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Edelbrock Pat Musi 555ci Crate Engine - Joint VentureEdelbrock Teams Up With Pro Street Legend, Pat Musi, To Bring A 555ci Crate Engine To Your Doorstep. From the April, 2010 issue of Popular Hot Rodding By Michael Galimi Photography by Johnny Hunkins, Michael Galimi, Robert McGaffin
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Over the years, Edelbrock has been known for its high-quality cylinder heads and intake manifolds, but as the company has grown older, it has diversified its lineup of go-fast components. In the past few years we have watched the Fun Team jump into the nitrous market, suspension components, and even superchargers for various applications. Its latest venture has been crate engines. This month, we poke and prod at one the company's most popular bullets, an Edelbrock Pat Musi 555ci Crate Engine that spun the dyno to 677 hp-on pump gas. Making that kind of power in naturally aspirated trim and still include a warranty would be troublesome for some companies. For Edelbrock, it was easy, and they turned to a longtime partner, and multiple Pro Street and Pro Modified champion, Pat Musi, to help design this outrageously powerful crate engine. Pat Musi Performance builds... Pat Musi Performance builds a 555ci crate engine sold under the Edelbrock brand. These two powerhouses teamed up several years ago when Musi made the switch to Edelbrock Nitrous. Since that time, the two companies have collaborated on EFI systems, new nitrous components, cylinder heads, and now crate engines. The two collaborated to bring forth a powerful-yet street-worthy-combination, and launched it in 2007. Edelbrock had released version 1.0 of the bullet, which made 675 hp (EFI version) and 650 hp (carburetor on top). The first public glance at the engine came during a popular weeklong cruise where Vic Edelbrock's '67 Chevelle-equipped with the Edelbrock/Musi 555-completed the entire tour without a hiccup. It proved the engine's ability to withstand the rigors of street cruising and still retain a healthy power curve. The EFI version in Vic's Chevelle knocked down 19 mpg during last year's cruise. The car was equipped with a Tremec TKO six-speed and 3.31 rear gears. The carburetor induction saw 4 mpg less, as Edelbrock observed 15 mpg in the same Chevelle during previous tours. Since that time, the folks at Pat Musi Performance and Edelbrock continue to think of better ways to offer this popular 555ci powerplant. This year, the team decided to change the cylinder heads from the Victor 24-degree rectangular port, to the Performer RPM XT (Xtreme) heads. "The exhaust port is in the stock location with the XT heads. That means our customers won't have to rely on a custom set of headers when installing the 555," commented Smitty Smith of Edelbrock. Not only did the XT heads allow for off-the-shelf headers, but the heads also bumped the horsepower up. The CNC-ported heads swelled the big-block's rating from 675 hp to an even better 697 hp-on pump gas-with the EFI system. Musi selected a Scat 4.250-inch... Musi selected a Scat 4.250-inch stroke crankshaft, made of cast steel, for this engine. The steel material makes it a tough unit capable of withstanding abuse-especially from nitrous. It is one of the reasons Edelbrock offers a two-year warranty with unlimited mileage. We're already familiar with the Scat 9000 cast-steel crank, as we've been abusing this very same crank in our '68 Chevelle's 496 big-block. Edelbrock used EFI induction for the big rating, but we saw impressive results from a carb setup on an engine at Pat Musi Performance during our photo shoot. They officially call the carbureted combo a 676hp package, and we saw one bullet produce 677 hp. It shows how dead-on the advertising numbers are in the company's literature. While we didn't do a back-to-back test with the different induction components, Edelbrock and Musi told us that the EFI was worth 20 to 25 hp more. Musi was quick to explain the power difference between the two induction systems on this engine: "The main reason the EFI makes more horsepower is that the throttle body flows more than the [800-cfm Thunder Series AVS] Edelbrock carb." He explained how the throttle body is similar in size, but doesn't have the restrictive