Edelbrock/Musi 555ci Engine Build, Part II

In part one of this three article series, we looked at our bad ass Edelbrock/Musi five-fifty-five big block crate engine destined for our project car that we lovingly call “Grandma”. Project Grandma is a late 70’s Chevy Malibu, appliance white, with bench seats. Something that your dear old Grandma would drive to the church on bingo night. Well, we’re planning on taking Old Granny and slamming 1,000+ hp through her. Nice, huh.

Our friends at Edelbrock suggested that we sneak in a little muscle under the hood. Well — a lot of muscle under the hood, to be honest. Vic Edelbrock explained to us that a collaboration with Pat Musi Performance resulted in the Edelbrock/Musi Five-Fifty-Five crate engine which makes major power, is tame enough to drive in traffic and can still manage to get an economical 20 miles per gallon of gas.

“What the consumer is buying in this 555 crate engine is Edelbrock’s quality parts, and our thirty plus years of experience bringing out the best in the Chevy big block engines,” explain Pat Musi, owner of Musi Performance. “We were building big blocks as far back as 1967 – long before it was cool. Back then we were building 512 cubic inch big blocks, now we’re building a 555 big block with modern technology.”

We jumped at the chance to have one of the first production run Edelbrock/Musi 555 crate engines, and the added bonus of having the engine built at Pat Musi’s performance shop, by the man himself, was simply too big of a deal to pass up.

We already did the first part of the Edelbrock 555 build. In Part 1, we covered the Dart Big-M Block, Scat Crankshaft and Connecting Rods, JE/SRP Pistons, the Edelbrock Hydraulic Roller Camshaft and the Moroso Oil Pan. In this article, part two of three, we are going to be discussing the rest of the engine components to the level that is commonly referred to as the long block. That’s pretty much the long and short of it (block wise, that it)!

Let’s take a look at each of the key areas of the build, and follow along with the 555 as it is assembled at Musi’s.

Edelbrock Victor/Musi 24-degree Cylinder Heads

Choosing cylinder heads for Chevy performance engines can be like battling the ancient beast Hydra. In Greek mythology, the Hydra had a serpent body with many heads. The number of heads varied based on the story but ranged from 5 to 900. Picking a head to do battle with was the demise of many would be warriors. There are more Big Block Chevy heads on the market than even a Hydra killer could deal with. We chose the Edelbrock Victor/Musi 24-degree heads for our 555.

The Edelbrock/Musi heads are conventional-style Big Block Chevy heads which are rolled over 2-degrees on the valve angle. These are part #61409. They feature 2.30/1.90-inch valves, Manley springs, titanium retainers and locks, and flow over 417 cfm at .900-lift.

Below are the full specs:

• 2.30-inch intake valves
• 1.90-inch exhaust valves
• Made from A356 T-6 aluminum
• Manley springs, titanium retainers and locks
• 114cc combustion chambers
• 377cc intake ports that flow 417-CFM at .900-inch lift
• Conventional port location
• Ready-to-use right out of the box
• Capable of generating 950-plus horsepower
• Designed by 8-time Pro Street World Champion Pat Musi

With so many to choose from, making the right choice can make or break a high performance warrior. We asked Pat Musi, a master of airflow dynamics for performance engines, how he developed the Edelbrock Victor 24 degree heads to take into battle on the tracks.

Musi explained that the Edelbrock Victor 24 degree CNC heads destined for the 555 crate engine are built with “a five degree cant instead of a four and a half degree cant which places the valve pocket closer to the piston center”. According to Musi, many of the standard heads direct the intake air closer to the ring lands, which can be catastrophic in a nitrous fed engine. Moving the valve pocket closer to the piston center has a distinct power advantage as well.

Valvetrain & Induction

Once the heads were securely bolted on by Team Musi, it was time to worry about making sure the valves opened and closed. Musi and Edelbrock spec out their 555ci crate Engine with Crane Gold Rockers arms.

Crane Cams does claim their Gold Race Extruded Roller Rocker Arms are racing’s most popular aluminum rockers since they hit the market in 1964. Claiming over four million of these units sold, we are reminded of the Elvis Presley album “50 Million Elvis fans can’t be wrong”. If the world had more big blocks, we’d have more Gold Race Roller Rockers. As it is; four million Gold Race Roller fans can’t be wrong.

Crane Gold Rocker arms feature needle-bearing fulcrum, a roller tip and are extruded aluminum for strength and reliability. The standard big block Chevy ratio of 1.7:1 is utilized in this engine, and with proven quality of these rocker arms, we can be assured of the ratio accuracy. These rocker arms are distinguished by the classy gold anodized covering and look bitchin’ on the top of Edelbrock’s 24 degree Victor heads.

The Intake – Edelbrock Victor 454-R

To help Grandma breathe better, our crate engine is equipped with Edelbrock’s newest intake manifold in the Super Victor line – the Edelbrock Victor 454-R Aluminum Intake Manifold. Designed specifically to match the Edelbrock/Musi heads, with a 3/4” radius and extra large oval port openings, the performance ability of this intake exceeds the demands of our 8 air hungry pistons. The perfect match for our high airflow requirements.

