I have just finished my short block 347 with forged je piston and billet rods, stock compression, goin to use about a 100 shot of nitrous. Stock heads with 921 springs, AZ power and sound told me to use a big duration cam with high lift but, I herd if i go to big the heads wont support the power. The cam I have in mind is from comp its is a .605 intake, .609 exhuast with a 238 duration intake, and a 240 exhuast. Now im also worried about the valves will I need to have the piston cut so that valve wont hit.

Any suggestion will help thanks- I want a daily driven 11 sec car just so you know what my goals are

 

you dont need a 238/240 to reach 11 seconds and that cam in a 347 will not be so dd freindly. Thats my opinion. Now there are those who drive bigger cams on a 346 and say its perfect on the street but their idea of "perfect" is a lot different than mine. My numbers are in my sig. Your low and mid range power will be lower. Which is not street friendly.