. The guys have pretty well zero'd in on your problem... likely carb. secondaries opening while spinning tires at higher RPMs, but then when it hooks up, RPMs drop down too low for all 4 bbl.s to be open yet... tightening up the spring slightly on the secondaries may cure that... also, when racing, avoid spinning the tires/engine RPMs so high that the secondaries open too soon... your carb. size is about perfect, as the other guys said... those calculators are for stock engines with higher vacuum, for a mild performance engine we go about 10-15% bigger in air flow CFM...
. Also, at the same time, your torque converter stall RPMs may be too low for that getting biggish 230/236 cam (way down at 196/206 durations is about basic stock)... when the tires bite, they may be pulling the engine down out of it's powerband... creating some 'falling off the cam' bog... prolly need at least 2500 RPM stall converter for that cam size... you can powerbrake up and get an idea of your converter's stall RPM range if you have a tach... your rear end ratio and rear tire size also figures into this... you can put the rear axle up onto safety stands and rotate the driveshaft to find the rear end ratio... measure the tire diameter or give the size numbers off the side... also, vehicle weight is a factor...
. This engine sounds like it was built identical to the famous Hot Rod 6 part HT383 build up... they got 460+ HP and 500+ lb.-ft. torque with your combo... (and a slightly 'happy' dyno?)
GM HT383 Crate Small-Block - Engine Build - Hot Rod Magazine
. We call it a "mild" build because it isn't an all out finicky irritating race combo, or near a stock build, either, but a good, strong, still fairly tractable, fun budget street/strip build... (as opposed to strip/street build which is biased more toward the strip)... nobody meant to insult you or your vehicle...
. As also mentioned, since this is a truck and you prolly have room up top, double up the air filters stack... (also looks impressive, LOL!)
. You need tire size and rear axle ratio close to right to let the engine rev into it's powerband in all 3 gears by the end of the 1/4 mile for best performance... but with those Vortec heads, RPMs won't be real high with 383" to feed... also, you need to be shifting at RPMs above the HP peak for peak performance, say, at least 6,000+ RPMs... do you have a tach? This calculator provides a great spread sheet of theoretical RPMs in gears vs MPH...
http://www.F-Body.org/gears (hit 'clear right' button before doing anything)
. I've seen complaints before about this particular combo, especially concerning low RPMs torque with that big of a cam, Hot Rod posted some surprisingly impressive torque numbers for 2500 RPMs, but they used an expensive annular boosters carb. with better than average low RPMs metering to get those numbers that strong that low... and a lot of precise dyno tuning... and so the typical owner of this combo prolly isn't getting as much low RPM torque as they expected from the article...:
No power 383- built similar to HOTROD HT383 build Page1 - General Chevy Technical Discussion Forums at Chevy High Performance Magazine
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