venturis to block the air coming in. Musi equated it to adding a Dominator to the engine, which would make a lot of more power than the Thunder Series carb, but driveability would suffer. The EFI is void of that problem, thanks to it being able to control the fuel and spark delivery. Pat Musi Performance builds all the engines, and each carries a two-year warranty with unlimited mileage during that time. The engine is based on a Dart M block with a standard 9.8-inch deck height, making it fit very well under the hood of most muscle cars. Musi then bores each cylinder hole to 4.560 inches. Mahle forged pistons have been chosen, and the flat tops contribute to the 10:1 compression ratio. Musi sourced Scat for a set of steel connecting rods and a steel crankshaft (4.250-inch stroke). A Moroso oil pump and pan keep everything lubricated. Scat H-beam steel rods complement... Scat H-beam steel rods complement the Scat stroker crankshaft. The rods check into this affair with a length of 6.385 inches. A coated set of Mahle pistons was also tapped for this bullet. We don't doubt the toughness of the short-block; Musi told us of several 555s in service that inhale nitrous on a regular basis. Musi tested an earlier version of this engine with an Edelbrock Performer RPM nitrous plate (110 jet) and blasted the 555 to 1,018 hp and a max torque output of 1,140 lb-ft. He was happy to report that the customer still runs the engine after two years of abuse. Musi was also working on a prototype Edelbrock throttle body during our visit. He started with Edelbrock's four-barrel-style universal throttle body and is adding a nitrous port in the center. The nozzle will spray down into the manifold and will be run as a dry-shot of nitrous. That means only nitrous will be sprayed through the system, and the EFI will add the additional fuel required. It will offer a clean look while packing a massive punch-up to 400 hp Musi says. A closer look at the Mahle... A closer look at the Mahle pistons shows each slug has a dual coating. The initial coating is on the piston for protection, while the secondary coating is on the piston skirt. The coating on the skirt reduces wear and friction. Earlier Edelbrock big-block crate engines didn't have this upgrade. "We went with a triple nickel because the bigger bore helps the head breathe better. That bore also allows a guy to go with a bigger one if he wears out the engine. The 555 is a really nice combo," Musi says. There is nothing like a joint venture to bring two powerhouses together to deliver a powerful and reliable product.
| BY THE NUMBERS |
| EDELBROCK/PAT MUSI PERFORMANCE |
| 555CI RPM XT CRATE ENGINE |
| Engine type: |
big-block Chevy |
| Displacement: |
555 ci |
| Bore: |
4.560 inches |
| Stroke: |
4.250 inches |
| Block: |
Dart Big M 9.8-inch deck iron |
| Crankshaft: |
Scat 4340 steel |
| Connecting rods: |
Scat 4340 steel |
| Pistons: |
Mahle forged |
| Camshaft type: |
Edelbrock Rolling Thunder |
|
Performer RPM hydraulic roller |
| Valve lift: |
.632-inch intake, .648-inch exhaust |
| Camshaft duration: |
248 intake/256 exhaust, |
|
at .050-inch lift |
| Cylinder heads: |
Edelbrock Performer RPM XT |
|
(PN 51559), CNC-ported |
| Intake valve diameter: |
2.300 inches |
| Exhaust valve diameter: |
1.880 inches |
| Compression ratio: |
10:1 |
| Rocker arm ratio: |
1.7:1 |
| Intake manifold: |
Edelbrock Victor Jr. |
|
454-R (PN 2902) |
| Recommended fuel: |
pump gas |
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with minimum of 91 octane |
| Max horsepower: |
677 at 5,800 rpm |
| Max torque: |
649 lb-ft at 4,800 rpm |
| Total cost, as-tested: |
$12,800 (carb) |
|
$16,500 (EFI) |
| ON THE DYNO |
| RPM |
TQ |
HP |
| 4,000 |
603 |
470 |
| 4,100 |
609 |
489 |
| 4,200 |
615 |
501 |
| 4,300 |
620 |
518 |
| 4,400 |
626 |
533 |
| 4,500 |
631 |
550 |
| 4,600 |
636 |
562 |
| 4,700 |
641 |
578 |
| 4,800 |
647 |
597 |
| 4,900 |
649 |
615 |
| 5,000 |
653 |
629 |
| 5,100 |
655 |
643 |
| 5,200 |
657 |
655 |
| 5,300 |
653 |
664 |
| 5,400 |
648 |
668 |
| 5,500 |
642 |
674 |
| 5,600 |
633 |
675 |
| 5,700 |
622 |
675 |
| 5,800 |
613 |
677 |
