im not sure what cam i have in my engine. i bought a 71 240z that had a L28 engine, 5speed trany, upgrades supsension, 2.5" exhaust, and various other parts. i am trying to figure out what has been done to the engine.

See if there is a letter stamped on to the back of the cam - http://atlanticz.ca/zclub/techtips/cam/index.htm

Find the letter/numbers stamped/engraved on the cylinder head, above the 1 and 2 spark plugs (E88, P79, P90, N42, N47...).

See if you can find the letter/numbers molded in to the bottom of the block, almost behind the driver's side motor mount, right above the oil pan lip (N42 or F54).

Post all of this information and people will tell you what you're working with.

im still not sure on the cam, but i have a n42 block with a e31 head. so far the things i know about the engine is that it has a performance clutch, e31 head n42 block, dual su carbs, headers, and not sure about the internals on the engine.

That's not a factory blend of parts. You have an L24/240Z head on an L28/280Z block. You'll have to pop the valve cover off and look for identifying marks on the cam. If I had to guess, I would say that it's the cam that came with the E31 head, which would have an A stamped on the back, according the link I posted. The simplest option, just a different block with the old head and carbs (although I'm no expert on what head or carbs came on a 71 240Z so could be way off).

Pics of the car??