Supercharged Crate Engine - A Crate Start

Ever wished someone offered an affordable supercharged small-block crate motor? The experts at Jegs and Vortech have just what you're looking for.

Ever wished someone offered an affordable supercharged small-block crate motor? The expert

Here at Super Chevy, we are often spoiled when it comes to engine buildups. With so much hardware at our disposal, we sometimes forget about what happens out there in the real world. Getting to build or even just cover the buildup of 800hp, 900hp or even 1000hp small- and big-block Chevys has a way of distorting your performance reality.

While 1000hp turbo small- and big-blocks may be commonplace in the dyno cell, the reality is that they are few and far between out on the streets. The chance of running across one of these killer machines on your daily commute is about as likely as having Paris Hilton stroll up to buy you a drink. On the other hand, the odds of that Camaro, Chevelle or even late-model truck sporting a run-of-the-mill crate engine are a lot more grounded in the real world.

Staring with the 260hp 350 Jegs/GM crate engine helped keep cost to a minimum while providing a solid foundation for future improvements.

Staring with the 260hp 350 Jegs/GM crate engine helped keep cost to a minimum while provid

While we all long for the big-power buildups, the reality is that most engine bays are filled with the stock stuff. Given the intended usage, the stock or mild crate motors are an ideal choice for vehicles whose only race is the daily commute, a Friday night gamblers race at the local strip or lugging that heavy load from the local Home Depot. Even if performance is high on the wish list, speed always costs money. This is true even of the venerable small-block Chevy, as complete high-performance engine assemblies can easily exceed $10,000. Since none of us are made of money, cost is always a huge consideration when it comes time for a buildup.

Affordable performance is exactly why Jegs and Vortech got together to bring you this supercharged crate motor (priced under $5,500). The idea was to provide a combination that was both powerful and affordable, while simultaneously offering the ability for future upgrades. The affordable portion of the equation came in the form of the most cost-effective motor available. Naturally the low-cost GM Parts 260hp crate engine was hardly a powerhouse, but the cure for the power portion of the equation came from Vortech in the form of their carbureted small-block supercharger assembly. What made this assembly so attractive is the fact that it was available complete and ready to run with all of the potential installation and tuning problems already addressed.

Upgrades to the basic crate motor included a dual-plane Edelbrock Performer aluminum intake manifold.

Upgrades to the basic crate motor included a dual-plane Edelbrock Performer aluminum intak

The 260hp 350 small-block features a 4-bolt block stuffed with a cast crank, powdered metal (LT1/LT4) connecting rods and cast pistons. The dished pistons combined with 76cc chamber, cast-iron heads to produce a very blower-friendly static compression ratio of 8.5:1. In other words, this low compression ratio was just begging for some boost. The iron heads also featured 1.94 intake and 1.50 exhaust valves, which receive lift from a mild hydraulic flat-tappet cam. The cam offered a .383/.401 lift split and a 112 lobe separation. The mild cam profile was one of the reasons the 350-cubic-inch crate motor was rated at just 260 hp (with a small 4-barrel carb and headers).

Additional features included provisions for both right- and left-hand dipsticks, a 4-quart oil pan and timing tabs for both 6.75 and 8-inch balancers. Basically, the inexpensive small-block was an excellent cost-effective starting point for a more serious buildup. What the thing needed now was some more power.

Quick Fuel supplied a 650-cfm four-barrel carb designed specifically for the supercharged small block.

Quick Fuel supplied a 650-cfm four-barrel carb designed specifically for the supercharged

That additional power came in the form of a Vortech supercharger, but not until a few upgrades were made to the small-block. As indicated previously, the idea behind this was to provide a complete assembly that was ready to install with a minimum of expenses and associated hassles. While the 350 was a decent starting point, there were still a few things necessary to complete the package before getting to the blower. Included in the upgrade was an intake, carb and HEI distributor.

Also included was a mechanical fuel pump, damper and the associated gaskets necessary to complete the installation of the induction system. According to Jegs, the supercharged EZ crate motor will be available without the distributor, damper and other accessories for enthusiasts wishing to replace an existing motor. Jegs will then offer these accessories as a package for those wanting a complete supercharged crate motor.

