The camshaft is one of the most important parts of an engine when it comes to making power, but it’s also one of the most confusing parts for a beginner. Advertised versus at-.050 duration, lobe separation, intake centerline, lobe lift…it can throw a newcomer into a major case of tireshake. A 300-page book could be written on the individual design characteristics of a cam and its relationship with all the other parts in an engine, but we have only so many pages each month. Some of the cam stories we’ve done in the recent past have gotten rather esoteric, involving custom-ground lobes or combination-specific profiles. That’s great for someone who’s built a few engines, but what about those of you who are just starting to understand how all this works? In the real world, speed shops have the most popular cam grinds in stock, so that’s what most beginning engine builders use.
We decided to hit the dyno and show what the typical, off-the-shelf grinds do for street performance in a common street engine. Of course, the most common street engine is a mildly warmed-over 350 Chevy, a package just like Racing Head Service’s (RHS) High Energy engine. And since RHS is right across the street from Competition Cams, we picked CC’s brains and research records to come up with a selection of its most popular cam grinds.
We tested five camshafts in the same engine to show what each cam does, how much power it makes, where it makes it and why you would want one over the others. The test started with a near-stock cam, the Dual Energy 255 hydraulic, and went up in lift and duration in 10-degree increments until we got to the 286 single-pattern cam. In each test, the only parts changed were the cam and lifters. Every other component, including the valvesprings and ignition timing, stayed the same, and in most cases the carb jetting also remained the same as the baseline. Three runs were made with each camshaft, then this data was averaged. The results show that each cam has its advantages and disadvantages compared to the rest. Which one is for you depends on what you want out of your engine and car.
THE ENGINE
We wanted the test engine to be like the typical street engine. That means streetable compression, no expensive cylinder heads, and no high-dollar, trick parts—just a good, solid performer. RHS’s 350 High Energy small-block Chevy package is just that. The short-block is completely machined, including honing with torque plates, and assembled with a remachined cast crank, remanufactured rods with new bolts, Silv-O-Lite cast pistons, Sealed Power moly rings and Fel-Pro gaskets. The rotating assembly is balanced.
The cylinder heads are World Products Street Replacement (S/R) iron heads with hardened exhaust seats (for unleaded gas) and 1.94/1.50 stainless-steel valves. These heads are a little better than a set of stock heads at making power, but the biggest benefit is that they are very affordable and feature brand-new castings and parts, not rebuilt stuff. Compression comes in at 8.8:1, and there are several different Competition Cams profiles to choose from. Comp Cams’ High Energy hydraulic lifters, pushrods and valvesprings were used throughout our test. The engine comes as a long-block for $1895, but for additional green it can be equipped with an intake, ignition or anything else you want. We specified an Edelbrock Performer intake and a 750-cfm model 3310 Holley four-barrel carburetor, and the dyno headers have 1¾-inch primaries.
TEST 1
The first cam to be tested was the 255 Dual Energy (DE) hydraulic. This cam is similar to a stock grind, with 203 degrees of intake duration and 212 degrees of exhaust duration at .050-lift, intake/exhaust valve lift of .427/.458 and a lobe separation angle of 110 degrees. The Dual Energy cams are dual-pattern, meaning that, in this case, the exhaust has more duration than the intake. A dual-pattern cam is used for several reasons, mostly for increased exhaust scavenging. Since the intake ports typically flow better than the exhaust ports, more exhaust duration means the valve is open longer, compensating for the weaker port flow. Designed for stock-type engines, the 255DE has a very smooth idle and makes most of its power below 5000 rpm, but falls flat on its face after that. This cam made a healthy 389 lbs-ft of torque at only 3000 rpm and 303 horsepower at 5000, but it really nosed over past that, dropping to only 212 at 5500. The vacuum produced at 750 and 1000 rpm was at near-stock levels, illustrating the tame nature of this profile.
