Lobe separation angles and the 300

[Walken100]

Testing my understanding. The program I'm using is https://mgispeedware.com/camshaft-calculator/. It doesn't differentiate between cam type when it builds a model. I'm just playing with my understanding of a roller vs flat tappet cam profile with similar specs and LSA's. The one on the right is my attempt to create a roller cam profile (using the advertised duration). Am I on the right track?

 

[pmuller9]

Testing my understanding. The program I'm using is https://mgispeedware.com/camshaft-calculator/. It doesn't differentiate between cam type when it builds a model. I'm just playing with my understanding of a roller vs flat tappet cam profile with similar specs and LSA's. The one on the right is my attempt to create a roller cam profile (using the advertised duration). Am I on the right track?

No
You cannot design a lobe with only 5 degrees difference between advertised duration and the .050" duration
The rate of lifter acceleration is limited and begins at a gentler rate off the heal of the cam lobe.
Look at a listing for both flat tappet and roller cam lobe profiles to see the typical difference in the initial ramp rate.
The initial ramp rate is the ramp between the .006" and .050" lobe lift duration.

The .050" lobe duration is the dominate factor to determine the engines response.

 

[Walken100]

No
You cannot design a lobe with only 5 degrees difference between the .050" and advertised duration.
The rate of lifter acceleration is limited and begins at a more gentle rate off the heal of the cam lobe.
Look at a listing for both flat tappet and roller cam lobe profiles to see the typical difference.

The .050" lobe duration is the dominate factor to determine the engines response.

Roger. I was just digging into this even more and I noticed that flat tappets seem to have a more aggressive early ramp (very early on) and then the rollers get more aggressive.

 

[pmuller9]

Here is the mechanical roller cam lobe for the 300 six in the pulling truck.
Intake has 237 degrees of .050" duration, 267 advertised duration and .380" lobe lift.
Exhaust has 247 degrees of .050" duration, 277 advertised duration and .380" lobe lift.
106 LSA

 

[Walken100]

On the truck pulling engine, we decided it needed a lot of midrange torque and be able to pull to 6000 rpm.
We went with a solid lifter roller camshaft with a .050" duration of 237/247 degrees with a 106 LSA and .600" valve lift
It idles fairly smoothly at 1000 rpm and the ignition timing is locked at 32 degrees.
It makes a ton of torque from 1200 rpm to 5000 rpm and will pull to 6000 without the load of the sled.

First of thankyou for hanging in with me on this. Your picture is well timed. Regarding your pulling truck it appears to have a very wide torque curve. Everything I've read indicates the tighter lSA tightens the narrows the power band. Is that because the wider LSA allows the power band to move higher in rpm. So effectively the tighter LSA Improves the torque curve in the lower end of the rpm range but causes the horsepower to fall off sooner.

I believe much of my confusion is because I'm focusing too much on over lap vs intake closing/exhaust opening timing.


So my concept of "leaning into the torque capability of the 300" combined with the use of e85 allows my build to take advantage of a tighter LSA? Especially since I desire to limit my RPM to <6k.

Here is the mechanical roller cam lobe for the 300 six in the pulling truck.

Dam that looks different.

 

[pmuller9]

First of thankyou for hanging in with me on this. Your picture is well timed. Regarding your pulling truck it appears to have a very wide torque curve. Everything I've read indicates the tighter lSA tightens the narrows the power band. Is that because the wider LSA allows the power band to move higher in rpm. So effectively the tighter LSA Improves the torque curve in the lower end of the rpm range but causes the horsepower to fall off sooner.

I believe much of my confusion is because I'm focusing too much on over lap vs intake closing/exhaust opening timing.


So my concept of "leaning into the torque capability of the 300" combined with the use of e85 allows my build to take advantage of a tighter LSA? Especially since I desire to limit my RPM to <6k.

Yes, you have to look at all of the valve timing events of a particular cam profile and not just focus on the individual camshaft parameters.
The 106 LSA with the intake lobe center at 102 degrees ATDC closes the intake valve very early providing the low rpm torque.
The scavenging from the headers during the valve overlap period starts the intake cycle early which helps the upper end of the power band.
Looking at the physical cam lobe you can see the amount of time and distance the valve spends off the valve seat which is what we call the "area under the curve" which is where the huge amounts of torque throughout the power band comes from.

Dam that looks different.

Yep, it is wicked.