Big Wind Blowing

When the Vortec 350 truck engine was introduced in 1996, it represented the pinnacle of cheap but efficient horsepower from the venerable small-block Chevy engine family. Revised cylinder heads with fast-burn combustion chambers and trick intake runners meant wringing every last drop of torque from the aging small-block architecture. And even though the new LS1 Gen III engine would get rave reviews in the ensuing years, it was the innocuous Vortec that quietly piled up by the millions in salvage yards and Internet auctions across the country.

The Vortec 350 can make prodigious amounts of horsepower on the cheap, and a low-buck blower kit like the 142 from Weiand can take that to the extreme on a thrifty nickel. The folks at Weiand took their famous 144 Supercharger kit, designed a proprietary intake manifold for the Vortec heads, and then cut the cost of the rotor assembly to make it more affordable. This also happens to improve longevity, as the 142 compressor design eliminates the 144's Teflon rotor tips.

Here's the meat of the deal: for a hair over $2,200-the street price of a basic Weiand 142 blower kit-you can add 130 hp to a Vortec 350 V-8. (Pricing gets a little complicated when you consider that all Vortecs were fuel-injected engines from the factory and this is carbureted). For our dyno test, we used a GM Performance Parts 350 HO partial long-block, which includes factory iron Vortec heads, cam, lifters, and valvetrain. You'd do just as well, though, to get a salvage motor, as it already includes the hydraulic roller lifters and cam (the 350 HO only comes with flat-tappet hydraulic lifters). Since Weiand is part of the same group as Holley and Lunati, our test engine has the upgraded hydraulic roller cam, pushrods, lifters, and valvesprings.

Test Engine

Instead of a used truck engine, we started with a 350 HO partial crate engine from GM Performance Parts (PN 12486041). This brand-new crate engine is a 350ci partial assembly equipped with Vortec heads, a four-bolt main block, and 9.1:1 compression. It costs about $2,500, and is rated at 330 hp at 5,000 rpm and 380 ft-lb at 3,800 rpm, using a very un-Vortec-like flat-tappet cam. We topped this engine with a Weiand 142 supercharger and a small Lunati roller camshaft, and made the required improvements to the valvetrain to keep things stable. The results are impressive at a conservative 5 psi of boost, and the cost is minimal in comparison. Some parts, like the Jesel beltdrive, are not required, but make cam changes on the dyno much easier (which is why we didn't include them in our estimated cost).

Special Ignition Needs

The cost chart does, however, include a boost-retard ignition from MSD, which you'll want. (Our DTS dyno cell was already equipped with a high-end ignition with boost retard capability.) When using pump gas, it's typically necessary to retard the ignition timing as a function of boost, and the MSD 6-BTM allows you to adjust that rate with a dial right from the cockpit. In a naturally aspirated engine, the ignition spark is timed optimally to produce maximum cylinder pressure a few degrees into the power stroke, but the same timing curve can cause a premature pressure rise in the combustion chamber if the timing is not retarded under boost. This phenomenon is called detonation, and is easily rectified by subtracting timing from the cumulative advance (base plus mechanical), in proportion to boost pressure. A hotter spark is also a good idea, as the density of the air/fuel charge is greater. Beyond that, a slightly colder plug with a wider gap is a good bet.

Carburetion

The test carb on our Vortec 350 is a 700-cfm mechanical secondary Holley (PN 510-0-80572S), which is specially calibrated with a fuel curve for a roots blower like the 142. On this blower-specific piece, the power valve channel is blocked off underneath-otherwise it would remain open all the time, letting fuel in. Instead of taking its reference signal above the blower inlet, the power valve reference comes from an external line on the carb's main body; a reference line, typically a vacuum hose, attaches to a nipple on the blower manifold. The Holley blower carbs have been calibrated for the blower kits and, as we found, the fuel curves are pretty close right out of the box.

Valve Timing

With a stock hydraulic roller-cam truck motor, we might've thrown on higher ratio rockers and called it a day-but the crate motor's mild 212/222-at-.050 flat-tappet cam (.435/.460 lift) was far from optimal. We replaced it with a more boost-friendly 215/218 hydraulic roller, which had greater lift (.489/.503) and a wider lobe separation angle for better boost containment. A typical performance cam with overlap allows boost and unburned fuel to pass directly out of the exhaust, which can kill fun in a hurry. The Lunati roller we swapped in has enough duration to keep things on the boil, but has a small enough overlap (115-degree LSA) to trap the boost and fuel in the combustion chamber. In support of this, a set of roller-guided 1.5 Crane Gold rockers was added, along with hardened Bracket Master II pushrods (7.200-inch) and Lunati hydraulic roller lifters. The stock Vortec valvesprings reach their limit well before .500-inch lift, so upgraded Lunati valvesprings (PN 638-73943) were introduced to stabilize the valvetrain.

