Unheard of to me, Robin ripped off tests with only 50 minutes elapsed from cam to cam! This highlights the importance of good and repeatable testing procedures. We also recognized that each cam would ideally have its own proper calibration to fully optimize it, but the general tune utilized was checked with each new cam to verify it was still in the ballpark. As many argue on the forums, the calibration or tune is another area that offers a range of options that can balance (or weight to different extremes) durability or performance. A safe dyno calibration was created for the purposes of this testing that targeted 13:1 air/fuel ratio and a maximum of 28 degrees of spark. For street use an even richer A/F ratio may be necessary.
An important question when installing a new cam in an otherwise production engine, is whether the valves will hit the piston with the increased duration and tightened centerlines. We checked the biggest cam with the tightest LSA (that subsequently was not chosen for the test because of too much cam overlap) to verify piston to valve clearance. With a 232/246-duration, 0.614/0.619-inch lift on a 112 LSA, this cam still had 0.100-inch clearance on the intake valve and 0.120-inch on the exhaust valve. We generally like to see at least 0.080-0.100-inch clearance on the intake and 0.100-0.120-inch on the exhaust, depending on how brave you are and how confident you are the valvetrain is in control.
As one would guess from the range of cams that were submitted, the power results varied a lot as well. Remember that peak power is not necessarily the only factor considered here. If it were, all the suppliers would have provided much different camshafts. When stepping back and looking at the results on a whole-the test cams averaged an improvement over the LS3 of 24.5 horsepower and 23 lb-ft of torque over the entire 3,000-6,700 rpm test range. Peak power gains ranged all the way up to 70 horsepower! While peak power is nice, most driving doesn't occur at 6,200 rpm, so area under the curve is important for seat-of-the-pants enjoyment. So we looked at the area under the curve for various regions of the curve. We would like to evaluate even lower, but often on water brake dynos it can be difficult to properly control WOT runs at 2,000 rpm or lower.
When it comes to identifying how these cams would impact driving manners, we monitored the MAP values with HP Tuners VCM Scanner for each cam. Closely following the MAP values, Robin said he noticed a difference in some cams on the dyno-the lowest MAP value Lingenfelter cam "purrs like a kitten," the Mast Motorsports cam was very smooth, and at the opposite end of the spectrum the Livernois and Lunati cams "had significant lope." The trend of higher MAP values with larger overlap values are clear from this testing. To try to put all this into perspective and correlate the subjective term of "driveability" into some objective, measurable format we created this cross-reference chart based on experience, the data discovered here and input from other experts in the calibration/cam design field. Some of the bigger cams with higher MAP at idle oscillated more when coming off wide open throttle, another indicator it would experience some instability in the car, putting it into a lower "driveability" scale level.