I just rebuilt a 396 and put the performer rpm heads, intake, and cam.(240-246, .560-.573) I also installed a new Holley 750cfm doublepumper, and msd ignion, with the lightest springs installed. I can't get the thing to idle right, when I get it going, it eventually stalls, got the secondaries cracked, used a vacccum gauge to set idle curcuit. The engine seems to want more timing than usual. 10-1 compression. I have alot of steam blowby coming from the valve covers, at mid throttle,2000-2500 rpm, the engine pops and surges, have dual 2.25 exhaust, (too small?) also, doesn't seem to me it has 450hp as it should, very little take off power, (stall converter is 2600, but feels much lower, also wants to stall when in gear (3.55-1), how much timing should I be shooting for? am My jets to small?, plugs look brown, but ok. any help would save a sane man.