 A Dart Big M engine block,...  A Dart Big M engine block, with a traditional 9.8-inch deck height, is filled with the Scat crank, Scat rods, and Mahle pistons. Matt Ciarfello of Pat Musi Performance installs the piston using a tapered ring. It compresses the rings so the slug can slide right in. A rubber mallet is used to tap the piston into the bore.  Once the piston is in place,...  Once the piston is in place, the rod cap is bolted on from the underside of the engine. A good engine stand will allow the engine to be rotated upside down. Ciarfello torques the ARP rod bolts to 65 lb-ft with moly lube.  An Edelbrock hydraulic roller...  An Edelbrock hydraulic roller camshaft (PN 2264) was selected for the engine. While the .632/.648 valve lift, 248/256 duration, and a lobe separation of 112 degrees might sound large to small-block fans, it really isn't too big for a healthy big-block combination like this one. It offers a healthy idle and a powerband that goes up to 6,000 rpm.  One of the main advantages...  One of the main advantages of a hydraulic roller camshaft is the roller tip on the lifters. Roller lifters improve valvetrain durability and reduce friction, which will increase horsepower. It also allows for a more aggressive cam profile, since flat-tappet lifters cannot handle the quicker opening and closing rates of the hydraulic roller camshaft lobes.  Musi selected a Moroso oil...  Musi selected a Moroso oil pan, like he prescribes for all the engines coming from his famed engine shop in Carteret, New Jersey. An oil pan does more than just hold oil; Moroso incorporates baffles inside the pan to ensure the oil remains in reach of the oil pump during hard acceleration and movement.  A Fel-Pro head gasket is used...  A Fel-Pro head gasket is used to seal the head and block together. Another piece of the puzzle is the use of ARP head bolts to fasten down the head and hold it in place. Ciarfello torques the heads down to 70 lb-ft.  The Edelbrock Performer RPM...  The Edelbrock Performer RPM XT cylinder heads (PN 51559) come CNC ported. The intake runner volume is 344 cc, and flows 377 cfm at .700-inch lift. Moving to the exhaust side, the port volume is 142 cc, and it flows 271 cfm of air at .700-inch lift.  The combustion chamber has...  The combustion chamber has also been run through the CNC mill, and displaces a volume of 118 cc. The intake ports admit the air and fuel mixture though 2.300-inch intake valves. The exhaust escapes the cylinder through 1.880-inch valves. The best part of the head is that off-the-shelf headers will bolt on easily, unlike the previous version of this crate engine that required custom headers.  Musi turned to Gold Crane...  Musi turned to Gold Crane 1.7:1 roller rocker arms, and right now there is ample stock of these rocker arms on the shelf at both companies.  An Edelbrock Victor Jr. 454-R...  An Edelbrock Victor Jr. 454-R intake manifold was bolted to the top of the engine. It is a single-plane intake with a 4150 flange and an operating range of 3,000 rpm to 7,500 rpm. The intake is available in both carbureted and EFI versions, and has provisions for a direct-port nitrous nozzle system.  Like all Edelbrock products-the...  Like all Edelbrock products-the parts are proudly made in the U.S.A.  While Ciarfello handled the...  While Ciarfello handled the engine assembly, Musi was called in for the dyno session. The 555 cracked off 677 hp and 657 lb-ft of torque. Musi said that a switch to EFI would add another 20 to 25 hp due to the better flowing throttle body.  We tested the carbureted version...  We tested the carbureted version of the Edelbrock/Musi 555 ci. Here, Ciarfello bolts on the 800-cfm Thunder Series AVS carburetor. This carburetor is available in a few exterior finishes, but it is the Qwik-Tune Secondary Air Valve that we like most with this carburetor. This valve is easy to adjust while on the vehicle, and allows virtually limitless calibration of the secondary circuit with simple handtools.  Here is a new kit that Edelbrock...  Here is a new kit that Edelbrock is going to offer with this engine, and as a stand-alone system. It is the Pro-Flo XT fuel-injection system, by EFI Systems, and it is a follow-up to the Pro-Flo system. The XT system is designed for street cars with high impedance fuel injectors. Think of it as a basic version of the Pro-Flo EFI that Musi employs on his Pro Street and Pro Mod racing engines.
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