The motor runs great driving around and at idle, but when trying to launch the car the motor jumps then falls on its face. This is random sometimes it has full power , other times it misses hard. I think the ignition is breaking up somewhere but I could be wrong. Stock block and heads, new comp cam, edlebrock intake and 600 cfm carb, msd streetfire ingnition box, msd wires, accel coil and plugs all new stuff. any help would be great because its so random its hard to figure out.

 

When was the carb last rebuilt, and tuned? What kind of fuel pump?

 

New Edelbrock 600cfm , been tuned and its a stock fuel pump

 

A few things to look at and try....there's an arm (accelerator pump) on the drivers side front with 3 holes. Yours is probably in the middle one. See if moving it to the one closer to the carb body helps. Also, I had a similar situation when I was dialing in my 312. Turned out the new stock fuel pump was NOT up to the task of supplying fuel at anything beyond idle and light to almost moderate fueling. Upgraded to a Holley 130gph, and problem was almost completely solved, minus some more adjusting.

Also, where is your vacuum being referenced on the carb? Move it to the other vacuum port and see if that helps at all.

Speaking of timing, how are your cap, rotor, ignition module, etc? Are those new too?

 

Timing is set is at 12 degrees , new cap and rotor and accel coil. Ignition module was replaced with the streetfire ignition box. Would that cause a problem? Like sometime it will pull hard and other times it will fall on its face?