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The LS Swap Alternative? How Holley's Sniper EFI Transformed Our 1970 Pontiac GTO

In the previous update on our 1970 Pontiac GTO project car, we covered some of the thought process that goes into deciding whether it's better to build or upgrade an original V8 or swap to a modern powerplant like the ubiquitous LS engine as so many have done. 

In the case of the GTO, despite its ancient bones, the big Pontiac 455 under the hood was just too cool to give up. Yes an LS swap could have easily brought us less weight, more power and much better fuel economy, but it's nice to see old Pontiacs that still have genuine Pontiac engines. 

1970 Pontiac GTO on Trans Am Race Engineering Wheels and Nitto NT555 G2 Tires

And thanks to Holley Performance, we found a solution that would help to modernize the old school 455 while retaining all of its original charm (and performance).

Rochester Quadrajet Carb on Pontiac 455 Engine

The solution came in the form of a Holley Sniper EFI kit—one specifically designed as a direct replacement the Rochester Quadrajet carb that our GTO, as well as countless other GM vehicles, used. Of course you can also get Sniper kits to fit a variety of other carb/manifold types. 

Holley Sniper EFI Master Kit

Sniper EFI 101

If you aren't familiar with Sniper EFI, it's one of the most impressive aftermarket upgrades out there. It's a true-bolt on upgrade, with a throttle body that includes a self-contained ECU, and for many cars (including the GTO), you won't even need to change the intake manifold. 

Holley Sniper EFI Throttle Body

We got in touch with Holley and spec'd out a master kit that included everything we'd need, including the throttle body in "classic gold" finish, upgraded fuel module and in-tank pump, all required fittings and line and a 3.5 inch LCD tablet for setup, tuning and monitoring of the EFI system.

Holley Sniper EFI Master Kit Install

Bye Bye Carb

With everything in hand, it was time to begin the install. First order of business was to pull off the old Rochester carb, thanking it for its many decades of service as it went onto the shelf. 

Rochester Quadrajet Carb

Fitting the new Sniper throttle body with its four 100lb/hr fuel injectors was about as simple as replacing the carb itself. And it's especially nice that the ECU is mounted inside the throttle body itself so there's no need for extra wires or an externally mounted computer somewhere. 

Holley Sniper EFI Kit on Pontiac 455

Another great thing about doing an install like this in the modern era is that in addition to the printed installation instructions included with the kit, Holley has numerous detailed videos on YouTube that go through the process step by step.

Pontiac 455 Holley Sniper EFI Install

Along with fitting the throttle body atop the intake manifold and hooking up all the required lines, the EFI system also requires fitting a clamp-in oxygen sensor to the exhaust beneath the car.

Holley Sniper EFI 02 Sensor Install

Fuel System Upgrades

The most challenging part of the entire install was dropping the fuel tank and cutting a hole to install the new high-pressure fuel pump the Sniper EFI needs.

Holley Fuel Pump Install Pontiac GTO

There was nothing abnormally difficult about installing the fuel pump, but removing the lines, dropping the tank, fitting the pump and then re-running the lines was about the most time-consuming and physically intensive part of the entire project.

Holley Sniper EFI Fuel Line Install

With everything fitted, one the last things to do was use the included 3.5" touchscreen to complete the setup. This is also simple, you select which kit you are running, the size and some other basics about your engine, your target idle RPM and the computer does the rest. 

Holley Sniper EFI LCD Screen

Another cool thing about the Sniper Quadrajet setup is that it works perfectly with the original Pontiac air cleaner, which is great for those who want to stick with an OE look under the hood. 

Pontiac GTO 455 Engine

Back on the Road

The aforementioned touchscreen computer helps you make sure all the sensors are reading right, and the small screen can easily be mounted inside the car for easy access and viewing. And with that it was time fire the car up.

Holley Sniper EFI Screen Pontiac GTO

Immediately noticeable was how much smoother and faster the GTO was to fire up. No more needing to pump the gas pedal just right or struggling with a cold engine that doesn't want to idle. 

Pontiac GTO on Nitto NT555 G2 Tires

The 455 still sounds the same, with a nice-sounding idle from its mild cam—Holley even designed the kit to retain the "signature Rochester roar" at wide-open throttle.

Holley Sniper Quadrajet EFI Pontiac GTO

As for performance, we haven't had the chance to race the car or to take it on a long road trip, but from the seat of our pants it feels very similar to the old carb setup.

1970 Pontiac GTO Hood

 There's still plenty of power to smoke the Nitto NT555 G2s when desired. And if we decide to add more power later on, the Quadrajet Sniper is good for fueling up to 500 horsepower. 

1970 Pontiac GTO Burnout

Our first impressions are that it's basically the same GTO as before , but with much better manners, easier starts, and a lot more consistency in both performance and drivability.

Holley Sniper EFI on Pontiac 455

Or to put it another way, a less temperamental car is a car that you want to drive more often, and that's better than anything. 

1970 Pontiac GTO Orbit Orange on Nitto NT555 G2

So if you have a vintage project vehicle and are debating about sticking with your old school carbureted V8 or pulling it all out and going with a modern swap, a Sniper EFI kit might just be the perfect middle ground between the classic muscle of yesterday and the high tech muscle of today. 

Holley Fuel Injection

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