when the car is in park it idles around 700rpm when i put it in drive it idles between 500 and 700 and is rough . what could this be?

 

You might need to elaborate a bit more on the problem.
What duration of cam?
Did you reprogram the prom and tune to this size engine?
Did it idle properly before and this just started?
Are you running a single wire O2 sensor on headers too far away from the head? Your O2 sensor might not be hot enough.
Is timing, IAC, TPS properly adjusted?

 

i have an lt4 hotcam,stock chip i know that doesnt help,did it with stock motor but lot worse til i got new relays and maf sensor,y o2 sensor is where the cat would be, timing and sensors are good

 

bump

 

I would start off with the tune (that stock chip may not be doing the trick) data log the car to see what it is doing and start there. that o2 sensor may be too far away, mine is in front of the header collector, drivers side.

good luck

 

Until the prom is modified to run a 383 with a 219 duration cam, it's going to run very poorly, especially at lower rpms. The prom is set to feed 350ci and the long cam duration is signaling the engine is under load and needs more gas.

I wouldn't run that engine without at least setting the prom to feed the correct displacement.

Single wire O2 sensors installed down at the collector flange are probably too far away to keep at proper temp, especially at idle. Try a 3 wire heated O2 sensor.

 

thanks

 

if it did it with the stock motor as well, it could be the distributor acting up... does it ever try to stall?