Edelbrock’s Pro Flow 2 Fuel Injection System

The Edelbrock/Musi 555 is available in two configurations: Carb or EFI. For us, it was a no brainer. The EFI version made more horsepower with greater durability courtesy of the Edelbrock Pro Flow EFI system.

Edelbrock has hit the ball out of the park with another out of the box kit that offers high performance in a comprehensive, easy to install package. The Pro-Flo 2 adds sequential electronic fuel injection to our Big Block with the additional benefit of programmability. With the addition of this system our Grandma will be a cutting edge fly girl with a powerful electronics package that she never could have dreamed of. The beauty of the Pro Flo XT EFI system is that the tune in the Musi 555 is designed for use with 91 octane pump gas and has an idle that is completely livable in a daily driver.

Pro-Flo XT’s Programmable ECU’s is the brains of the Engine Management System. As such, controlling the Engine Management System is the Pro-Flo XT Electronic Fuel Injection ECU. It’s a very sturdy unit, self contained, but it is recommended that mounting the unit away from the typical enemies of electronic components like heat and vibration. Under the dash or behind the glovebox are typical locations for mounting. The Pro-Flo system uses the speed-density method of electronic engine management in which fuel and spark requirements are based on engine speed and engine load.

Engine speed is determined by inputs from the distributor and the load factor is determined by inputs from the coolant temperture, the MAP & MAT sensors. Once the ECU has determined the engine operating point, calibrated tables programmed into the unit instantaneously control the the correct spark advance and injector pulse width. The unit is completely adjustable in the calibration mode and will allow modifications of the spark and fuel tables at various engine speeds.

Handheld Calibration Module

One of the neatest gadgets in this kit is the hand held calibration module that allows for tuning without the need for a laptop. The Pro-Flo system comes with a software package that allows for endless tuning calibrations that anyone can perform. Installation of the Pro-Flo package is simplified by the quick disconnect wiring harness.

Edelbrock Pro-Flow EFI Parts List:

  • Fuel rails (part # 3633)
  • ECU power relay (part #3586)
  • MAP Sensor (part #36019)
  • MAT Sensor (part #3588)
  • Coolant temperature sensor (part #36012)
  • Throttle body (part #39783)
  • IAC Motor (part #36017)
  • TPS Sensor (36018)
  • O2 Sensor (36013)
  • High pressure fuel pump (part #1790)
  • Fuel pressure regulator (part #1729)
  • Fuel Injector (part #3687)
  • Mallory Distributor (part #54-3564)
  • Calibration Module (part #37-9804)


How does it work?

The Pro Flo system interpets engine operating conditions and requirements by means of five sensors that are also included in the kit:

The Manifold Absolute Pressure (MAP) sensor is mounted on the air valve and converts air pressure in the intake manifold into an analog signal that is sent to the ECU.

The Manifold Air Temperature (MAT) sensor measures air temperature and is installed in the base of the air cleaner.

Coolant Temperature sensor is a device like the MAT sensor but measures the temperature of the coolant at the manifold on the driver’s side.

An integral part of the Pro-Flo throttle body, the Throttle Position sensor (TPS) measures the throttle angle.

Lastly, an O2 sensor measuring the oxygen content in the exhaust stream and relays that information to the ECU. The Pro-Flo system is capable of using either a narrow band or wide band O2 sensor. The included wide band sensor calibration is for use with the Dynojet wideband Commander Air/Fuel Ratio monitor.

Plus an extra advantage

Our crate engine comes with an additional, one of a kind component that makes it unique among the Edelbrock/Musi 555 crate engines. Grandma’s engine sports the Victor Series valve covers that all of these crate engines come with standard. Our’s however, has been signed by Pat Musi and Vic Edelbrock after a monumental dyno run at Musi Performace. But we will get to the dyno testing in our next segment.

The die-cast aluminum, black powder coated valve covers are annotated with the date of the event and the words: 1st 1,050 hp crate engine. When we lift the hood on Grandma, and these signatures see the light of day, Grandma will have no peers. These unique valve covers will strike fear in the hearts of all that line up against Grandma.

Finally, Fuel is supplied to the system by Edelbrock’s high pressure electric fuel pump (part number 1790). Self priming on key-up, the fuel pump will shut down if it does not receive an engine run signal from the ECU as a safety precaution. Also included in the Pro Flo system is Edelbrock’s fuel pressure regulator (part number 1729). The pressure regulator is factory preset at 50 psi and needs no adjustment normally. Excess supplied fuel that is not injected is returned back to the tank via a fuel return system built into the regulator.

Our long block is finished.

We still have one more video coming up on this build, and a final article in this three part series. Grandma will make it to the track once we get a roll cage in her that is adequate for this monster horsepower beast. Vic Edelbrock and Pat Musi both claim that the 555 crate engine is docile enough to drive on the street and get almost 20 mpg.

Uh, yeah. That may be true, but only if my old maid aunt is behind the wheel. Our plans are to take Grandma out and let her shred some rubber and tattoo her name on the asphalt.

Next time we’ll give you the full story about the dyno thrash we did, and the final power numbers.

Article Sources

About the author

Bobby Kimbrough

Bobby grew up in the heart of Illinois, becoming an avid dirt track race fan which has developed into a life long passion. Taking a break from the Midwest dirt tracks to fight evil doers in the world, he completed a full 21 year career in the Marine Corps.
Read My Articles

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