How to choose the right cam??

[74scamp360]

Hey, i've always wondered how some of you guys can recommend what cam to use in certain applications depending on the specs. Now me on the other hand, i see those numbers whether they be duration or lift or whatever and have no idea what to make of them. So what i'm asking of you guys is how to figure out what cams you should be using and how to be able to look at those numbers and figure out what they mean to me. Thanks in advance, i'm a young guy and still learning some of the finer details.

 

[1wild&crazyguy]

The further past 219*@.050 you go, the more gear & stall[if AT] you need.

Or the further past 260* advertised, the more gear & stall [if AT] you need.

It's all about a shift of torque/power higher up in the rpm range which equates to hp rpm x torque=HP.

What kind of power are you looking for?
How much do you want to rev it?
How much gear are you comfortable with running on the freeway?
How deep are your pockets?

 

[Max340]

The key to cam selection is to understand that force is made from cylinder pressure. Longer duration cams will "bleed" off the pressure, so higher compression ratios are needed to make up the difference. Also, a longer duration cam will make horsepower at higher RPM, at the sacrifice of torque on the low end. A shorter duration will make better torque, but top end horsepower will drop off.

So a low compression ratio will do better with a shorter duration cam, while a high CR and a short duration may be too much pressure and cause problems. Conversely, a long duration and low CR will make even less power than a stock cam.

Lift is another factor. Lift increases air flow, and does little else to the power profile. In a comparison of two identical cams except for lift, the higher lift will gain power over the other, but not a huge amount.

If you want to gain a better idea of how all the numbers work together, get a dyno program for your PC, and push the numbers around. Many will claim the results are not accurate to the real world. This may be so, BUT, it will give you a hands on, easily modified method of seeing how the numbers react to the changes you make.

 

[crackedback]

Comp Cams has a tutorial about camshafts, specs and how they effect end use.

At least they used to

 

[74scamp360]

Thanks guys that helps a bit.
Crackedback, that's what i thought but i took a look around their site and didn't really see what i was after. All they seem to have is a form that you can fill out and send to them to let you know what their reccomendations are. I'd just like to know how to make sense of it all right now. Thanks again guys, anyone else??

 

[godfatherofchry]

wen I buy a cam I call the cam co.I have a self full of cams that are supposed to be good.and I'm Shir they are but not for what I was putting together at the time.after trying this then try another then call the cam co.and wonder why did I spend all that money wen one call did what I wanted to start with.they will want to know everything about what your putting together.that's my thuat on cams.

 

[74scamp360]

ya good point, i just want to have an idea of what it all means you know, thanks for the tip and i think that's a great idea calling the companies

 

[Prine]

I would tell you how I select a camshaft, but this is one of those questions that is loaded....in the end it boils down to sacrifice for harmony.

You set a ideal hp/tq goal.
You define the purpose of the engine, and how high you want to spin it.
You define the necessary compression ratio to attain that goal.
You define how much airflow is required to achieve the goal.

THEN.....You pick a cam that fits your profile.

Engines are Air Compressors....the cam just controls when and how long the valves are open in syncrinization with the crankshaft.

I personally like the mild 264/272 advertised duration.....220/230* @ .050 cams....good vacuum, good jump in power 6000-6500 capabililty.

Everybodys goals and budgets are different.

 

[crackedback]

If you are serious about buying a cam for all out perfornmance, call someone that will cut one from the master lobe catalog, like Brian at Indio Motor. You have to be honest about what you want to do, but, most will nail it pretty good. IMO, most people put way too much duration in their stuff.

For a basic street build, most cam companies have a cam that would work off the shelf.

 

[rumblefish360]

If you are serious about buying a cam for all out perfornmance, call someone that will cut one from the master lobe catalog, like Brian at Indio Motor. You have to be honest about what you want to do, but, most will nail it pretty good. IMO, most people put way too much duration in their stuff.

For a basic street build, most cam companies have a cam that would work off the shelf.

Excellent reply and many others up top as well.

Talking to a known company like Comp is great. However, there will be a problem if you decide to talk to them over and over again and then another place. Everyone has there own ideas. That's why you see use guys allway throwing out different numbers all the time to what seems like the same or very similar combo.

Now try these instructions for your own pick. And then run it past us for a basic critic/bench racing talk. We'll keep you from catostophic mistakes.

Based on what you want your car to do, we'll assume it's for a high performance application. And that you have a basic idea of what that is and the set up that will be on the car.

Look at the cam catolog and note that the cams have a RPM range they operate in. Based on that, you should be able to select a cam in the RPM range you'll be "Performing" in. Not cruising in. And it should work with your gear ratio.

Know your heads and there state that there in. Where the air flow stop or stalls. IMO, I try and use as much cam as the port will flow.

Centerline of cams. As a basic outline, a normal performance cam will be on a 110. A 112 C-line has a melloer idle and a 114 is stock for many cars. Going further down, like a 108 will induce more choppyness to the idle. A 106 is a radical idle difficult to tune at idle. 104 is madness for 90% of street cars.

Now go hunt for fun and come back with a "What do you think" choice.
Of course, tell us about the cars goals and what equipment it'll end up with. Rear gear ratio, tranny, auto/manual, cars weight and engine size with it's compresion and what head you have in what state. (Stock, large valves, port to what extent if it applies, etc...

 

[THE STEVE]

i just put the stupidest cam i could in mine. it works great.