We started our testing with Mopar’s small Purple Shaft (PN 4120655). After a few pulls of
Next on our list was the next larger Mopar grind, the 590 camshaft PN 4120657. With duration at .050 inch of 271 degrees, lift of .629 inch, and a lobe separation of 106 degrees, Mopar recommends this camshaft be installed at 104 degrees. This camshaft has a good reputation as an excellent bracket-racing camshaft, and we can see why. Boasting a peak torque of 572.2 at 4,800 rpm, and a horsepower peak of 596.9 at 6,600 rpm, this was a definite step in the right direction.
We also tested a camshaft from Hughes Engines to compare to the MP590, PN HTL6468AS. This camshaft features a split duration of 264 degrees at .050 inch on the intake, and 268 degrees at .050 inch on the exhaust, lift numbers of .634 inch intake and .651 inch exhaust, and lobe separation of 106 degrees. It was installed at the recommended 103-degree centerline. Proving to be a very nice grind for our engine with a nice torque curve and a very strong top end, our torque reading came in with a peak of 573.4 at 4,800 rpm. Our horsepower peak of 617.1 came in at 6,600rpm.
Horsepower comparison of Comp Cams 20-632-5 and MP's 620.
Torque comparison of Comp Cams' 20-632-5, and MP's 620
Lunati had sent their 404A4 grind for comparison. This cam had slightly less intake duration with 263 degrees at .050 inch, and exhaust duration of 271 degrees at .050 inch. Lift came in at .637 inch intake, and .661 inch exhaust. The lobe separation was again 106 degrees, and Lunati wanted it installed at 100-degree intake centerline. This camshaft performed pretty well with a torque peak of 563.4 at 4,800rpm, and a horsepower peak of 604.4 coming in at 6,900 rpm.
The final Mopar Performance grind tested was the now obsolete 620 grind, PN 4349266. Duration at .050 inch of 283 degrees on both the intake and exhaust lobes meant this camshaft was designed for high rpm use. Our lift numbers were .636 inch. This cam was ground on a 106-degree lobe separation, and was installed at Mopar's recommended 104 degrees. The torque dropped substantially throughout the range, and our horsepower level was also low, only managing to get a peak torque of 548.3 at 5,100 rpm, and a peak horsepower of 595.4 at 6,700 rpm.
Throughout all of our testing, each camshaft was degreed per the manufacturer’s instructio
Comp Cams suggested their TL300 grind, PN 20-632-5 as a performance upgrade for the MP 620, so we swapped it in for our final test. With duration numbers at .050 inch of 270 degrees on the intake side and 278 degrees on the exhaust side, and lift of .618 inch intake and .616 inch exhaust, it appeared to be a nice fit between the Mopar 590 and 620 grinds. Comp had their camshaft ground with a 108-degree lobe separation, and it was installed to their 108 degree recommendation. Peak torque came in at 5,100 rpm with a reading of 554.2, and horsepower came in with a peak of 581.2 at 6,500rpm.
It is interesting to note that even though some of the camshafts tested had very similar averages over the entire rpm range, many times either torque or horsepower was substantially higher at a certain point, which could really help in certain combinations. For example, if you run a car with limited traction, trading off some torque down low for more power up top may help your car out with a better et.
We can see by the test, that going larger in degrees of duration moves the engine's torque peak higher into the rpm range, until you reach a point of too much duration for your combination. Our ported heads seem to like as much lift as we could give them. Your combination will most likely be different than ours in some way, but the more commonly available 4.00-inch stroke builds should react pretty similar to our test engine given the same basic components.
|MP camshafts (sold as cam and lifter kits) PN 4120655 and PN 4120657
|Comp Cams 20-249-4
|Comp Cams 20-632-5