Eric's cam challenge

92b said

Interesting. I haven't heard of this. Wonder why they didn't just measure the @ .050" specs? Unless this comes from a time back before it was common to do so. Maybe this was used as a way to compare data from old catalogs or something?
It seems odd to provide a formula to calculate the @ .050" specs and then state "do not use". Unless all cams were ground with the same profile from seat to @ .050" ...
Nevermind, looking at it from todays perspective the whole idea seems short sighted but I kind of get why they may have done this.

Click to expand...

They didn't start printing that in the catalogs until the late '80's when the duration @.050" became a "thing", up until the mid/late '80's the average guy didn't know about or hear it referenced often, or care. Mopar had settled on a basic lift rate by then, & that conversion was a pretty close hit on the actual measured duration, but......
If Your PurpleShaft is rated 280°@.015"Adv., but Your Comp Hi Energy is 280°@.006"Adv., they didn't want You correlating the cams because of either similar Adv. or @.050" ratings...they definitely will not perform or idle the same. Hence, they wanted You to follow the racer science formulas to select the right PurpleShaft for the job.