TEST 2
The next cam to be tested was the 265DE, which is one step up from the 255. The specs on this cam are 211/221 duration at .050, .442/.465-lift and 110-degree lobe separation angle. This is still considered a mild cam (sometimes called an “RV” cam), but in smaller engines (like a 305 or a 327) it will have a perceptible lope at idle. The idle vacuum is good enough to operate power brakes, and you could run this cam with a stock torque converter without any problems at all. As you can see from the chart, however, it was worth 21 horsepower over the 255 at 5000 rpm, and while the peak torque only increased by 3 lbs-ft, it came 500 rpm higher. Of particular interest is the power made at 5500. Where the 255 was over and done with, the 265 was still making good power.
TEST 3
Jumping ahead another 10 degrees brings us to the 275DE, which pushes the .050-lift duration to 219/229 and the lift to .468/.488, but still with a 110-degree lobe separation angle. This cam has enough duration and lift that you’ll know it’s there. The idle has a good lope to it, but with 14.5 inches of vacuum at 750 rpm, it’s still docile enough for a daily driver. This cam would also work with a stock converter, but because it loses torque down low to make horsepower up high, it works better with a higher-stall converter. With the 275DE, the 350 kept chugging past the point where the other cams fell off, and made 338 peak horsepower at 5500. We made a few pulls to 6000 with this cam to see if it was indeed peaked out, and it was. Horsepower dropped significantly after 5500, but that’s also about the rpm limit of the heads. With bigger heads (or if the S/R’s were ported), this cam would probably peak at 6000.
TEST 4
For this test we ran out of dual-pattern cams, so we went with the next logical choice in a single-pattern cam: the 286H Magnum hydraulic. This cam has 236-degrees duration and .490-lift on both the intake and exhaust, and a 110-degree lobe separation angle. This cam is on the ragged edge of working with power brakes, but in our experience it will produce just enough vacuum to work. The idle is definitely noticeable, to the point where a stock converter will be a bear to live with. A 2500-stall or higher converter is recommended, and the cam will be strangled if the engine doesn’t have an aftermarket intake, headers and a good exhaust. As you can see in the chart, this was almost too much cam for these heads and intake.
While it made three horsepower more than the 275, it peaked at 5000 and dropped by seven horsepower at 5500. Normally, a bigger cam will make more power at higher rpm levels, but the 286 ran up against the restrictive heads and dropped off at 5500. Same with the torque. The 286 made more peak torque and at the same rpm, but lost torque higher up when it should have made more. Again, with better heads it would have kept on pulling hard all the way to 6000.
TEST 5
For the last test, we wanted to see what happens when comparing a hydraulic-lifter cam to a solid of roughly the same specs. We compared the 286 hydraulic to a 282 Magnum solid. Both are single-pattern cams with 236 degrees of duration at .050-lift, and the 282 solid only has an additional .005-inch of lift, at .495. But while this may look like an apples-to-apples comparison, it’s not. Notice that while the .050-lift duration is the same, the advertised duration (282 degrees) of the solid cam is less. Due to the valve lash that is required with a solid lifter, the cam actually ends up being a little smaller (usually comparable to five degrees of duration) than a hydraulic of the same specs. As the dyno chart shows, the solid cam made better power down low and lost power up high, with less peak horsepower. Notice however that the solid cam made more power at 5500 than the hydraulic at the same rpm, but still less peak horsepower and torque. The vacuum levels also show how much tamer the 282S is, with an additional 2.5 inches of vacuum at 750 rpm.
WHICH IS REALLY THE BEST?
While it would seem obvious that the best cam was the 286 hydraulic because it made the most power, that’s not necessarily true. In a car with a stock automatic trans, stock converter and a high rearend gear (such as a 3.08:1 or 2.78:1), this cam would probably be a dog, and the car would probably be quicker with the 275 or 265. And with the stock converter, ya better get used to popping the trans in neutral at every stop, because the engine’s not going to want to idle in gear. The bigger cam is a better choice only if the car is built for it. A good intake and four-barrel, headers, a 2400-stall or higher converter and some more gear in the rear will be required to let this cam really work. Do you want a daily driver or a street racer?
