is there any difference other than the obvious with these two cams?

the obvious being the cam lift, and the water pump...

im more refereing to the valve timing, and the inability to start my engine with a sigma cam - and it sounding like the timing is out...

i thought the astron cams were all the same, except for the water pump provisioning.

Most Sigma/Scorpion Motors ran mechanically adjustable rockers whereas the magnas ran hydraulic.
The cam profiles vary quite substantially between the two, not just in lift but also in ramp angles, durations and overall timing specs. Manual/solid cams should not be run as hydraulic they are not designed to do that.
I am assuming you run the hydraulic rockers and have put in a mechanical rocker cam?
I believe this is your problem.
As a start, it would be worth checking your valve timing for correct positioning of the cam. I have seen cams ground up to 10 degrees retarded which will generally not help. If it is a reground cam the base circle can sometimes be decreased to the point where you have too much valve clearance and it stuffs your valve geometry.
Simple solution is to get a cam specifically ground for a Magna.

yeah, i had the chance to try this cam out in my car to i could get an idea if a cam is worth getting.

i wasn't gonna run it for a long time, just enough to get an idea.

i'll have to check out the two cams side by side.

turns out the dizzy had a problem with it... all fixed...

now i have to get a lumpy cam of my own :D :D :D