Ok i have a 68 chevelle with a 327 im having slight engine problems when i hit 40mph in first gear i start to backfire. Or when im in park and i rev my engine to high RPM's its back fires.It also feels like i lost alot of power.Does anybody know what can be causing this im thinking its my spark plug wires. Please help.

You shouldn't sit there and rev to high rpms.

Distributor loose/timing off?

Point bounce? Valve spring bounce?

Another thing to try, wait until its good and dark, and start it up and look very closely at the spark plug wires, sometimes if there bad you can see them arching, have somebody with you watching you so you don't get your head or fingers in the belts or fan, I'm serious about that, when you're looking you tend to forget what you're doing.

Clencher mentioned points also, I used to have one that would do the same thing, I would set the points with a dwell meter, and it would still miss at higher rpms, then I would have to change the point gap a couple times to get the miss out, and use new points and condenser.

Rob

If the engine has a lot of miles the camshaft could have some badly worn lobes.
Paul