How essential is it to match a cam with heads?
03-19-2006, 07:51 PM
#1
How essential is it to match a cam with heads? I was wondering because I was going forced induction route and had a cam speced out to best match a blower, but also i would like to know just how good you could just slap a set of heads on and what kind of results i would get. mods are in the sig and the specs on the cam are 214/220 .561/.581 116 LSA thanks!
03-19-2006, 07:56 PM
#2
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From what I've read and learned it's very important. Probably more important when staying N/A but still needs to be thought out when going FI. But a not so well matched combo may not have such a large impact since it isnt your major power adder. The heads should compliment the cam which should compliment your turbo/supercharger. It should be thought out as one major component instead of 3 individual items. I know someone will chime in with much more specific advice.
03-19-2006, 08:28 PM
#3
It all depends on what heads they are. Most any set of aftermarket heads will net you at least something as they are better than stock.
Think of it this way - anyone can stick a .630 lift cam in their stock engine and it will make more power than stock (longer duration and higher lift equal more fuel and air and more power). But, the stock heads/induction system are going to restrict it. With this cam in mind, one would pick a set of heads with peak flow as close to the max lift of the cam (.630) to utilize the cam's dimensions for optimal power from the heads added. Then you have to think, well ok, these heads flow x at y lift, but how in the hell are they going to get that much are flow that with my current intake/tb (or FI setup)? If those are restricting it, then you've got another thing to think about.
The point is that anything aftermarket is an upgrade from stock, but it won't always net you the gains you are looking for if your components are mismatched. It would be too easy if x set of heads gained y hp/tq for every car, but that ain't the name of the game. Some people look for big gains from their heads N/A while some only look for mediocrity as they have other power adders to pick up any slack, such as yourself. All of these components work together (and differently on different cars) to utilize each component's strong point(s), and with a lot of brain power and luck you get what you're looking for.
Think of it this way - anyone can stick a .630 lift cam in their stock engine and it will make more power than stock (longer duration and higher lift equal more fuel and air and more power). But, the stock heads/induction system are going to restrict it. With this cam in mind, one would pick a set of heads with peak flow as close to the max lift of the cam (.630) to utilize the cam's dimensions for optimal power from the heads added. Then you have to think, well ok, these heads flow x at y lift, but how in the hell are they going to get that much are flow that with my current intake/tb (or FI setup)? If those are restricting it, then you've got another thing to think about.
The point is that anything aftermarket is an upgrade from stock, but it won't always net you the gains you are looking for if your components are mismatched. It would be too easy if x set of heads gained y hp/tq for every car, but that ain't the name of the game. Some people look for big gains from their heads N/A while some only look for mediocrity as they have other power adders to pick up any slack, such as yourself. All of these components work together (and differently on different cars) to utilize each component's strong point(s), and with a lot of brain power and luck you get what you're looking for.
03-19-2006, 10:55 PM
#4
Flow is one thing... matching the compression to the cam is a much bigger story. If you have really nice flowing heads, a big cam, and low dynamic compression, you'll have a dog off the line that doesn't make any torque. An optimum dynamic compression ratio (DCR) will net you much better drivability and power. Why? Cylinder pressure = torque. The more force the combusion process produces on the piston, the harder it is shoved down the cylinder, thus twisting the crank harder to produce more torque.
Of course, you'll need optimum cam events more that "matched" heads. For head selection, go with something that will net a good CFM without hogged out ports. Such designs make nice peak power, but part throttle and low RPM cruising is worse than stock, because those heads have terrible low speed flow (velocity is not kept up). Therefore, getting heads that effectively add airflow to the air/fuel mix of the combustion process is more important.
Of course, you'll need optimum cam events more that "matched" heads. For head selection, go with something that will net a good CFM without hogged out ports. Such designs make nice peak power, but part throttle and low RPM cruising is worse than stock, because those heads have terrible low speed flow (velocity is not kept up). Therefore, getting heads that effectively add airflow to the air/fuel mix of the combustion process is more important.