The kit included dedicated fuel lines for the dual-feed carburetor.

While Jegs offers these upgrades with their standard GM crate motors, there were a few changes necessary to suit the needs of the supercharged combination. The Edelbrock Performer intake manifold was retained, as were the necessary intake gaskets, but the carburetor was upgraded to a 650-cfm unit from Quick Fuel designed to meet the fuel flow requirements under boost. When combined with the boost-referenced fuel pump, the combination ensured adequate fuel pressure to the carb under boost. The carb jetting in the 650 was naturally optimized for the boosted application.

The power producer of the new blown crate motor was, of course, the supercharger system itself. Designed by Vortech, this V-2 S-trim centrifugal supercharger was designed to provide roughly 7 psi of non-intercooled boost to the 350. Naturally, a great deal more boost, and therefore power, are available from the Vortech (we've easily exceeded 600 hp with this kit on wilder combinations); but for this application, the pulley ratios were kept purposely conservative to keep boost down.

A manual (marine) fuel pump was employed on the blower motor. Note the vacuum/boost reference fitting designed to always provide 7 psi of fuel pressure on top of the existing boost pressure.

A manual (marine) fuel pump was employed on the blower motor. Note the vacuum/boost refere

To establish a baseline for this story, we first ran the combination in normally aspirated trim. This allowed us to demonstrate the merits of the supercharger, as the power gains will always be a percentage of the original power output. After installing a small 4-barrel carb (the Quick Fuel 650-cfm carb was jetted for boosted applications) and headers, the 260hp crate motor responded by thumping out 264 hp at 4400 rpm and 353 lb-ft of torque at just 3500 rpm. No surprises here, as the mild cam, compression and head flow limited the power output of the 350 small-block.

Adding the Vortech blower to the mix increased the power output of the 350 to 383 hp at 5500 rpm and 431 lb-ft of torque at 4200 rpm. The Vortech improved the power output of the motor by 45 percent with just over 7 psi of boost.

Upgrades to the basic crate engine also included an HEI distributor. If we could ask Jegs for one thing, we'd like to see a small cap distributor to improve clearance with the carb enclosure.

Upgrades to the basic crate engine also included an HEI distributor. If we could ask Jegs

Blower and crate engine fans alike should rejoice in this new offering from Jegs, as the combination is both affordable and strong, with plenty of power left in reserve. Every bit as important is the fact that the new combination comes complete and ready to install. We liked the look of the combination, but, being enthusiasts, we can't wait to ditch the wimpy hydraulic flat-tappet cam and factory iron heads in favor of more performance-oriented pieces.

Given the way small-blocks respond to improvements in breathing, we look for some serious power gains from the proposed head and cam upgrade. What makes the heads and cam even more appealing is that the power gains offered by the additional breathing will actually be multiplied by the boost pressure. If we got a 45 percent gain from 7 psi of boost with the 264hp combination, we expect to see a similar gain once we get the normally aspirated motor up closer to 350 hp. Remember, every good supercharged powerplant starts with an equally good normally aspirated one.

Priced at under $5,500, this Jegs supercharged crate motor combination is almost like buying a Vortech supercharger kit and getting the long-block for free.

Naturally Aspirated 260hp 350:
As is evident from the graph, the Jegs/GM crate motor was designed more with economy in mind than maximum power. Rated at 260 flywheel horsepower, adding a small Quick Fuel carb, Edelbrock Performer intake and HEI distributor allowed the 350 small-block to produce peak numbers of 264 hp and 353 lb-ft of torque. The low-budget normally aspirated crate motor was equipped with a 4-bolt main block, LT1 PM rods and cast pistons (all new parts, by the way, not remanufactured).

Jegs/Vortech Supercharged 350:
As expected, adding the Vortech supercharger dramatically improved the power output. The peak numbers jumped from 264 hp and 353 lb-ft of torque to 383 hp and 431 lb-ft of torque at just over 7 psi of boost. The efficient Vortech supercharger improved the power production of the crate motor by an impressive 45 percent. Even more important is the fact that this supercharged 350 comes complete and ready to run.