LT1 Engine Build - Late-Model 383 Buildup The Finale

Here we go! Our 383 stroker gets loaded onto the dyno cart at Vrbancic Brothers Racing. At this point everything is in place except the headers and Speed-Pro electrical connections. The large aluminum bracket at the front of the engine was custom made to hold the water-to-air intercooler that the guys at ATI sent special for the dyno runs.

Here we go! Our 383 stroker gets loaded onto the dyno cart at Vrbancic Brothers Racing. At

Seven-hundred horsepower? From a late-model computer-controlled engine? Are you guys crazy? And you want to drive it where? On the street? On pump gas? Good Luck!

We all make goals. It's what carries us on in life. We aim for that bigger paycheck, strive to lose an extra pound or two, or plan for that house in the country with a big yard for the kids to play in (or a garage for us to play in). We would become pretty complacent if we didn't keep reaching for the seemingly unreachable. So when it came to designing the ultimate late-model street powerplant, we had some goals, too. Three to be exact: 700 horsepower, 600 foot-pounds of torque, and a powerband that would enable us to use this potent package on the street-realistically! Did we attain them, you wonder? Keep reading...

To refresh your memory about this project: Our intention when we hooked up with Frank Beck at Beck Racing Engines in Phoenix, Arizona, was to build a late-model LT1 using the best parts available to create a bulletproof, high-power street engine. To begin with, we had a factory block converted to four-bolt mains and had it meticulously machined to accept a set of oversize SRP forged slugs and a stroked Cola steel crankshaft. To be sure that our reciprocating assembly was up to the task of handling 700 ponies, we added a set of Manley H-beam connecting rods, a Titan Sportsman adjustable oil pump housed in an extra-capacity Billet Fabrication aluminum oil pan, Crane valvetrain components, and surefire ARP fasteners throughout.

This is the McLeod billet steel flywheel. Note the studs for the dual-disc setup. Here the dyno's link is matched up with the flywheel's bolt circle.

This is the McLeod billet steel flywheel. Note the studs for the dual-disc setup. Here the

Once we had assembled the components for a solid short-block, we turned our attention to the induction side of things. First, we chose to use a set of replacement cylinder heads from Airflow Research. The aluminum big-valve (2.05-inch intake, 1.60-inch exhaust) castings have a tremendous flow capacity (both before and after BRE massaged them with a die-grinder) on both the intake and exhaust sides, and they retain the factory's reverse-flow cooling technology. Feeding the "pump" is an Arizona Speed and Marine reworked LT1 EFI direct-port intake manifold that has been Extrude-honed and modified for later use with nitrous oxide injection, and a well-machined billet 58mm throttle body.

Injectors are MSD high-flow, high-pressure units that are fed fuel via a boost-referenced fuel regulator and high-pressure fuel pump from Aeromotive Systems. A Speed-Pro C-Com engine management system from Federal-Mogul makes it all work in harmony (and can be tuned for maximum power using a PC). GM Performance Parts provided the majority of the supporting items, such as fuel rails, a water pump, the Opti-spark ignition system, a timing cover, etc. ATI sent us one of their super Super Dampers, Tilton fired off a small-yet-powerful starter motor, Carbon Components carbon fiber valve covers beautifully hide the roller rockers, and McLeod furnished a nicely machined, heavy-duty flywheel and clutch assembly. To say that this bad boy is going to hook up is most definitely an understatement.

But the biggest part of the equation in our quest for 700 horses is the addition of the D-1 Procharger from Accessible Technologies. The D-1, which is a step up from the company's entry-level P600b unit, flows roughly 25 percent more than it-and also has a higher peak efficiency, the trade-off being the flatness of the boost curve (the D-1 is peakier). Typically, the engineers at Procharger don't recommend using the P600b on anything making much more than 650 hp (max), whereas the D-1 works nicely up to and above 850 ponies, which was perfect for this project.

Machining and long-block assembly were done at BRE's Phoenix shop, while all of the peripheral add-ons were installed by your dedicated staff at Super Chevy. Once the basic engine was together, we put it in the bed of a small truck and headed toward Vrbancic Brothers Racing and their state-of-the-art DTS dyno facility to see where we stood on the horsepower curve.

