installed new Pertronex ignitor and coil in 1971 240 works great but, tach drops off at 4000 rpm when engine revs higher. Jumps up to 4000 rpm when revs drop below 4000. do I need another resistor and where do I get it?

I have a '72 with a Pertronix & it works great, no tach issues. Check out http://www.zhome.com/ZCMnL/tech/ZXPertronix.htm & make sure you follow their wiring diagram.

Thanks Dave, I`ll check my wiring....

Did you eliminate the ballast resistor? I have to check mine, but I think even if you go with a 3 Ohm coil, you need it for the tach. Correct me if I get this wrong.