT camshaft, valve springs, hydraulic roller lifters, valve spring locators, retainers and locks, pushrods, and a phaser limiter. The rocker studs aren’t part of the kit, but we ordered them as well.

For the valvesprings, the master kit includes a set of beehive springs that were originally designed for high-lift hydraulic roller cams in the LS family, but work exceedingly well in Gen-III HEMI applications as well. The P/N 26918-16 springs are rated at 125 pounds of pressure on the seat, and 367 pounds of open pressure, with a maximum valve lift of .625 inch. The beehive shape of the spring coil is designed to more efficiently handle the harmonics generated at high RPM, while the oval wire is designed to be stronger and dissipate heat better than traditional round-wire springs.

Complimenting the valve springs is a set of COMP’s ID spring locators. These help locate the spring on the valve seat using the inner diameter of the spring as a locator. Keeping the springs in place on the locators is a set of COMP’s 7-degree steel spring retainers designed specifically for Gen-III HEMI applications using beehive valve springs. Designed to hold the higher spring pressures required, the retainers were designed using FEA to optimize the shape for maximum strength at minimum weight. Made from 4140 chromoly steel, the retainers positively locate on the spring’s ID as well.

Securing the retainers are a set of hardened steel 7-degree valve locks. Designed specifically for Gen-III HEMI 8mm triple groove valves, the 7-degree locks offer the same spring location accuracy as COMP’s Super Locks. Then to finish off the valves, a new set of positive-stop PTFE valve seals is included. The high-performance seals are designed for 5/16-inch valves and .500-inch valve guide diameters and they minimize friction while maximizing sealing in a compact form factor to fit under the beehive springs.

Stage 2 HRT Camshaft installation

Our Stage 2 HRT camshaft has some healthy, but still eminently streetable, specs. Lift is .599/.604 and duration at .050 inch is 222-/230-degrees with a 115-degree Lobe Separation Angle.

Lifters And Pushrods

Moving down from the cylinder heads, the Master Cam Kit also includes new hydraulic roller lifters for the Gen-III HEMI engines. They are a non-MDS (Multi-Displacement System; Chrysler’s version of DOD/AFM) design, engineered to be an upgrade over the common “Hellcat” lifter upgrade. They are built with enhanced oiling around the roller axle and bearing for increased longevity and come with four lifter yokes to prevent the lifters from rotating in the lifter bores.

For the pushrods, the kit comes with a set of .080-inch wall-thickness Hi-Tech pushrods designed specifically for Gen-III HEMI applications. The one-piece chromoly tubes are fitted with 5/16-inch ball ends, cryo-treated, and then black oxide finished for strength and durability. The Gen-III HEMI uses a different pushrod length for the intake and exhaust valves, and COMP has spec’d the lengths to provide the optimal amount of preload with the supplied hydraulic lifters.

The bolt-on HEMI-specific valve spring compressor really makes life easy, both on the engine and on the bench. The large windows in the cage make getting locks in and out really easy.

Outside of the Master Cam Kit, we also ordered two other parts for the camshaft swap. The first being a rocker arm stud kit P/N: 4589-KIT. Designed to provide increased clamp load for added stability, a side benefit is that it helps locate the rocker shaft assembly. The 12-point nuts are engineered to be strong and compact for rocker arm clearance, and both the nuts and the studs are made from Grade 12.9 steel.

The second item we ordered was a Gen-III Hemi-specific valve spring compressor tool. It is designed to bolt in place of the rocker arm shaft. The lead screw features a standard hex head while the cage that applies pressure to the valve spring retainer has an open design. This allows for easy access to the valve locks under compression while the cylinder heads are on the engine (as well as with the heads on the bench).

The rocker arm studs replace the traditional metric bolts and come with 12-point low-profile nuts. Both the nuts and studs are Grade 12.9 hardware.

Dyno Testing The New HRT Camshaft

With everything installed and reassembled, it was time to head back to the engine dyno and see how much the new camshaft was worth. After allowing the Pro-Flow 4+ to adjust to the new airflow, it was time to make a full-boogie pull. Right off the bat, the sweep extended another 500 rpm to 7,000 rpm. It was now making power up there thanks to the airflow characteristics and with the advanced lobe design and increased valve spring pressure, control of the valvetrain at the elevated RPM was no problem.

The results you ask? Peak-to-peak increases with the HRT camshaft were 39 horsepower and 10 lb-ft of torque. Peak torque occurred at the same 4,200 rpm as with the stock camshaft, while the horsepower peak increased to 6,400 rpm. It’s worth noting two things. One, the new camshaft profile gained power everywhere in the curve with no losses. Two, the difference in horsepower at 6,500 rpm is significant, at 56 horsepower and 47 lb-ft of torque.

Not a bad gain at all for under two grand in parts on an otherwise stock engine that still retains some variable valve timing. COMP’s “whole system” approach to cam swaps certainly seems to be effective.

Stage 2 HRT Camshaft dyno test

While the peak gains are impressive, if you look at the area under the curve, you really start to get an idea of how much more power this engine is making when it starts to come alive around 4,500 rpm. All from just a simple HRT camshaft upgrade.

Article Sources

More Sources

About the author

Greg Acosta

Greg has spent nineteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
Read My Articles