Here George Vrbancic adjusts the throttle cable from the dyno to the Arizona Speed & Marine billet throttle body. Since most of the dyno tests that the Vrbancics do are with carburetors rather than fuel injection, a few adjustments were necessary in order to make sure that the throttle blades opened all the way.

Here George Vrbancic adjusts the throttle cable from the dyno to the Arizona Speed & Marin

In the previous three parts to this story, we've focused on making sure the sum of all of the trick parts added up to one cool late-model stroker engine. While we're sure that all of the trick parts went together flawlessly, there's only one thing that really matters, and that's how she does on the dyno.

Making The Numbers!
Making an electronic, fuel-injected small-block spin the dyno needles into the upper horsepower and torque stratosphere is no small feat, to say the least. To do so required the special talents of both man and machine. To manage the 383's fuel and spark delivery, we employed the aforementioned C-Com engine computer. To manage the C-Com, we got help from one of the country's premier electronic tuners, Craig Railsback of BDS Blowers. Craig joined us with his laptop PC for two sessions and had our modern LT1 running virtually right on target with little effort.

Our goal on the dyno was to learn three things: How much power and torque will the engine make normally aspirated on pump gas; how much with the D-1 Procharger on 92 octane; and, for bragging rights, how much power we can make with the D-1 on racing fuel.

After meeting all three parameters, the first conclusion we made was that this combination of parts was perfect for a street engine. Despite the high-flow cylinder heads, our 383 stroker did not make any additional power after 6,000 rpm (probably due to the limited flow capacity of the stock-style LT1 intake). Essentially, on all three trials, the mighty mouse was screaming that its power was done at six-grand! But, as a tribute to how well matched this combination was, the power and torque curves were excellent, with peak numbers in all tests within a couple of hundred rpm of one another. And, with boost, the torque came on immediately and never fell off, all the way to redline.

So, you're probably wondering at this point what those magic numbers are. What was our goal originally? First, it was to make 700 ponies on good gas. Second, we wanted enough torque to get our not-so-lightweight '96 Camaro convertible up and running-in a hurry. With 110-octane racing fuel, our 383 hit unbelievable numbers of 735 horsepower and 693 foot-pounds of torque! And as far as those numbers being in a usable rpm range, power peaked at 5,600 rpm, while the top torque mark wasn't too far behind at 5,500 rpm. The torque curve was more like a table top on the graph, though, as the engine made more than 500 foot-pounds at 3,000 rpm and never dropped below 680 through shutoff.

The D-1 Procharger requires a special-built bracket arrangement to fit in the snug confines of a late-model F-body's engine bay. Despite its custom look, this setup was first-class. Note also the MSD large-diameter plug wires coming from the LT1's factory Optispark ignition.

The D-1 Procharger requires a special-built bracket arrangement to fit in the snug confine

We know what you're thinking at this point. With high-octane fuel, we got aggressive with the ignition timing. Not so! In fact, the timing was ultra conservative, according to Craig, at around 36 degrees, while maximum boost was just a hair over 10 psi. Everything worked perfectly during this session, which led us to come back and run the engine on pump gas both off boost and with the blower belt on.

With Unocal 92-octane premium unleaded being pushed through the Aeromotive Systems electric pump at a maximum of 65 psi, we ran a baseline test of the engine without running the blower, just to see how stout this 383 was. Now, considering that the compression of this engine was down to around 9.4:1 to allow for the additional boost, and add in the fact that the 72-pound injectors were designed more for a supercharged application, we weren't sure just what kind of numbers to expect. What we got was a pretty stout non-blown engine, with a maximum of 422 horses (5,600 rpm) and 420 ft-lbs of torque (5,000 rpm). This was with 42 degrees of total timing and a running temperature of 212 degrees F.

Doing the math at this stage tells us that we gained a whopping 313 horsepower and 273 foot-pounds of torque with good gas and 10 pounds of boost! Simply incredible.

