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Performance Cam Revolution - Valvetrain Advances Give More Power to the People
By Brendan Baker
When selecting a performance camshaft, everything in the engine must be considered because change one thing and something else is affected. One cam supplier said that advances seem to happen daily, so it is important to stay abreast of the latest trends.
The basic function of the camshaft is to open and close the valves in an orderly sequence in between combustion events. However, the amount of variation involved in this most basic function is almost endless. The camshaft is timed in relation to the crankshaft and pistons, and the cam's main objective is to control valve timing so the pistons can pull enough air and fuel into the cylinders to produce maximum torque and horsepower.
In order to understand all the variables that affect the valvetrain, you must first know what you are trying to achieve, say cam experts. If you are a performance engine builder you need to know as much information as possible about the purpose of the engine you're building - whether it's street, drag, circle track or other - to ensure the best cam selection for that application. If you're building a racing engine you will need to ask your customers many questions such as what are your head flow numbers, what size tire you running, what kind of track are racing racing on - dirt or asphalt? These may seem like minor details but, overall, answers to these questions help build a picture for you and your cam supplier, who will then be armed with the knowledge to help you choose the right cam.
For example, let's say you are building a street performance application for a customer, and here again, you should ask your customer, what are you going to do with this? If it's going in a pickup truck and you're towing with it, you're going to want better low-end torque. In this case you may want a cam with more advance ground into it and sacrifice a little on the top-end. Your supplier can help you make the best choice.
There is a wide selection of off-the-shelf cams from several manufacturers and they all, for the most part, break down into stages or levels of performance. So, for instance, a Stage 1 cam would represent the most mild, slightly enhanced stock replacement cam.
"Right now we've got five different cam stages," says Engine Pro's Ron McKey. "We list general characteristics of the cam, whether it's recommended for computer (ECU engines), racing or towing, or whether you need a high stall torque converter and that kind of thing. What we offer right now falls into one of those five stages and it makes it pretty easy to select the right cam."
Not all camshafts are the same, however, and even the various "stages" differ from manufacturer to manufacturer. The following is a general guideline as to the appropriate application for each level of performance.
Stage 1 is a good stock replacement camshaft. These profiles are designed to enhance throttle response and low-end torque while still maintaining adequate fuel efficiency. High vacuum, smooth idle and maximum efficiency are general characteristics of this camshaft selection. These cams are intended for stock or near stock engines and generally don't require upgrades to the rest of the valvetrain.
Stage 2 cam profiles are for applications that require more power in an extended rpm range. These camshafts also work well with stock or mild performance engines and drivetrains and provide good low-end and mid-range power for mild street, off-road and marine use.
Stage 3 cams are typically designed for moderate high performance engines and work well in street/strip or performance marine applications. These profiles have a mild "lump" at idle and offer an extended rpm range with emphasis on a broad mid-range to top end power. Mild cylinder head porting and larger valves will help increase performance with these higher lift, longer duration cams.
Stage 4 cams are designed for very high performance applications and heavily modified engines. They have a definite "lope" at idle and are best suited for street/strip, marine and oval track applications. These grinds tend to have a strong mid-range to top-end torque and horsepower characteristics. Several engine modifications will be necessary to get the maximum benefit from this type of cam.
Stage 5 cams are all out racing cams. These camshafts require extensive engine modifications including bigger valves, lightweight valvetrain, titanium valves, high CFM carburetor or programmable fuel injection, electronic ignition and a performance connecting rod and crankshaft assembly. There are a wide variety of competition cams available and it is up to engine builders to choose the proper cam for his particular application, whether it is drag racing, oval track, road racing or tractor pulling. You will need to have a clear idea of what your customer wants here in order to choose the best profile.
Many of the newer performance engines have roller lifters rather than the conventional flat tappet or solid mechanical lifters. With rollers you can get by with a more aggressive cam profile because of the roller but you have to watch your valve lift, experts say.
"The critical thing is anything over .500? valve lift you have potential for the valve spring to bind," says Clevite Engine Parts' Gary Wertzbar. "Normally you need about .060? clearance on the springs."
Some of the other advantages to a roller lifter cam is that it reduces friction, which generates less heat and wear. A roller cam can also handle a much steeper ramp on the cam profile than a flat tappet cam. This allows the valves to open more quickly and reach maximum lift sooner.
One of the major things you need to look at when you're choosing a cam is to be sure that you have the compatible valvetrain components to go with the cam you choose.
"A lot of the difficulty engine builders have is a customer will say 'I want a real aggressive cam' and not realize what else goes along with that. If you go with durations at .050?, at 224° and above you need to replace springs and go with anti-pump up lifters and so on," says Clevite Engine Parts' Gary Wertzbar.
