jeepsr4ever wroteThe factory cams are as follows
304/360 Intake duration 263.5
401 intake duration 296.32
304/360 Intake duration 263.5
401 intake duration 303.55
Valve overlap
304/360 41.5
401 68.32
Cam lift
304/360 .266
401 .286
Here is my experience with the 256xe. Every single one I have used or sold minus one (Donwag) have had low power at idle and dumped off at 3200rpm. They have been a huge dissapointment. The 256Xe specs are as follows
Duration 256/268
Lift .477/.484
We have had bad experiences building power with this cam over stock and we believe it is due to the low lift and duration. On the flipside we had great experience on a 304 with a Edelbrock performer camshaft, mixed results with a 360 and poor results with a 401. Here are the numbers for the Edelbrock.
Duration 278/ 288
Lift .448/ .472
Do you know what he .050 duration is for the stock cams?
The XE256 and Edelbrock performer cams both have an LSA of 110. Narrow LSA's tend to make the torque curve peakier, increase overlap, and decrease low end torque.
Longer LSA's tend to extend the torque curve out the rpm range and build better low end vacuum and torque. It is my "feeling" that an LSA of 112 or better is more suited to AMC engines. Perhaps it is the shorter LSA of 110 that is the reason for mixed results with the performer and XE256.
The LSA for a stock 401 cam is 116, for a stock 360 cam LSA is 113.
Here are the general effects of LSA on cam performance:
LSA Effects, Narrow, Wide
Intake Open, Earlier, Later
Intake Close, Earlier, Later
Exhaust Open, Later, Earlier
Exhaust Close, Later, Earlier
Overlap, More, Less
Cylinder Pressure, Gain, Lose
Idle Quality, Worse, Better
Idle Vacuum, Less, More
Torque Curve, Peakier, Flatter
Peak Torque, More, Less
High RPM, Drops Off ,Hangs On
The effects of longer LSA is why I generally recommend what may seem like relatively shorter duration cams - in order to close the intake valve sooner to help build/retain cylinder pressure and the longer LSA to extend the torque curve.
