For our dyno testing I want to get a camshaft made to optimize power with one of our combinations (meaning heads, intake, etc) with the restrictions that I want to limit the engine 6500 RPM, I don't want to change the compression ratio (currently mid 10's) and I am not changing pistons to put valve reliefs in them (so that cam must work with our current 0.320" valve closed to valve touching piston). There are two ways this can go. I can get a camshaft that optimizes peak horsepower but less "area under the curve" or get a camshaft that optimizes the area under the curve. In the last write up I started putting in average HP and TQ for the entire pull, this would be area under the curve.

The cam will probably be mid 0.600s" for lift and duration around 260/270 intake/exhaust at 0.050". I feel, along with a few camshaft designers, that this would be optimal. The peak HP or area under the curve comes with lobe separation angle, LSA. I have seen cams have as much as 30 more peak HP with the right LSA, but less power and torque in the lower RPM range. Which one is faster in a car depends on weight, gearing, etc.

I'm trying to make this a poll, but I doubt I have the ability to do that....

Peak HP Camshaft

Area Under the Curve Camshaft

 

The answer is area under the curve from redline to whatever RPM the next gear picks up. If you shift at 6500 RPM and the next gear picks up at 5000 RPM, it really doesn't matter what happens below that (for outright acceleration). Calculate how far your RPMs are going to fall when you shift, and optimize for that specific area. Anything below that doesn't matter in the slightest for drag racing.

Now for street driving or road racing, you may care what happens below that range.

 

It's like picking a torque converter. How close can you get? Very few will nail it off car specs.
Personally, I'm used to too-rowdy-for-a-street-car vs roo-slow-to-be-a-racecar

 

Actually the right cam will give you both.

 

Jerry I really respect what you are doing for our community. Keep up the good work. If you need a hand reach out. I'm always willing to learn some new things.

 

I like a fatter curve than a peaky one or one with big dips in them.
Street /strip that is 90% street use. power at the rpm's you'll be driving at normally, is more useful than peak power that it rarely spin to that rpm.
Torque moves you, h/p sells cars and gives you one hell of a top end charge. Odds are your ability to use that top end charge on the public roads is very limited.
A fat meaty curve with the bulk of the power production from 2000 to 4800 rpm will be better for all aroud driving on the street. You'll win no ego driven bench racing but who cares.
I have one engine that is MEH till 3400rpm then off like a bullet, fun to drive but not all that fun under normal street driving. Breaking traction when trying to overtake/pass someone is not for the faint at heart. I had not driven it in two years and forgot all about it being like a switch at 3400 rpm ish. and tried to pass another car and went sideways while making the pass. Part if it was the engine set up. the other part was 3y/o tires that were still cold. white knuckle event. peaky power band can be fun, but you best be ready for it when it gets on the cam.

 

how can you say any of that without knowing the starting rpm of the pull? he told you the end rpm which is 6500, but not the start rpm . Typically dyno pulls are much wider than the gear rpm spread or drop between gears. it’s on the dyno, not going through gears on the street.

the rpm spread needs to be known for area under curve cam.

 

@CANADIANOLDS Welcome back Captain negativity. Peak power for sure @JerryW

 

your goals are unclear. you need to be specific on why you’re doing this. simply saying I want to pick two cams, one for area under the curve and the other for peak hp doesn’t mean much. it’s either one or the other, you can’t compare two different situations against each other.

cam designers would also need to know your goals. area under the curve usually involves a much wider rpm band than peak hp alone.

drag, street, road race, marine, etc all require different cams for each specific purpose.

the poll needs to be specific on which cam would be best for each situation…my two cam choices would be completely different going off a rough guess on what you want to accomplish.

RPM range

 

The poll would end up being two wildly different cams based on the RPM band and goals.

sorry, that’s the truth. don’t mean to hurt anyone one’s feelings

 

By saying what I said in the first sentence. Maybe try reading.

And as I said, in the third sentence, he needs to calculate that. Maybe try reading.

Really? You don't say?

As I said in the fourth and fifth sentences, my answer is specifically related to what would be faster and in what specific context. Maybe try reading.

You mean an RPM spread like the hypothetical I used in the second sentence? Maybe try reading.

 

well then, I stand corrected

I wonder why CKPerf says peak power, but you say area under the curve? I’m trying to learn, are you right, or him?

 

that’s quite the assessment when you don’t know any of the details. maybe it’s going in a full weight A body with 3:23 gears and a factory converter?

Jerry has you and Bubbles, I mean Bubba, guessing in the wind. he says he would like to find out which one is fastest in a car, depending on weight bearing etc.

or maybe it’s just a dyno mule to get the best averages over a wide rpm band?

 

Maybe instead of being on Jerry's jock in every thread he starts that you trash.
Go do your own testing and report back.

 

I like what Jerry is attempting to do here. he said something about figuring out which type of cam would perform better , depending on the weight, gearing etc. that’s all key in picking a cam.

so he does know the drivetrain details need to be known. If you ask any cam expert , would a peak hp cam or one that’s designed for a broader power curve , be faster down the track? …the very first thing they would ask is the details about the car and drivetrain

you’re offended for no reason

 

No you're not.