http://detroit.craigslist.org/okl/pts/1386037300.html
for those that don,t know heres a picture of that dual plane vortec intake (LINK ABOVE)
ok back to the problem,IM not directing this answer just at your engine but more as a teaching aid for ANYONE reading this, hopefully getting them to use the links and calculators on the site, and thinking about what their choices in components do for the combo they build...keep in mind its fairly RARE for a complete engine to exceed 90% of the parts combos potential based on several factors like flow rates and piston speeds so always build something with a bit more potential power than you need, as a general rule its consistently more difficult to exceed 1.1 horse power per cubic inch of displacement in an engine designed for street use, as you push the upper power potential limits.
400 REAR WHEEL HORSEPOWER will require about 480-500 flywheel horsepower , so lets look at a few factors
, in most cases a well laid out STREET engine combo will produce roughly similar torque and hp numbers, IE it will produce its peak hp and torque in the 4700-5800rpm band, so that you don,t need to spin the engine to 6500rpm 7500rpm to get peak power, which is a really good thing with a dual plane intake and vortec heads, as both are designed for max hp at well below 5000 rpm, UNDER IDEAL CONDITIONS, YOU'LL REACH SOME OF THESE NUMBERS, but the intake must flow as well or better than the heads and it REQUIRES a TUNED low restriction exhaust with headers that scavenge the cylinders efficiently, the correct cam timing, and not getting into detonation, etc, ans almost NO ONE, manages to build a combo that reaches 100% of the combined potential of all the components, and youll need to match the cars drive train, gearing, and stall speed to the engines power band.keep in mind the 383-388 will ALWAYS have an advantage because of its larger displacement, that advantage is generally in the 35-40 ft lbs range over a similar 350 displacement, over most of the mid rpm range, but keep in mind piston speeds and valve train control issues really limit the 3.75" stroke 383 style with hydraulic lifter combos to about 6300rpm
the formula for horse power is engine torque x rpm divided bye 5252
example
if you have 500 ft lbs of torque at 3900rpm....
500 ft lbs x 3900rpm /5252=371 hp
read these,THREADS AND SUB LIKED INFO and think thru your choices
viewtopic.php?f=52&t=796
viewtopic.php?f=52&t=333
viewtopic.php?f=53&t=2733&p=7098#p7098
viewtopic.php?f=38&t=1099&p=2152&hilit=volumetric#p2152
viewtopic.php?f=50&t=1652&p=3987&hilit=volumetric#p3987
viewtopic.php?f=56&t=185
http://www.blueprintengines.com/popular ... s&pc_id=67
one major factor will be limited air flow rates, and volumetric efficiency as rpms increase
ok what we find is that a stock small port vortec heads has a port cross section of 1.66 sq inches
with standard small port vortec heads peak flow and torque ,will vary some, with the compression ratio and cam duration selected, but with a cam designed for street rpm ranges will be reached at just over 3100-3600rpm on a 383, and at about 3400-4200rpm with a 350, and that torque level at least in an ideal combo will roughly be maintained or slightly increased until port stall becomes a restriction to volumetric efficiency
http://www.rbracing-rsr.com/runnertorquecalc.html
you MIGHT be able to make 1.25 ft lbs of tq at peak torque at the max port flow per cubic inch of displacement limited to pump gas octane fuel
so for a 350 thats 437 ft lbs at 3400rpm=283hp
so for a 383 thats 478 ft lbs at 3100rpm=283hp
but thats not where the port flow stalls
http://www.slowgt.com/Calc2.htm#MinCross
http://www.wallaceracing.com/max-rpm2.php
on a vortec head on a 350 thats at 5600rpm=465hp
on a vortec head on a 383 thats at 5200rpm=473hp
so your going to be just a bit restricted even in an ideal combo from your goal using the stock small port vortec heads in stock condition under those conditions
Potential HP based on Airflow (Hot Rod, Jun '99, p74):
Airflow at 28" of water x 0.257 x number of cylinders = potential HP
or required airflow based on HP:
HP / 0.257 / cylinders = required airflow
vortec heads flow about 230cfm peak=470hp peak, which matches the other calculation
btw the stock small port vortec heads don,t benefit significantly from effective cam lifts over about 0.550 or duration of over about 234 on the intake timing, simply because as the rpms increase the time available to allow the cylinders to fill decreases and port flow is limited
and in stock form the springs limit you to about a .470 lift, by about 5200rpm on a 383 its beginning to be almost hopeless
READ THESE THREE, ENGINE BUILD UPs and notice the common factors, in required head flow, etc,
http://airflowresearch.com/articles/article085/A-P1.htm
http://airflowresearch.com/articles/article031/A-P1.htm
viewtopic.php?f=69&t=1040&p=1943&hilit=206cc#p1943
play with the calculators, think thru the info,
and you'll find
the LARGE PORT VORTEC HEADS MEET YOUR GOAL EASILY IF MATCHED TO A 10.5:1 CPR 383 sbc combo and a CAM like this, add 1.6:1 roller rockers, provided the intake and exhaust also don,t provide a restriction, and you use a 3000rpm stall converter on that th400 with that 3.42 rear gear ratio, and realize the power curve with the larger heads will be about 3000rpm-6200rpm with that cam, but you'll get to the 400 rear wheel hp goal if everything's done correctly
Large-Port Vortec Cylinder Head Flow
INTAKE
EXHAUST
Lift Volume Lift Volume
0.200 128.6 0.200 100.8
0.300 188.4 0.300 138.6
0.400 234.8 0.400 154.4
0.500 257.2 0.500 152.5
0.600 263.2 0.600 163.8
0.700 269.1 0.700 167.0
http://www.crower.com/misc/cam_spec/cam ... 1&x=51&y=9
http://www.rpmmachine.com/383-chevy-for ... r-sb.shtml
http://www.adperformance.com/index.php? ... th=277_278
QUESTIONS?< DISCUSSION?