We've all read the claims that adding a certain part or widget will add X-amount of horsepower to your engine, but are the claims actually true. Well, yes—and no. It all comes down to application, and no matter how similar two engines might be, the outcome will never be exactly the same.
Let's take for instance, swapping camshafts. Relatively speaking, it's not actually a lot of work to perform to receive what could be the greatest gains in power that an engine can experience. The camshaft is one of the main determining factors in an engine's potential to make power—especially within a given rpm range. Since the affected power band is different depending on camshaft, one of the most important aspects to consider when selecting a camshaft, is to have a realistic, specific rpm goal in mind before you begin. If you are changing the camshaft to get more low-end grunt, choose accordingly. On the other hand, gaining maximum high-rpm horsepower takes an entirely different set of camshaft dimensions. Lying to yourself about what you actually need as opposed to what you actually think you want, has caused many car guys to park their rides and lose interest because the car is no longer enjoyable to drive. We want to help you avoid that particular scenario. To do that, you might need a little information about camshaft specifics, so check out the sidebar.
It's been proven that the 5.7 Hemi responds well to more aggressive cam timing than the factory installed, but just like an old school engine, we wanted to find out if it's possible to over cam an engine—especially when working on a daily driver. To make this swap ideal, we had to make sure that the cam upgrade improved horsepower throughout the entire rev range, not just at the upper limits. While big cams provide a ton of extra power at the top of the rpm range, large cams often sacrifice low and mid-rpm range torque. Since we're discussing street cars, the reality is that the engine spends most of its life between 2,000 and 3,500 rpm, not over 5,000. Occasionally, spirited driving will push that limit, but that only happens occasionally. You need to take that into account when considering a cam swap. Now, there are exceptions to this rule, and it all depends on the desired outcome of the engine, the parameters of the engine build, and other factors. If you're building a modified engine, then it would be best to call the manufacturer and get their recommendations. We're focusing on a completely stock 5.7 Hemi. Although our 5.7 is a crate engine from Mopar, other than a carbureted intake, this engine is the just about the same as thousands of other "as-installed" 5.7 Hemis that were delivered by Chrysler.
We know that a lot of you guys want to boost the power of your ride, but you're just not sure what will work for you. Well, when it comes to increasing the power of a stock 5.7, we figured that we could help you guys choose a camshaft that best suits your needs by testing three different cams from Crane Cams. The camshafts we tested all displayed near stock to what we'll call a mild, muscle car type idle. Our three test cams all raised valve lift of the 5.7's factory .472/.460-inch lift, to .550/.550-inch lift. This lift alone will definitely increase power, but we were curious about what affects, changes in duration would have. Our 5.7 Hemi came with a camshaft that has 196/196-degrees of duration, which definitely enhances a smooth idle quality and higher vacuum. Our Crane cams each came with duration numbers of 210/216, 216/222, and 222/228-degress of duration respectively.
On With the Testing
We first needed to establish a baseline, so we bolted the 5.7 to the Superflow Dyno. It immediately fired, and right away, we noticed its stock-like idle quality. We ran it through a couple of warm up cycles, and decided to turn up the rpm. Everything sounded good until we got to 5,800 rpm. As soon as the tach hit 5,800, the engine began to shake and miss. At the time, we weren't exactly sure whether the stock controller had a rev limiter, or if the stock valve train had reached its limit. Once we made sure that the engine was ok, we made one more pull to see if it happened again—it did. We figured that since we needed to change the valve springs anyway, we would change only the springs, and see if it eliminated our miss. All of the Crane cams used the same PN 99831-16 valvesprings that are good to 600-inch lift, so we only had to do one spring swap.
Once again, the engine missed at 5,800 rpm, and we confirmed the presence of a rev limiter in our engine controller. Unfortunately, we were unable to disable it, and since we were focusing on a true street engine, a 5,700 rpm limit is where we would end our tests. We ran all tests from 3,000 - 5,700 rpm. In stock form, the engine made a very respectable 352 horsepower at 5,300 rpm, and 359 lb-ft of torque at 4,600 rpm. At 3,200 rpm, our torque was 338 lb-ft, and went up from there. The averages in stock form were 293 horsepower and 346 lb-ft of torque at 4,450 rpm.
Crane Cam One (PN 1989501)
As soon as the baseline was out of the way, we installed our first Crane camshaft. We were confident that our increase in lift and duration would boost power, but we were hesitant to guess at how significantly. With .073/.080-inch more lift than the stock cam and 14/20 more degrees of duration, anything was possible. The engine fired immediately, and if going by sound, we weren't sure we even swapped the cam. It idled smoothly, and acted very docile. Our swap was confirmed when we ran our test, as the new camshaft raised our power numbers to 391 horsepower at 5,700 rpm, and torque was up to 375 at 4,500 rpm. The added lift and duration had definitely increased power, but it also moved our average to 306 horsepower and 360 lb-ft of torque.
Now it's time to change the springs. You will need to pressurize the cylinder using an air compressor. The valvespring tool bolts to the shaft stands, and once you have compressed the spring, you can remove the valvespring keepers. Discard the old spring and place the retainer and new spring on the valve. Next, reinstall the keepers. Make sure that to verify that the keepers are flush against the valve, and that the retainer is sitting flat at the top of the valve.
The Crane springs are slightly larger in diameter than the factory pieces, so the damper surrounding the spring will not be used.
After our first pull, we thought we might have a valve train issue, as the engine would miss after 5,700 rpm. To verify whether it was valvetrain or a built-in rev limiter in our engine controller, we changed just the springs and ran it again. The controller has a rev limiter.
Once we had our stock baseline, it was time to try the first of our three Crane camshafts. Our first one was PN 1989501. With .550/.550-inch lift, and duration coming in at 210/216 degrees, we had big hopes.