Liberty Engine Parts' Allan Lafosse says, "We almost never sell a flat tappet cam without selling lifters with it. The only time we do is when the customer stocks lifters already. With the rollers that's different. If it's a mild application we may sell a cam where the engine builder will use the stock lifters, but once the cam gets more aggressive then guys purchase the other components to match the cam. As you get to the bigger, more aggressive cams people are buying a package where you get the cam and the lifters and the spring that's recommended to go with the lifter, and often times they buy the push rods also. But that's usually after they've mocked everything up and checked the lengths."
"We do everything custom," says Mike Jones, Jones Cam Designs. "I use a software program I designed to get the specs I need, but first I must get the necessary information from the engine builder. An engine builder calls me and I ask him parameters of the bore, stroke, rod length, compression ratio, flow numbers on the cylinder head, class they race and what the rules are, and I design the cam for that specific application. If the engine builder wants peak power at 7,200 rpm I make exactly that. I can make the cam for whatever you are trying to do. If you're trying to do something that can't be done I'll tell you that also, says Jones. "If you have a stock set of unported heads and want to turn it 9,000 rpm I'll tell you that won't happen."
Jones machines the cams out of billet or castings depending on what type of application, and he has facilities to make his own billet cams if they're not available for a particular engine.
In 90 percent of applications, roughed in steel billet cams are available. The lobes are already roughed in and pre-heat treated and the bearing journals are finished. All Jones does is grind the profile on the lobes. But in some cases there are no cores because the manufacturer moved the lifter bores, so Jones makes the whole camshaft himself out of billet. That raises the cost so you don't want to do it like this unless you have to, he says.
Selecting a cam that isn't "lumpy" enough may cause some of your customers to complain, however, these cams may not be the best choice for their application and may actually result in a drop off in performance.
"What we run into sometimes is people want a cam that sounds like they spent some money on it," says Engine Pro's McKey. "But at the same time the rest of their car is not really set up to take advantage of that. We've got a couple of cams that have a bit of a noticeable idle. Some people call it quality, some people say it doesn't idle as well, but from what people are looking for in a performance cam they want to hear it but still work fairly well without doing a lot of other modifications. They don't want to machine the head and put bigger springs in. They don't necessarily have headers or a high stall converter either."
When you're dealing with a situation where computer control is an issue many suppliers recommend using cams manufacturers deem computer friendly.
"Most of our economy performance cam grinds are going to be very unfriendly to a computer," says Liberty Engine Parts' Allan Lafosse. "We shy away from the less expensive cams and go straight for the ones that the manufacturer specifically says will work with ECUs. It's mostly the duration that throws off the computer, and when you go for a really big cam the computer starts to get confused. If you get outside of the computer parameters it will trip a code or it won't be able to take advantage of the cam's full potential without being reprogrammed. You've gone beyond just cam selection at that point, now you really need to be thinking of a complete engine package or kit at that point where everything is designed to work together including the computer."
One of the latest developments happening now is some manufacturers and race teams are mechanically balancing camshafts and finding some really big gains. It helps get rid of the harmonics in the valvetrain, according to experts.
"In some applications we've gained 500 or more rpm out of the engine before we ran into valve float just by the balancing the cam alone," says Jones Cam Design's Mike Jones. "We're seeing it as low as 6,000 rpm.
"We developed it first for the Cup teams and it was a small gain for them but it did what we were trying to achieve. I took the idea and started applying it to the smaller racing classes. It's actually a bigger gain for the smaller classes. These guys often times can't use the best parts because of the rules. There are a lot of small circle track classes where they limit you to a stock size spring. And for those applications, balancing the cam is a huge advantage," says Jones.
"In NEXTEL Cup we gained 3 hp and they thought that was great. But when we put it in these lower classes it's even bigger. Because of the extra rpm we're getting out of it, we're able to get another 20 hp by turning it another 400-500 rpm. And I only charge engine builders $99 per cam to do this. It's really taking off now. Everything we've run this balancing setup in we've seen gains.
"There are a lot of things going on that can cause a harmonic. We've seen a valvetrain harmonic due to a crank imbalance, says Jones. We've seen valve float because the guy didn't have a damper on the crank. So balancing anything is going to make significant gains. It seems that by balancing the cam it's helping the life of the timing chain and all the other valvetrain components. They're living longer and we haven't had any breakage. We haven't proven that this is the reason but the results have been very
To keep abreast of what's available in the revolutionary world of camshaft design, you should stay on top of what manufacturers are developing and talk to your suppliers regularly.
For more information on camshaft suppliers and manufacturers, visit the 2006 Engine Builders Buyers Guide available on this Web site.