Project Snake Eyes Takes MSD’s Atomic EFI 2 For A Spin

For those of you who have been following the Snake Eyes project series, you’ll remember our recent addition of a TorqStorm supercharger. We should note that we were back and forth on whether or not to provide our 383ci with fuel via a blow-through carburetor or a modern EFI system.

Scuttlebutt around the office had most of our fellow editorial types voting for EFI given the ease of tuning and modern performance implications. However, we landed on the decision to supply fuel with a QFT blow-through carburetor. The carb did its job well, and you can read about that installation, here. But when we spoke to the experts at MSD earlier this year, they had something new we just had to try – the new MSD Atomic 2 EFI.

Atomic 2 EFI

Unboxing the Atomic EFI 2 proves there aren’t many parts to the system. Installation is easy!

The previous generation of Atomic EFI was not capable of accomodating boosted applications, but we had great success with it on naturally aspirated engines. So when we spoke with Evan Perkins of MSD/Holley, and he reported the addition of boost capabilities, we had to try it out for ourselves.

New Features And Performance Improvements

The new features for the Atomic 2 EFI are numerous. Take the newly re-designed throttle body and booster mechanism for example. Evan broke it down for us like this, “The idea behind the booster design is to better distribute fuel by increasing fuel atomization. While any throttle body injection (TBI) system is somewhat subject to the intake manifold it’s sitting on top of, equal cylinder-to-cylinder air/fuel distribution is always the goal. The new design is a major step in that direction.”

But that was just the tip of the iceberg. It was as soon as Evan mentioned the unit is capable of blow-through and draw-through forced induction, our ears perked up and we had to know more. We inquired as to what changes were made from the previous version of the system that enables it to now handle the reported 21.5 psi of boost pressure.

The previous generation of Atomic was not designed for boost at all, so this is a major leap for the product line. – Evan Perkins, MSD/Holley

Evan tells us, “The previous generation of Atomic was not designed for boost at all, so this is a major leap for the product line. In the Atomic 2, we’ve included a 2.5-bar map sensor which is what allows it to read up to 21.5 psi of boost. The addition of laptop-tunability means the units are robust and adjustable enough to run well with boost.”

Atomic 2 EFI

The new booster design aids in fuel distribution and increases the overall performance of the Atomic 2.

That brought up an excellent point as laptop tuning is possibly the most notable feature that sets the Atomic 2 EFI apart from the previous generation. Evan assured us that the unit’s self-learning capability is retained. Despite this, he still pointed out, “Self-learning is an awesome feature, but when you start creeping up into the bigger boost and power numbers, it is always recommended to have a competent calibrator tune the engine.”

This was of particular concern to us, as we would be going for max-effort with the low-boost blower and SBC combination. Fortunately for us, Snake Eyes would be in the skilled hands of the professionals at Westech.

But before we could do any dyno tuning, we had to install the Atomic 2 system, and that meant making some considerations.

System Considerations

We asked Evan what system requirements we needed to factor in when upgrading from the carburetor to the Atomic 2. He explains, “The biggest thing to look at when moving from a carburetor to EFI is the fuel system. The Atomic 2, like any EFI system, is going to require a significantly higher fuel pressure, which most carburetor-style fuel pumps aren’t designed to deliver. In addition to that, it’s always a good idea to make sure other systems, such as the ignition, are working properly and are compatible with EFI, meaning they generate as little RFI as possible.”

Fortunately, we’d already upgraded the entire fuel and ignition systems on Snake Eyes. The fuel pressure regulator we were previously using for the blow-through setup wouldn’t supply enough fuel pressure for the new Atomic 2 EFI. Because of this, we swapped that out for a vacuum-referenced Holley unit (part number: 12-882). Other than that, we were all set to bolt on and plug in.

Atomic 2 EFI

We swapped out our old fuel pressure regulator for Holley’s 12-882 that’s capable of handling fuel injected pressures.

As we unboxed the Atomic 2 EFI kit, we couldn’t help but notice its sleek and timeless looks. For such a technologically advanced unit, it maintains a familiar aesthetic. We asked Evan how they managed to incorporate the ECU into the throttle body and still maintain a great form overall.

Evan replied, “The short answer here is we have an extremely talented team of EFI engineers that not only worked wonders with the system packaging, but also with the tuning ergonomics, ease of installation, and overall performance.”


We’d already removed the carburetor from the intake manifold before we began the installation, so we had a blank slate. Installing the Atomic 2 EFI is like installing any 4150-style carburetor with the added step of routing some wiring. Truthfully though, it was as simple as it gets.

The 4150-style flange makes bolting the Atomic 2 on most intake manifolds as easy as any carburetor.

We set the unit atop the intake manifold and bolted it on using the studs we’d used before. Even the throttle cable, transmission kickdown, and return spring all hook up the same way.

We were already running all of our vacuum lines to a distribution block that was referenced directly from the intake manifold. However, if we needed to, we could use one of the three reference ports on the throttle body (two are manifold and one is ported vacuum for a distributor advance).

EFI upgrade

The Atomic 2 comes with -6 AN fittings for the throttle body’s fuel inlets. We made our own fuel line to the regulator, but there are plenty of fuel logs out there that do the same thing.

The fuel inlets on either side of the throttle body come with -6 AN fittings, so we needed to plumb new braided lines to our new regulator, which didn’t take up too much time.

Next, we moved on to the wiring. Don’t let that word scare you off though. If you can splice a few wires, use heat shrink, and zip ties, you’ll be fine if you attempt this install. The wiring harness that comes with the kit is very well thought out and provides ample lengths of wire where needed.

Atomic EFI 2

Connecting the throttle linkage of the Atomic 2 is the same as most Holley-style carburetors. The throttle cable, trans kickdown, and return spring are all in a familiar location.

The body of the Atomic 2 EFI houses the TPS, IAC, and fuel pressure sensors, so there aren’t many connections to make from the throttle body itself. In fact, the system only requires four wiring connections (battery +, battery -, 12v ignition, and rpm feed) to run, and there are only three other pre-terminated connectors (the handheld LCD screen, oxygen sensor, and coolant temp) to hook up.

Main Power

We took the unit’s main power harness which contains the four necessary wires for startup and hooked them up first. That included the red and black power wires that must be wired directly to the battery’s positive and negative terminals.

MSD stresses the importance of proper wiring techniques in its instructions. We used heat shrink connectors for the main power and ground wires.

Next, we connected the pink wire from the harness to the car’s ignition at a switched 12-volt source. It is important the pink wire is supplied with 12-volts, even while cranking which is why the ignition is good to tap into.

Speaking of ignition, our spark is controlled by an MSD ignition box. This means the yellow wire from the harness is unused. Instead, we wired the purple crank signal wire from the seven-pin connector to the tach output terminal on the ignition box.

Atomic EFI 2

There are five connectors coming from the throttle body that must be connected in order for the system to function – a 10-pin accessory connector, 7-pin main power connector, coolant temp sensor, LCD screen, and oxygen sensor.

Also connected to the main power harness is a built-in fuel pump relay. We previously had our fuel pump wired to receive constant power with a turn of the key. So we simply supplied the fuel pump’s positive terminal with power via the pre-installed relay instead. This enables the Atomic 2 EFI system to prime the pump when the key is in the acc position. Thus ensuring there is an adequate amount of fuel pressure for startup.


The ten-pin connector has provisions to wire accessories like digital gauges, electric fans, and A/C kick. But since ratty old Snake Eyes doesn’t have A/C and its fans were already wired independently, we didn’t need to utilize that feature. In fact, the only wire we ended up using from the ten-pin harness was the dark brown tach-output wire to our mechanical gauge.

Atomic 2 EFI

Wiring an EFI system to a car that never had it might sound like a. big task, but with only five connectors to sort through, it’s very manageable.


We routed the LCD screen connector through the firewall so we can monitor our engine’s vitals from inside the car.

We’ve often seen other systems use a large connector for their digital displays. The problem this creates may seem like a minor one, but the Atomic 2 EFI proves this is an inconvenience that’s easily avoided. The small connector allows users to pass the wire through factory holes in the firewall without modification. We don’t know about you, but we don’t exactly like drilling large holes where we don’t have to.

Atomic 2 EFI

The Atomic EFI 2’s LCD screen is where we cycle through the setup wizard and monitor the engine’s vitals. Luckily for us, MSD uses a small connector to hook into the throttle body. It makes passing it through the firewall very easy.

From the home screen, we can toggle through tuning, monitoring, pro features, logging files, and the setup wizard.

Coolant Temperature Sensor

The system comes with a coolant temperature sensor that provides the ECU with the engine’s operating temperature. We installed the sensor into one of our intake manifold’s unused ports and connected it to the throttle body.

The OEM-style coolant temperature sensor connects like most modern variants.

Oxygen Sensor

The Atomic 2 includes an OEM-grade Bosch oxygen sensor that allows the system to learn as you drive. The self-learning feature has been the calling card for the system as many users attest to the prowess of the previous generation. We asked Evan about the software and how it gained such a stout reputation in the community.

Evan adds, “Self-tuning software has come lightyears from where it began. Much of this is due to the improvement in oxygen sensors and their ability to provide near-instantaneous, wideband feedback that allows for the ECU to learn the engine’s requirements.”

The oxygen sensor included in the kit is what enables the self-learning and laptop tuning features of the system.

If you’re upgrading from a classic carbureted system, the Atomic 2 kit includes a no-weld flange to make tapping into the exhaust easy. Luckily for us, our headers already had an oxygen sensor bung welded in so we just used the supplied sensor and connected it to the corresponding plug from the throttle body.

The final step for our installation was putting everything back together. That included bolting on the supercharger hat.

Initial Startup And First Drive

Now that we had everything bolted on and wired up, we got ready for the initial startup and test drive by making sure our fuel pressure was adequate (55 to 56 psi) and the handheld powered up.

The setup wizard asks a few simple questions about the engine's specifications before we can start her up.

We took the handheld through the setup wizard by providing it with our engine specifications (number of cylinders, cubes of displacement, and camshaft type), power adder type, ignition type (cd box), and the target idle speed. After that, we turned the key to the acc position and the ECU began syncing.

We then cycled the key off and let the calibration load. Once it was done, we cranked the ignition and the engine sprang to life. The digital display was then providing us with real-time data, such as engine RPM, throttle position, MAP, CTS, IAC position, and battery voltage.

After loading the calibration, we turned the engine over and it sprang to life. The last photo shows the vitals while the engine is running.

With the car running, we felt confident about taking it for a spin around the block to test out the self-learning. But, as Evan mentioned, we were shooting for high-output numbers from our combination, so we really just wanted to test everything out and ensure all systems were operational before trailering it to Westech for some serious dyno tuning. For those looking to use the self-learning aspect, MSD’s instructions detail a thorough walkthrough.

Dyno Tuning And Results

After a short amount of time spent in the shop installing the Atomic 2 EFI, it was finally time to hook up the laptop, put the spurs to ol’ Snake Eyes, and make some all-out dyno pulls.

The supported horsepower ratings for the Atomic 2 system are listed as 650 hp for naturally aspirated applications and 635 hp for forced induction applications.

Atomic 2 EFI

Strapped onto the dyno, Snake Eyes made a previously not so impressive dyno run.

We asked Evan why the supported horsepower ratings differ from naturally aspirated to forced induction applications. He replied, “In a naturally aspirated engine at peak load, there is zero pressure to a slight vacuum in the intake manifold. In a forced induction engine, there is positive pressure in the intake. That positive pressure works against the fuel injectors, slightly reducing their ability to flow fuel. That is why you will often see an EFI system rated for different power in naturally aspirated and forced induction applications.”

Snake Eyes’ previous dyno run was less than stellar given the 383ci displacement, but overall, not horrible.

It was our tuner, Ish’s opinion that we’d likely find the limit of the Atomic 2’s four 100 lb/hr injector output before we reached the maximum horsepower capabilities of our engine and blower combination. That sounded promising to us, so we strapped in and let er’ rip.

After Ish worked his magic on the laptop, he was able to fine tune our unique engine/EFI/blower combination to the tune of 389.9 peak horsepower at around 5,800 rpm and 375.5 peak torque at around 4,800 rpm. That’s one heck of an increase for a blower and EFI combination that’s only turning out between 6 to 8psi of boost.

After the experts at Westech got ahold of Snake Eyes and the new Atomic EFI 2, we saw an increase of more than 100 wheel horsepower!

The ability to fine tune with a laptop enabled us to eke out the most from our combination. We did so with far more accuracy than anyone could with a carburetor and no monitoring system. In total, we saw an increase of more than 100 wheel horsepower from when the engine was naturally aspirated.

For more information on the Atomic 2 EFI system and everything else from MSD, head to the company’s website, here.

Article Sources

About the author

Vinny Costa

Fast cars, motorcycles, and loud music are what get Vinny’s blood pumping. Catch him behind the wheel of his ’68 Firebird. Chances are, Black Sabbath will be playing in the background.
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