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"Major Intensity", a marketing tool

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Location: Denver, NC

"Major Intensity", a marketing tool

Post by CamKing » Tue Jul 16, 2019 11:14 am

Harvey Crane was no slouch, when it came to marketing. To promote his cams, as being more aggressive, he invented "Major Intensity".
Major Intensity is the number you get, when you subtract the cam's duration at .050" Tappet lift, from the duration at .020" tappet lift.
His sales pitch was, the smaller the Major Intensity number, the quicker and more aggressive the cam was.
Problem is, since .020" duration, and .050" duration to not account for different lash ramp heights, The Major Intensity number can be easily manipulated.

Here's an example.
Cam A: 288@ .020", 260@ .050", 181@ .200", .425" lobe Major Intensity= 28
Cam B: 296@ .020", 263@ .050", 182@ .200", .430" lobe Major Intensity= 33
Cam C: 291@ .020", 261@ .050", 181.5@ .200", .427" lobe Major Intensity= 30
Looking at the Major Intensity numbers, cam-A looks to be the most aggressive.

What you don't know by looking at the cams above, is all 3 have different height lash ramps, and different Hot Lash settings.
Hot Lash for cam-A is .016", cam-B is .024", and cam-C is .019".
So now, let's look at the cams, at the valve, with the correct lash settings for each cam.

These are at Valve Lifts with Lash
Cam A: 285 @.020", 267 @.050", 182 @.300", 119 @.500", .664" Net Valve Lift
Cam B: 285 @.020", 267 @.050", 182 @.300", 119 @.500", .664" Net Valve Lift
Cam C: 285 @.020", 267 @.050", 182 @.300", 119 @.500", .664" Net Valve Lift
With lash, these 3 cams look identical, when checking durations at various lifts.

Looking at the durations at the valve, with lash, you would think all 3 cams will perform the same, and that they have the same aggressiveness.
Here's what looking at just durations at varius lifts, doesn't tell you.Here's the Max Velocity and Acceleration on all 3 cams
Cam A: Max Vel-.008598", Max Acc-.000106"
Cam B: Max Vel-.008598", Max Acc-.000106"
Cam C: Max Vel-.008894", Max Acc-.000114"
Cams A & B are symmetrical, and would perform the same. Cam C is asymmetrical, and even though it has the same durations at the various lift points as A & B, it opens quicker, and closes slower then cams A & B

From all the duration data I gave, both at the cam, and at the valve, there was nothing to suggest cam C was the better choice, and if you looked at Major Intensity, you would think it was less aggressive then Cam A.
Now lets look at these cams at the valve(with Lash) on a 104 ICL.

Cams A & B:
open .000"@ 52 BTDC
open .020"@ 38.5 BTDC
open .050"@ 29.5 BTDC
open .300"@ 13 ATDC
open .500"@ 44.5 ATDC
close .500"@ 16.5 BBDC
close .300"@ 15 ABDC
close .050"@ 57.5 ABDC
close .020"@ 66.5 ABDC
close .000"@ 80 ABDC

Cams C:
open .000"@ 52 BTDC
open .020"@ 39 BTDC
open .050"@ 30.5 BTDC
open .300"@ 10.5 ATDC
open .500"@ 40.5 ATDC
close .500"@ 20.5 BBDC
close .300"@ 12.5 ABDC
close .050"@ 56.5 ABDC
close .020"@ 66 ABDC
close .000"@ 80 ABDC

Notice how cam C gets from .000" valve lift to .500" valve lift, 4 degrees sooner then cams A & B. That can equal a very big power gain, and if you followed "Major Intensity", you would have missed out on that power gain.
Mike Jones
Jones Cam Designs

Denver, NC
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44

Posts: 32
Joined: Wed Jul 17, 2019 2:56 pm

Re: "Major Intensity", a marketing tool

Post by Outlaw383 » Thu Jul 16, 2020 5:04 pm

Very eye opening and a perfect explanation Mike. I read an article somewhere a few years
ago that basically used the same method you described (major intensity ) .050 vs .020 for deciding which cam was most aggressive.
Thanks for clearing it up.


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