Part 2: Dynos Don't Lie
In December we outlined an engine recipe for a Chevy 350 that you could duplicateusing mostly junkyard parts that we theorized should have made about 400hp/ 400lb-ft. In reality, we were secretly thinking we'd make about 390-395hp and a little better than 400lb-ft. Well, as you can see from the dyno graphs, we didn't quite hit the mark. Regardless, this kind of power from simple, bolt-on parts thrown at a stock-type Chevy 350 short block isn't too shabby.
The GM Performance 290hp 350 crate engine we used proved itself as durable as an anvil. We mercilessly beat it with almost two hundred full-throttle, full-load dyno pulls up to 6,500rpm, and a couple up to nearly 7,000rpm. And it held. As for our camshaft selection, we'll admit that the Lunati Voodoo 268 grind is a bit gnarly for our cylinder heads. Even with our Lunati PN 74818 springs set up to deliver a burly 155lbs-seat and 330lbs-open spring pressures, we still ran into some valvetrain harmonic issues between 5,300 and 6,000rpm. This caused a dip in the power levels right where our peak horsepower would've been found. Ideally, if we were to do this over again, we'd probably select a Voodoo cam with a shorter 219/227 duration @ 0.050 and .468/.489-inch lift (PN 60102), or even one of Lunati's new Street/Strip cams with a less-aggressive lobe profile offering 223/231 duration @ 0.050 and .463/.485 lift (PN 301A9LUN). Either probably wouldn't cost us much (if any) top end power, and would serve to fatten up the torque curve a bit.
In the end are we unhappy? Well, yeah. Even though we upped our crate engine by 72hp and 57lb-ft, and even though you can technically duplicate this engine for just over $1,200, we really wanted to reach that magic 400hp/400lb-ft mark. Regardless, we wound up with more power than most crate engines out there at roughly half the price. So for what it's worth, here's the result of a couple days' worth of spinning wrenches and pistons on the Westech Performance dyno, dozens of gallons of Rockett-brand racing fuel, and a good amount of stomach lining.
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Want to duplicate our combo? Even though we used a solid and dependable 290hp 350 crate engine and brand-new Vortec heads from GM Performance Parts as our base for this buildup, you could theoretically substitute a decent $100 junkyard 350 shortblock from any '70s-'90s GM car or truck, a set of $180 Vortec heads from the boneyard, and use cheap stock valve covers and fasteners where applicable to duplicate this combo for less than $1,250. Prices were found online as of press time through Pace Performance or Summit Racing. Items marked with an asterisk are optional, meaning stock parts can be substituted.
|GM Performance Parts|
|PN 12558060||Vortec head assembly||$579.90|
|PN 12495491||Heavy-Duty pushrods (16)||*$42.95|
|PN 12499223||Gasket set||$96.95|
|PN 12495499||Head bolt set||$28.95|
|PN 25534359||Circle track valve covers||*$114.95|
|PN 25534355||Valve cover breathers||*$38.95|
|PN 12338092||Valve cover bolts (8)||$15.60|
|PN 12550027||Intake bolts (8)||$23.04|
|PN 12495490||1.5:1 self-aligning rocker arm kit||$56.95|
|PN FEL1094||0.015-inch compressed head shims (2)||$43.76|
|PN 60103LK||Voodoo 268 cam &lifter set||$185.95|
|PN 93117||Double roller timing chain||$43.10|
|PN 74818LUN||Beehive ovate springs (16)||$167.58|
|PN 75787LUN||7-degree spring retainers (16)||$55.01|
|PN 85340LUN||1.5:1 self-aligning roller rocker arm kit||$338.10|
|PN PP52033||Hurricane Vortec manifold||$172.99|
|PN 8502||Air Strike Vortec manifold||$217.88|
|TOTAL||With stamped steel rockers||$1666.63|
|With roller rockers||$1947.78|
|Engine||Test 1||Test 2||Test 3||Test 4|
Test 1: Baseline GMPP 290hp 350 crate engine, GMPP firstname.lastname@example.org, .450/.460 lift camshaft, Weiand Action Plus manifold, Holley 4779 double-pumper carb, 34 degrees ignition timing, 13/4-inch long-tube headers
Test 2: Lunati Voodoo 227/233 @ 0.050, .489/.504 camshaft, Weiand Air Strike Vortec intake, 1/2-inch phenolic carb spacer, Holley 4779 Double Pumper carb, 36 degrees ignition timing, 13/4-inch long-tube headers
Test 3: Same as Test 2 but with Lunati 1.5:1 roller rockers
Test 4: Same as Test 3, but with Professional Products Hurricane Vortec intake manifold, 1/2-inch phenolic spacer, 37 degrees ignition timing Peak Values are in bold.