On the Dyno

A DTS dyno is our yardstick of choice when it comes to anything bound for the street. The power absorber on the DTS is capable of pulling all the way down to 2,500 rpm, which might not matter much to a racer, but can really make the difference for a street car. The Weiand 142 is a street piece all the way, so we wanted to verify what we've felt by the seat of our pants. After a few ignition and jetting tweaks, the butterflies on our Holley double-pumper were opened in earnest. Sure enough, the Weiand 142 started cranking right off the bat, with 438 ft-lb coming on at 2,500 rpm, and peaking at 479 ft-lb at 3,800 rpm. Power peaked at 460 hp (5,900 rpm), and seemed unfazed by the diet of 93 octane pump gas.

How Much Is It?

The cost chart with line-item breakdown totals $6,960.90 for this combo, using typical mail-order pricing. It does not include gaskets, since the partial engine assembly comes with them and the Weiand kit has most of the rest. Our dyno already had the ignition system and water pump, so those aren't on the chart either. Our focus here is on the blower and ancillary items, not the engine itself. Nevertheless, the GMPP 350 HO long-block is a good place to start, though judicious use of eBay can score a great Vortec truck core for a lot less than $2,500. The best thing about a used late-model, fuel-injected, computer-controlled engine (such as the '96-'02 Vortec 5700 truck engine, RPO L31) is that they suffer minimal wear thanks to typically better production tolerances, superior lubrication, and much less ring wash on start-up. A good serviceable L31 Vortec core goes for about $300 to $400 from a reputable core supplier like AA Midwest (800-426-7881). A new set of rings and bearings with a pass from a berry-bush hone on an electric drill will do the trick if you're strapped for cash. Realistically, you could take another $1,500 out of our total cost and not suffer any undue consequences.

Quick Tips

Weiand 142 Supercharger Kit

*The 142 supercharger is named so because it displaces 142 ci of air per revolution of its rotor blades. It is also the smallest blower Weiand makes. According to Holley's Matt Held, "It's like taking your existing cubic-inch displacement and adding another 142 ci to it. The original design goes back to the '80s, except nobody was making an intake manifold to work with the Vortec heads, which have a different intake runner shape and different bolt locations."

*Weiand built the 142 blower kit specifically for the Vortec 350 and its crate-engine variants. Many of these are in the 8.6 to 9.5 compression ratio range, which is ideal for such a blower. The pulleys in the 142 kit (and all other Weiand blower kits) are matched to give the proper drive ratio to avoid engine damage.

*Matt at Holley says, "If you start out with a 9:1 engine and you add 5 pounds of boost to it, you'll be pushing around 12:1 compression, which is right at the limit of pump gas. That's the way the kit is set up right out of the box. This is for a typical small-block of 350 to 360 inches. If you were to take this same kit and drop it on a 383 or a 400, your boost will go down; if it goes on a 302, 305, or 307, your boost is going to go up."

*Any time you're going up on full boost, you're going to need a boost-retard ignition. The MSD Boost retard works great, and you can set it at 1, 2, or 3 degrees of ignition retard per pound of boost.

*The difference between the classic 144 blower kit and the 142 blower shown here is in the rotors. The 144 has Teflon-tipped rotors, which initially generate a better seal because they have a higher tolerance. Eventually, though, the rotor strips wear and need replacing. On the other hand, the 142 rotors are designed to ride against the case with a gauged clearance, and never need refurbishing.

Where The Money Went

Dts Dyno Results

Weiand 142 Supercharger GM 350 HO Crate Motor

Sources

ACCEL Ignition

216-688-8300

www.accel-ignition.com

Holley/Lunati/Weiand

270-781-9741 (Lunati: 662-892-1500)

www.holley.com

Jeg's High Performance

800-345-4545

www.jegs.com

MSD Ignition

915-855-7123

www.msdignition.com

Scoggin-Dickey Parts Center

800-456-0211

www.sdparts.com