Learn about roller and flat-tappet camshafts. Learn about the differences between drag racing and towing applications for choosing the best camshaft for your vehicle. Better understand the duration and lift numbers for your ride. Hear why a mild camshaft is most likely the right choice for you. All by watching this Summit Racing Quick Flicks video.
Also, check out our earlier post to learn the basics of camshaft specifications.
…today we’re going to talk about the differences between mild camshafts and aggressive camshafts and which is right for your application.
So it’s time to call Summit and ask for some advice on which camshaft is going to work best for your vehicle application. You may come to find that we are probably going to ask quite a few more questions than you would expect. Mainly, we are going to start with the type of engine, of course, and we are going to start asking you specifics about that engine–what the compression ratio is…what type of cylinder head you may be using…type of intake manifold that is on the engine…carburetion…does that vehicle’s engine have headers. We may ask you about your rear gearing, your tire size, torque converter stall, if you have an automatic transmission, and the type of vehicle the engine is actually in. The reason for this is all of these are going to come together to help us make a selection of a camshaft that is best for your complete application and not just what camshaft is going to make the most horsepower.
The reality is peak horsepower numbers really don’t translate into max. vehicle performance. What we are looking for is to place a camshaft in your engine that is going to make the best overall horsepower, meaning from beginning to end in the power band. We can select a camshaft for you that is real peaky as far as its going to make max. horsepower at 6500 RPM. But is that really usable horsepower in your application? Is that the type of driving you are doing with that vehicle? A lot of times we come to find that customers are interested in camshafts that are going to make their vehicle to perform best but unrealistically they are going to expect it to take a really large camshaft for that application.
Once you have supplied us all the information that is requested from you, we are going to go ahead and take an evaluation of that information, and we are going to look at a lot of things as far as cam profiles go and what is available for your engine combination. You are going to find there is going to be a wide range of camshafts available between camshaft styles far as flat tappets compared to rollers and as far as duration numbers and lift numbers, and all of these are going to play into our decision. In most cases, we are going to go ahead and try to stick with whatever you had in the engine to begin with as far as cam style goes, whether you had a flat tappet or roller because this will be the easiest transition to the new camshaft. Meaning this won’t cost you a lot of money to change things like pushrod length and lifter designs, and we may even be able to get away with the stock type valve spring instead of upgrading to a larger valve spring, in which case now we have to go ahead and machine the spring pockets in the head to accept the larger valve spring. Once we’ve taken that complete evaluation, we are going to take a look at the driving as well. We are going to look at how the vehicle is mainly going to be used because an engine can necessitate or accept an extremely large camshaft and will perform with it, but it doesn’t necessarily mean that it’s going to make the type of horsepower that’s going to perform properly in the type of vehicle that you’re putting it in and the way you are planning on driving the vehicle. The camshaft I am going to select for a drag race vehicle is going to be completely different than a camshaft I am going to select for maybe a road race car or if we look at a street strip application in comparison to a towing application. What you are going to come to from one another as far as idle quality goes, engine vacuum characteristics, and requirements when it comes to the torque converter that is going to be necessary to support that type of camshaft as well.
What you will come to find in most cases is that a mild camshaft is the right choice for your engine, especially if it’s a vehicle that is driven regularly. You’re going to experience much better driving in the end with the mild camshaft over the extremely large camshaft, which will sound great and it will grab a lot of attention but it is going to be harder on valvetrain parts, is going to require much more maintenance, and cause the drivability of that vehicle to go down as an end result. If you want to go ahead and check out cam profiles that will fit your application best, let’s get into the numbers a little bit in what they actually mean and what you should be looking for.
Like we mentioned, the application is the key to all of this and let’s say we have a towing application and we are looking for a camshaft for that specific vehicle type, what you are going to be looking for are some specific duration numbers and some lobe separation numbers. I will tell you that lift numbers kind of a lie. Meaning that a camshaft can have a lot of lift or a little lift, but it really is dependent on the engine type when it comes to lift numbers and what performs best in that style of engine, so we kind of stay away from really focusing on lift numbers and we look more at the duration and lobe separation numbers and what’s going to work.
For a towing application, we would be looking at duration at fifty numbers probably somewhere in the range of 210-215 and a lobe separation that is a little higher–somewhere between 112 to 114. That style of camshaft is going to very smooth idle quality but it is going to make a lot of low-end torque and it is going to respond really well–as soon as you hit that gas pedal without a lot of changes on top of it all. This type of camshaft is not going to require a stall converter or a ton of compression or a high-rise intake or anything of that nature to perform like it’s supposed to and it’s not going to be a very peaky camshaft . It’s going to have a broad power band way down low in the rpm band.
If you were looking for a street camshaft–or a mild camshaft as we would call it–now we are probably going to be looking for a camshaft with duration numbers at fifty around that 215 to 225 range–even up to 230. Actually, I’ve seen them go as high as that with a lobe separation between 110 to 114, depending on the cam profile as well as depending on if maybe we had a power adder like nitrous or a supercharger or something like that. In this application, gearing becomes a little more important as well. You don’t want to go ahead and have a 230 duration camshaft with a 2.73 gear (because) you know the car is not going to want to accelerate properly at that point. It’s going to want to make the torque converter a little funny as well if we have an automatic transmission, so we kind of want to pay attention to those little aspects.
Then you get into race profile. Race profiles can range all over the place, depending on the type of racing that is being done. I have seen race cams at 225 duration at 50 all the way up to 270, 280 durations at 50, depending on the type of racing that is being done and where we expect that engine to make power with that specific racing. The lobe separation follows suit as well as you can go to a 106 to a 114 duration, depending on the type of racing that you are doing and how you want that vehicle to respond when you hit that gas pedal. Now remember, as you start getting lower in those lobe separations numbers, the vacuum goes away completely. So if you have power brakes, a transmission that has a vacuum modulator, or worst case scenario, something like a 76 Corvette where every single thing is vacuum operation on that vehicle, you put a 106-108 lobe separation camshaft on that car, it will sound great but nothing’s going to work on it. Your headlight doorsaren’t going to open, your heater controls may stop working–everything kind of goes to the wayside. So remember, you have to look at the complete combination as a whole in the end to really choose the proper the camshaft for you vehicle.
Before you make the final decision on what camshaft you want to go with, there is one last thing to consider and that is the lack of zinc in today’s oil. This lack of zinc is creating a lot of problems for flat tappet camshafts, meaning the oil is not really bonding to the part, especially when the camshaft is one of the last things to get oiled in the engine. We are getting a lot of lifter and lobe wear issues because of this. If you are going to go with a hydraulic flat tappet camshaft–or any flat tappet camshaft for that matter–make sure that you place a zinc additive in with every oil change. This will go ahead and give the oil the proper bonding property so that you don’t have excessive cam wear throughout that hydraulic flat tappet camshaft’s life.
With all of the variables involved in selecting the proper camshaft for your vehicle, remember we do highly suggest that you contact our tech department at 330-630-0240 so you can get some good advice on which camshaft is right for your application. And remember, like many things in life, bigger is not always better.