Throughout the annals of time, great things happened when famous names joined forces in a combined effort: Hewlett-Packard in industry, Holman-Moody in racing, and now Musi-Holley with 450 hp in a crate. Until now, only carburetor fans were able to enjoy this easy power since the complexity and required calibration of an EFI system left no takers in the mail-order-motor foray.
The Musi-Holley crate engine is a 383ci stroker featuring the advanced Commander 950 EFI system. Though advertised as a 450hp package, our subject 383 produced slightly more when PHR visted Musi's shop in Carteret, New Jersey. The focus of the project was to combine the EFI technology of Holley with the engine building prowess of Pat Musi. The results are impressive by anyone's standards; 450 hp and 450 lb-ft torque, with a curve that is as flat as Kansas. This is accomplished on 92-octane pump gas with the reliability of an anvil. Designed as a street/strip package, the Musi-Holley engine will see use in everything from restored musclecars to tow vehicles. PHR was given the exclusive story on this breakthrough engine and is proud to offer the following analysis.
If the mantra of the real estate industry is "location, location, location," then the chant of the EFI world is calibration in triplicate. The calibration will make or break an EFI system and has been the reasoning behind the lack of EFI crate motors. All too often, the end user would be wooed into thinking that because an aftermarket ECU was programmable, the process of calibrating the spark and fuel tables would be as easy as jetting a carburetor and recurving a distributor. It was then discovered that a wealth of experience, equipment, and time was required to successfully accomplish this. What Pat Musi did was remove the variables, offering a fully calibrated, high-performance EFI engine ready to be installed in a vehicle. The process was not as simple as it sounds though; the engine needs to be designed around EFI. Musi spent more than one year sorting components to achieve the desired results. He worked with Holley engineers and EFI calibration wizard Julio Hormilla of Cartek, Inc. One of the key elements to the success of this project was Musi's research and development facility, which includes an advanced DTS dyno and a complete data acquisition system. Parameters such as air/fuel ratio, using an integral wide-band linear air/fuel meter and brake-specific fuel consumption (BSFC) data, were all necessary to produce these results. BSFC data is required to determine how efficiently an engine converts fuel into horsepower. Measured in pounds of fuel, this measurement is common on dynos equipped to test engines using a carburetor, but it is a much more complicated procedure with EFI.
An EFI system pumps more fuel than it uses and returns the rest. To calculate BSFC, the fuel returned needs to be subtracted from the fuel pumped. This necessitates the use of expensive flow meters and software to do the math. Musi's efforts were rewarded with a BSFC rating of 0.386 at peak torque (less than 1/2 pound of fuel to produce 1 hp), which is approximately 29 percent more fuel efficient than a carburetor would be, given the same engine package.
A concern beyond fuel efficiency is octane tolerance, which is defined as the engine's ability to resist abnormal combustion with low-grade fuel. To this cause, Musi enlisted mechanical design theories and the advanced Holley Commander 950 electronics. In contrast to a traditional stroker engine package, Musi uses a longer 6-inch, center-to-center, I-beam-style 4340 connecting rod, instead of a standard 5.700-inch or 5.850-inch for a 350 and 400, respectively. When paired with a stroke of 3.750 inches from the nodular one-piece, rear-main-seal crankshaft, the Musi package yields a rod/stroke (R/S) ratio of 1.6. When the R/S ratio goes numerically higher, piston side loads decrease, reducing motoring friction and thrust-side bore wear. This is effective in unleashing power while adding engine life.
Additionally, the piston will dwell longer at TDC when measured in crankshaft rotational degrees. This keeps the combustion region longer in the crankshafts arc of rotation, fighting detonation and allowing cylinder pressure to peak higher before the piston starts to move downward in the bore. Octane tolerance is improved with a higher numerical R/S ratio, since the smaller combustion region does not allow an additional flame front to form. The use of a feedback timing control (knock sensor) system in the Commander 950 then allows the spark table to be brought closer to the spark-knock-zone without entering it. If the fuel quality is less than desirable, an integral knock sensor retards spark timing to prevent detonation and will automatically return to the Musi advance curve when conditions allow.
The Holley aluminum cylinder head incorporates a 20-degree valve angle from vertical, instead of the conventional small-clock Chevy's 23-degree design. This rolls the valve over more on its side and provides a more efficient flow path from the port of the cylinder head to the combustion chamber. The combustion chamber design is considered a quick-burn style with an idealized spark plug location and a large squish pad to induce in-cylinder charge motion. This along with the forged piston design allows for a 10:1 compression ratio under sustained engine loads on 92-octane fuel. Manley 2.02- and 1.60-inch high-flow valves are installed and Musi's team of experienced machinists preps each cylinder head for the most effective valve seat angles and spring pressures.