The Arizona Speed & Marine throttle body came with a throttle position sensor in place. All we had to do was connect the correct wire and make sure that the unit had the correct voltage reading.

The Arizona Speed & Marine throttle body came with a throttle position sensor in place. Al

But what about the real test? Pump gas on boost. Well, we were not disappointed, especially since we had to back the timing way down from what it was with the high-octane fuel (from 36 degrees to 28). Despite the loss of timing, the difference in horsepower and torque readings between good gas and pump gas measured only a slight loss of 6.6 percent in horsepower and a minute 3.2 percent drop in torque. That meant that our street-worthy 383 stroker has a legitimate 686 ponies and 671 ft-lbs of torque on tap, on drive-through 92-octane junk fuel.

As for drivability, the peak horse reading was at 5,700, which is where the dyno stopped the test (yup, it was still climbing), while torque peaked at a tractor-like 4,900rpm. This engine, with a maximum of 9.7 pounds of boost, made 504 ft-lbs of torque at 3,100 and was still making 634 ft-lbs at 5,700 when we shut her down. And, the temperature needle never got hotter than 212 degrees F (which is about normal for late-model reverse-cooling LT1s).

Here, EFI tuning wizard and BDS main man Craig Railsback makes an adjustment to the throttle prior to firing up the engine.

Here, EFI tuning wizard and BDS main man Craig Railsback makes an adjustment to the thrott

In summary, this engine may have more horsepower than most of us will ever be able to use on the street. But, for the cost of good parts and the ATI D-1 Procharger, you can have a bona fide 700-horse street engine that is tame enough to sit in traffic or wild enough to propel its nearly two-ton carriage down the quarter-mile in the 10-second zone. That part of our project still remains to be seen. But stay tuned-in the coming months we will attempt to swap out our donor car's original low-mileage LT1 and stab in this potent 383 stroker in its place.

Hot Box
I'm a hot rodder to the core, but as most of you know, my roots are in high-winding small-blocks with carburetors and solid-lifter roller cams, not electronics and fuel injection. I don't profess to know a lot about the computer controllers that can wring out the most power from today's EFI machines. Sequential port fuel injection; bank-to-bank firing, individual cylinder timing. It all sounds like space-age jargon to me. But with the help of BDS's Craig Railsback and the Federal-Mogul Speed-Pro C-Com electronic engine management control system, I'm learning.

The MSD HVC coil is designed to throw a lot of voltage at the ignition system. We used this coil in conjunction with their Digital 7 Plus ignition box and had more than enough fire to light the plugs.

The MSD HVC coil is designed to throw a lot of voltage at the ignition system. We used thi

First, the C-Com software is designed for those wishing to have the most control over their EFI machines. It's designed for competition, not to circumvent the factory OBD-11 computer for street use. The C-Com allows the engine tuner to choose what sort of fuel-injection control best suits the conditions. Two systems are available.

First, for most applications, the Bank-To-Bank system is perfect. This controller fires half of the engine's injectors each 180 degrees of crankshaft rotation. This gives the engine improved fuel delivery and performance, and, for street applications, better driveability. This system is ideal for converting an engine from a carburetor to EFI. Other items that this system can control are the idle air, fan, fuel pump, single-stage nitrous, and program knock retard. A wide-band O2 sensor for closed-loop can also be used. And, it can be upgraded to the Sequential system, if the need arises.

The Sequential Electronic Fuel Injection system was designed for the ultimate in power production and tuning. It uses technology that will individually fire each injector for optimizing fuel delivery. It can also be equipped with options that allow for individual cylinder fuel/timing, and will facilitate adding a two-stage nitrous setup.

Both systems can be individually programmed by using a PC-based (386 and higher) laptop computer. With this capacity, you can literally program the engine to recognize the special needs of specific cams, superchargers, compression ratios, etc.

In our case, we were able to tell the engine that it needed to have driveability as well as maximum power output. And, when the 383 finds its way into the Camaro's engine bay, if the need arises to add a little more fuel or back the timing off, our PC won't be too far away.