Cam Question...

[themadgmkillr]

Don't know much about cams so I thought I would get learned... :rolling:

What makes a cam more agressive in the lopey category...and what are you really looking for or doing to the motor when installing more aggressive cams...

Which one of these would we say is more aggressive, or better for a weekend warrior

258/254 @ .050 Duration .472/.472 Lift 109 LSA
233/237 @ .050 Duration .545/.550 Lift 113 LSA

 

[lemosley01]

1) The 4V's don't need more lift - they like more duration.

Now, the next stuff I'm kind of sure on, but not 100% - someone else who knows more can chime in and break my balls. I'm posting it to see if I got my thinking correct.
1) Lopey idles are basically a function over intake and exhaust valve overlap. The more overlap you have, the more 'lopey' an engine is.
2) More duration is what makes a cam 'aggressive' (given the same lift). When it comes to more lift, less duration, I am not sure. I believe the first cam will be more aggressive. I believe that duration affects overlap, or maybe that is the centerline angle. I get all of these terms confused at times.

A more aggressive cam moves the peak horsepower and peak torque higher into the RPM range. This is important for racing because that is where you (want to) spend your time at. However, at lower RPMs you will sacrifice horsepower and torque. A less aggressive cam moves the torque/horsepower peaks lower into the RPM range, but falls of as the RPMs pick up.

A good 'streetable' cam is one that has good low-end and midrange RPM power and torque - the low and middle RPMs is where you spend most of your time on the stree.t

The current Mach 1/03/Navigator intake cams are GENERALLY considered better street cams because they have good low and middle range horsepower and torque.

The 99/01 intake cams are more aggressive and are considered better for strip/track duty because they thrive in the upper RPMs, but give up the power on the low and midrange.

Hope I got that right. Cams are a fascinating subject to me, but also somewhat of a black art.

 

[lemosley01]

A weekend warrior would probably be happy with the first set of cams you listed, although I don't know that you need that much lift. I believe the stock lift is .39" or so. You can't increase lift too much without having to replace your springs, although, with either of those cams, you would probably want to go with new springs anyway so you can rev the engine higher.

 

[Torch10th]

I don't know if I'd go with either of those cams honestly. the 109 degree LSA scares the shit out of me on these motors. They're already peaky as hell, that 109 LSA is going to make power in an even narrower power-band than stock.

If anything I'd choose the second. It's a bit less aggressive but based on the lift would lend well to a ported head. It's also got the wider LSA which will help spread the torque over a broader rpm band.

 

[lemosley01]

LSA controls how broad the torque band is, then

 

[Torch10th]

LSA controls how broad the torque band is, then

At the sacrafice of peak numbers yes. You can play with it a bit though using cam timing.

The first cam listed above is going to make good power, but it's going to be very peaky. It'll likely have a power curve similiar to a single turbo supra. For a street car you'll probably be slower because of the lack of low-end

The second cam choice will keep power lower in the power band. It won't make as much power, and certainly won't sound as nasty as the first cam, but it will keep some low-end grunt in the engine and for a street car this is really what you want.

You'd need an insane gear and probably more compression with cam #1

 

[lemosley01]

He did say 'weekend warrior' - my assumption was he was taking it out on weekends to the track.

Stock duration is like 194, isn't it? Those cams definitely have an assload more duration.

madge, are those from crower or comp, or what?

 

[Torch10th]

The first one is definitely a strip cam. You'd be launching off the limiter with slicks with a cam like that. It's useless elsewhere in the powerband

The first cam has a total of 38 degrees of overlap. It's an absolute monster. It would likely make power well past 7000 rpm so on a stock shortblock it's not going to work well.

The second cam has 9 degrees of overlap. It's probably in the neighborhood of the fr500 cams. Probably a good blower cam, iffy for a turbocharger cam.

 

[themadgmkillr]

well the first is the 500 set-up and the second is a stage 2 from patriot

 

[Torch10th]

well the first is the 500 set-up and the second is a stage 2 from patriot

This is probably due to being dual overhead cam. The characteristics likely change. That stick in pushrod motor would be pretty large.

So I'm just going to go burry myself in books for overhead cam design. :cuss: