Edelbrock’s 555 Gets Nitrous’d & Dyno’d

Ok, here’s the rub. This haul-ass crate engine is going into our Project Grandma build car. Grandma is a 1978 Chevy Malibu that came stock with 3.8 liters of V6 power producing an anemic 105 horses. It was a real “get you to the church on Sunday” car, but not fear-inspiring in anyone’s book. Putting the Edelbrock/Musi 555 crate engine topped with a shot of nitrous in our Malibu is one hell of a transformation for this formerly sedate ride. You can just call us the “Devil’s advocate” on this one.

In the first two parts of our Edelbrock/Musi 555 crate motor build we showed you what it took to put together a pretty simple, yet powerful crate engine program using the mind of Pat Musi and the manufacturing might of Edelbrock. With the theory and assembly now out of the way, it is time to put the engine on the dyno and see how it lives up to the expectations that were laid out on paper before the project began.

In Part One we got our hands on this big-block and we provided details on the components in the short-block build. We highlighted the Dart Big M block with a priority main oiling system, the stalwartly JE forged pistons, Scat’s single twist forged steel crank and the Scat high performance H beam rods.

In Part One, we showed you how the short block went together.

In Part Two we took a closer look at the long-block components of this monster crate motor, including the Edelbrock Pro-Flo XT electronic fuel-injection system. With the Pro-Flo’s new technology, our big-block is tame enough to be a daily-driver or bad enough to be a terror on the track. Vic Edelbrock assured us that we could get 20 mpg with this engine – if we drove the speed limit.

Part Two topped the block with Edelbrock heads and the Pro Flo XT fuel injection system.

In the final segment of the series we’re putting the Edelbrock/Musi 555 crate motor on the engine dyno and spray it down with nitrous to see if the power we expected is actually there. Naturally, with guys like Pat Musi and Vic Edelbrock behind the project there was no reason to doubt the engine wouldn’t produce as advertised, but in the world of making big power, if it can’t be backed up on the dyno and on the track, it is of little value. Lets face it; racers race with power, not numbers on paper.

Our monster crate engine on nitrous, ready for the dyno.

The brains behind the brawn.

For those of you who have been living on Mars for the past fifty years, Edelbrock and Musi are both legends in the aftermarket performance world. Vic Edelbrock, Jr. led the way for hot rodders in the 60’s and 70’s while growing the company his father founded into one of the best-known names in street performance and racing.

Vic Edelbrock, Jr. still guides the company his father founded and he brought to prominence.

Pat Musi is pure magic. An 8-time World Champion drag racer and engine builder/designer that started racing as an 18 year old street racer on the eastern expressways, Musi has become a master at massaging engines and cylinder heads to get “just a little more” out of them. Musi-built engines are sought after world-wide, and there aren’t too many guys who have more experience with big motors on spray than him.

Pat Musi, World Champion Racer and Engine Builder.

The Dynamic Test Systems (DTS) engine dynamometer at Musi performance is a specially modified by DTS for multi-stage nitrous systems. The DTS engine dyno has extremely good control characteristics, and is capable of controlling the engine speed within five rpm at steady state testing. The dyno is also capable of running in either direction. Most domestic engines run in a clockwise direction where some foreign and marine engines run counter-clockwise. The DTS engine dynamometer is well suited for high horsepower testing by utilizing two control valves at the same time for quick response to engine demands. This is extremely important when making dyno runs on nitrous engines.

Our crate engine on Musi’s DTS engine dynamometer.

Truth in Testing.

Every time an engine is being hooked up the dyno, the first question is, “So, how much do you think she’ll pull?” Part of the enjoyment of running an engine on the dynamometer is seeing what the expectations are, and then what the truth is. Sometimes feelings can get hurt when expectations exceed reality. For the baseline run on our engine, there were no secrets. Edelbrock and Musi had been working on this crate engine package for three years doing all the research and development that makes a high-performance package a durable trouble-free product. These years of development and testing gave everyone a pretty good idea of how much power the engine would make straight out of the crate. The research and testing phase, although necessary, stymied Musi’s eagerness to get the engine to the track. “That Edelbrock crew doesn’t cut any corners. I’m just a racer and I wanted to get this engine put together and go racing, but those folks put this engine through years of testing,” Musi explained.

Advertised Horsepower & Torque numbers.

Baseline Run on Pump Gas.

The published power numbers are great for a pump gas crate engine and everyone at the dyno facility wanted to see verification. The published power numbers show 675 horsepower at 6,000 RPM and a peak torque rating of 650 ft/lbs at 4,500 RPM.

Our initial pull was actually a few horses above the published power numbers.

Our first run at the Pat Musi Performance shop verified the published numbers showing 677 HP at 5,800 RPM and peak torque of 662 ft/lbs at 5,100. A very impressive run for our engine right out of the box, assembled on the stand with no massaging or modifications of any kind.

Pat Musi at the controls of the dyno for our baseline run.

Following the baseline run, Musi wanted to put his own tune-up on the engine. Musi, however, wasn’t allowed to add or remove any parts from the engine, just an experienced hand tweaking the flow and timing a bit. Those of us watching the run were making bets as to how much more could be gained simply by changing the fuel curve and timing. The average guess was around a five horsepower gain. Musi was claiming that he could add 13 HP easily.

Musi took some time to work his magic on the motor in NA form before the next pull.

After putting the “Musi magic” into the tune up, the crate engine was run again to check exactly how much voodoo “Popeye” had. End result: Seventeen additional horses gained with really only minor tweaks – 694 HP at 5,800 RPM. Musi claimed that he could get over 700 HP by manipulating the fuel curve a little more.

Time to get serious and add the bottle to the mix.

The next step was to install the Edelbrock Performer RPM Nitrous system and spray it. The plate was loaded with enough nitrous to equal about a 275 hp shot, and Musi adjusted the Pro Flow XT software to pull back some timing from the 666. Armed with the baseline dyno pull numbers, our guys were estimating a cool 950 HP on the nitrous pull. Musi was claiming that he was going to get 975 off of the first try on the bottle. Trusting Musi’s experience, Edelbrock was backing Musi’s claim. Our guys were more conservative.

Even with Musi at the helm, you still hold your breath for the first nitrous pull on a new motor.

What happened next surprised everyone, including the “Magic Man”. The nitrous dyno run with our crate engine, on pump gas and with a single stage of nitrous produced a peak horsepower of 1,050 at 5,000 RPM. Equally impressive was a peak torque reading of 1,140 ft/lbs at 4,600 RPM.

Why are these men smiling? They just built the first Edelbrock Crate engine to reach 1,050 horsepower on pump gas and a single shot of nitrous.

After the dyno run was made, and the data was retrieved, a round of congratulations and cheer made it’s way around the shop. Realizing the importance of the occasion, Musi and Edelbrock autographed the valve covers of the 555, and that’s the way it will go, straight into Grandma’s engine bay.

Taking advantage of the situation, we wanted to pick Musi’s brains on running engines on the dyno with Nitrous. After all, we don’t get the chance to study under a master very often, and learning things by trial and error can lead to destroyed engines and a mess to clean up. Being lazy guys (or smart guys depending on your perspective), we wanted to avoid cleaning the mess if we could. Pat was helpful enough to provide some tips based on his years of experience.

Pat Musi’s Top 5 Nitrous Dyno Tips

1. Find the right specialist.

See if the dyno is suited for nitrous. The valving is critical for the surge in power. If the dyno operator specializes in four cylinder import motors, taking a big block Chevy there might not be the smartest idea. There are major differences in running high horse power engines and endurance race engines on a dyno. Make sure that the dyno can log the data that you are looking for.

2. Experience Counts.

Start at a small horsepower level to get a feel for the power increase. There is no substitute for personal experience, so find a dyno operator that knows what to expect with a nitrous-injected motor.

3. Don’t run the engine pig rich.

Avoid running the engine too fat. The extra fuel will damage rings and ring lands. A little rich is ok, and even preferable. Too rich or a mixture on the lean side will destroy an engine or degrade the long-term performance.

4. One system at a time. Run multi-stage systems one at a time to get a feel for your tuneup. Give yourself plenty of time and don’t rush. Plan for running one system at a time in your schedule.

5. Stay in your comfort zone.

Running more than one stage is not recommended unless you have serious nitrous time on a dyno. Dodging flying engine components and cleaning up the dyno room is no fun.

Click here for the Edelbrock/Musi 555 Part 3 Photo Gallery

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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