5.7L Hemi Cam Swap Adds 67 Horsepower
Make 434hp and 440 lb-ft with this cam, springs, and headers
In part 1, we took a cast aside and forgotten junkyard 5.7L truck Hemi engine that was in such disarray that we no longer knew if it ran. In fact, we can't remember where it came from other than some online junkyard dismantler. The biggest question hovering over the Hemi was why were there so many pieces missing? Most of the big stuff was there, like the short-block and cylinder heads, but it was far from being in running condition. The missing parts list included things like a rocker set, valve covers, and oil pan. Also absent was the induction system, front cover, and sensor package (cam and crank).
Just Add Nitrous
Despite the fact that we could nearly pick up a complete used Hemi for the price of these missing components (maybe why it sat for so long), we decided to solve the mystery and get it running back. Not content to merely have a running Hemi, we also added a little NX nitrous kit to up the power from 367 hp and 414 lb-ft to 495 hp and 530 lb-ft. With part 1 completed, we now turn our attention to increasing the naturally aspirated power output.
Hemi owners, even of the early version like our 2006, have one heck of a starting point. Much like LS owners, the Hemi responds very well to aggressive cam timing. The reason for the responsiveness is that the Hemi is blessed with basically everything else needed to make big power (especially the later "Eagle" and "Apache" versions. Learn the differences here). Having free-flowing heads certainly helps the situation, but the intake plays a big part as well. Even the lowly truck intakes (again like the LS) can support exceptional power, while maintaining impressive torque production, thanks to their generous runner length. (A dyno test of intake manifolds for the 5.7L Hemi can be found here.)
With ample displacement and compression, the only thing stopping a Hemi from making power is the mild factory cam timing, especially on the Ram trucks. The mystery surrounding our Hemi wasn't so much whether the cam swap increase the power output, but by how much? It should be pointed out that we were treading lightly with this junkyard engine, as these early Hemis were notorious for dropping valve seats. For most owners, it isn't a matter of if, but when, and having a mystery motor only made things worse. Were we living on borrowed time? Would the whole thing explode in a fiery ball of piston parts? All we knew was that repairing the stock heads was out of the question (meaning budget), so we continued with our cam swap and hoped for the best.
A Camshaft for the Hemi
Having run the baseline already with our nitrous test, we tore into the Hemi to replace the cam. Off came the coil packs, valve covers, and rockers to allow for swapping out the stock springs. The new Comp HRT cam profile we decided to run (.596/.582-inch lift, a 220/230-degree duration split, and 113-degree LSA) required a valve spring upgrade, so we installed a set of Comp 7228-16 springs. Comp offers no less than three different spring packages for the various Hemi generations, allowing users to select spring kits based on their intended cam lift. Comp Cams also introduced a spring compressor tool for the Hemi at SEMA, but it was not available in time for our test.
Installing Higher-Lift Springs
Undaunted, we pulled the heads to replace the springs using a conventional compressor on hand at Westech Performance. Once the spring swap was complete, we continued with the installation of the new cam. Off came the front cover, timing gear, and cam retaining plate to provide access to the stock Ram cam. We made sure to liberally coat the new Comp cam before the swap and had everything back together in no time. The cam swap was easy on the engine dyno, but we look forward to having the spring compressor tool to allow us to perform the spring swap without head removal.
5.7L Hemi Dyno Test: Stock vs Comp Cam
After installing the new cam, we were excited about the power potential. You'll remember that our 5.7L produced peak numbers of 367 hp and 414 lb-ft of torque in stock trim with Hooker long-tube headers and our stock throttle body that we had rigged and hacked to be manually operated via cable. The 5.7L Ram motor was plenty torquey, but we wanted to see this thing start to pull a little harder on the big end. The cam was just what the doctored ordered, as our engine thumped out an additional 67 hp with the cam swap. Equipped with the new HRT cam, the 5.7L produced 434 hp and 440 lb-ft of torque.
We suspect the Hemi was down slightly on power from where the old dog should be (both with the stock cam and the new Comp version), but we sure liked the gains offered by the HRT cam. It's hard to argue with an extra 67 hp, especially when the big gains on the top came with no penalty in power down low. Cam swaps can be tricky, as extra top-end power is often accompanied by a loss in low-speed torque, but it looks like the boys at Comp did their homework on the new HRT design. What's next for the this Hemi? It looks like his shopping cart is clattering ever closer with headers, intakes, and boost!
Much like GM's LS platform, the Dodge Hemi was blessed with ample displacement, head flow, and a solid induction system. The only thing missing from the performance equation on a Hemi is cam timing. This test is a perfect example of what happens when you add a cam to an engine that needs only cam timing. Run with the stock cam, the 5.7L Hemi produced 367 hp and 414 lb-ft of torque. After installation of the new HRT cam from Comp Cams, the power output jumped to 434 hp and 440 lb-ft of torque. The cam swap netted an impressive gain of 67 hp!