All the technology in the world would be useless if the engine didn't stay together, so a brand-new, four-bolt GM 350 block is used for the 383 package. The block is then machined by Musi and modified for the additional stroke and longer connecting rod. The procedures include magnafluxing for quality control, decking, line honing, and complete blue printing to Musi's own specs. The rotating assembly is balanced and a Lunati hydraulic roller camshaft of undisclosed specifications is used. Rounding out the valvetrain are Lunati 1.6 roller rockers and lifters, along with beautiful aluminum Pat Musi/Holley valve covers.
SEEING IS BELIEVING
When PHR arrived at Musi's shop, a complete 383 was mounted on the dyno and waiting to be put through its paces. With Pat at the controls, it fired immediately and ran smoothly when cold, without having to be fast idled. The idle quality was smooth, and the engine produced strong vacuum, indicating that power brakes and other vacuum-driven accessories would work well with the 383. The dyno console revealed a perfect air/fuel ratio of 14.7:1 at idle and light load, and the engine produced a smooth precision sound that is music to the ears.
Throttle response with the 6-inch rod and Commander 950 EFI system was instant, and at full bore the engine sounded every bit of the 454 hp the dyno pull stated. Offered as a complete package for $8,995, the Musi/Holley 383 is a very impressive piece. Early indications suggest there will be many of them on the road and at a dragstrips. The small-block offers power, torque, fuel economy, and excellent driveability. As we said in the beginning, good things happen when two great names get together. Did you expect anything else?
Bigger is Better
What can be better than a 450 horsepower Musi/Holley small block? A 625hp 540ci Musi/Holley big-block! Not wanting big-block fans to be left out, the same effort has gone into producing a mail-order EFI 540 that runs on pump gas and follows the turnkey logic of it's smaller brother. Featuring a new Merlin II block and ported cylinder heads, this hydraulic roller cam package is designed for years of low maintenance motoring. Sporting 10:1 compression and the benefits of Commander 950 EFI, 640 lb-ft of torque is a only a phone call away. The complete package is $16,999, and can be delivered to your door with everything you need except the vehicle to put it in.
NEW MUSI/HOLLEY DRY FLOW NITROUS
Adding nitrous to an EFI engine has been met with mixed reviews. There has always been a debate raging over where to introduce the artificial aspiration. Until now two schools of thought prevailed: wet and dry.
Wet systems add nitrous and fuel together prior to flowing the course the runners of the intake manifold. Opponents of this design state that EFI intake systems were designed to carry only air, not air and fuel, thus creating distribution problems. The dry flow system eliminated the fuel, relying on the EFI computer to calculate fuel enrichment based on temperature change at the MAF sensor. A plate was required between the throttle body and intake manifold to introduce the juice. Realizing there had to be a better way, Pat Musi designed a dry-flow throttle body for both the Commander 950 and GM TPI and LT1 systems. It's such a simple approach, one can only wonder why it took so long to be invented. Musi redesigned the throttle body to incorporate nitrous discharge holes after the throttle plate. Since the nitrous will be a gas when it enters the plenum of the intake manifold, distribution is not a concern. The Commander 950 then controls the enrichment and spark retard automatically, making for not only a clean, trouble-free installation, but also a stealth appearance. Designed by Musi and manufactured by Holley, the new dry flow system will be available by the time you read this.
The bottom of the bore needs...
The bottom of the bore needs to be clearanced for the longer stroke and connecting rods.
The Holley 20-degree cylinder...
The Holley 20-degree cylinder heads are a key component of this engine package.
A heart-shaped combustion...
A heart-shaped combustion chamber offers a high level of octane tolerance.
The Holley Commander 950 kit...
The Holley Commander 950 kit includes everything you need to fuel-inject any vehicle. The Commander 950 ECU controls both spark and fuel and is one of the most advanced aftermarket EFI controllers available.
EFI guru Julio Hormilla and...
EFI guru Julio Hormilla and Pat Musi discuss a calibration change. It took more than one year to develop and refine the 383.
The nitrous inconspicuously...
The nitrous inconspicuously enters the front of the Musi/Holley dry-flow throttle body.
The nitrous is discharged...
The nitrous is discharged in gas form under the throttle plates through eight orifices.
A dry-flow, nitrous throttle...
A dry-flow, nitrous throttle body is offered for LT1 and TPI applications also.
This style uses one large...
This style uses one large nitrous discharge hole for each throttle plate.