This isnt exactly a thirdgen question, but is basic engine. How do you tell if a car has an aftermarket cam in it? I know not all have lopey idles, so its tough. A friend of mine with a 95 Z28 6-spd bought his car allready slightly modified. He thinks he has a cam in it and thats why he didnt pass emissions. He said his mechanic ran the car on the emissions dyno and used the computer and told him it was his cam that did it. Thanks for clearing this up.
Matt

 

the biggest way you could tell would be to take it out, and measure the lift. Thats the only way, or if you are beating vipers left and right, and he sweras all he has is intake and exhaust.

 

You can mount a dial indicator on the top of the heads over the rocker (pushrod end) and measure the cam lift. while rotating the motor. Multiply your measurement by 1.5 = valve lift.
Hyd lifter bleed down may or may not squew your measurement a little, but if it comes out to more than stock lift for that motor, you can be pretty sure it's been replaced with something.