my 340 challenger

im building a 340  030 over 12.5 comp  j heads 2.02  int 1.60 ext milled .020 very nice port job bowls blended and so forth  cam is mp .590lift 312 dur  open single plane int 800cfm dp timming set to 36 deg total  does anybody out there have an estimated horse power  figure  for me  thanks you for any help sent my way   ill have pics soon                                           mopartim85  

312 duration??? Why???? This is a drag motor I will ausume. So unless you have a 5500 RPM converter you better reconsider this cam, even with the high compression.
boring the motor is worth almost nothing unless the cyls. are out of round. J heads ported and polished very nice, but the fact is they fall off after .550 lift so any more is a waist of time.
800 CFM carb is worth 1-3 hp over a 750 at 6000 RPM, again a waist of time especially on the 340.
If you want a strong running 340 with cast iron heads then you need to stick to some basics. First is, NEVER exceed 290 duration in a drag motor unless you have a pro-mod budget to make it work.
Max duration 286/243 at .050 and 540/550 lift, solid or roller.
Comp. 12.5 with racing gas is fine.
J-heads ported and polished to the max, 2.05/1.60 valves.
1.5 roller rockers.
I beam rods are lighter and faster and good to 6500 rpm. H-beam rods if you want to spin it to 7000+ rpm.
75 lbs operating oil pressure.
1 3/4" headers.
My preference for an intake, air-gap with a 1" divided in the center carb spacer. I have seen this intake out run a Victor time and time again. Why, it simply has better low and mid range power. If you insist on a single plan intake the M-1 is good for 540 HP in stock form.  
750 Holley Double pumper with the HP main body, 72/82 Jets, 6.5" power valve, 45 thou. shooters.
MSD 6AL ign.
4200 9 1/2" dynamic converter.
4.57 gear with a spool or clutch type posi.
Moser axles.
28x12.5 slick.
530/540 HP    
Hang on cause this thing will yank the wheels a foot in the air and run mid 11's in a E body.
 Same combination can be done with a 360 LA motor and you will get even better  results. In fact the 360 will out perform the 340 in a heavy car every time.  
Want more? Eddy heads, ported to the max, 290/600" lift cam, Victor intake, 1 7/8" headers. 600+HP.
Of course both combos will need racing gas with the high comp. You can run an extra 1/2 point of compression with the aluminum heads, however 12.5 is plenty.  
Good Luck
Doc