Sniper EFI Update: Weeks Later, Do I Still Feel It Was Worth It?

Follow up. It’s not something that a lot of automotive writers are adept at doing. Normally, I’m one of those not-so-adept follow-uppers. Usually, deadlines don’t afford me the opportunity to go back and revisit an install I had done months prior. But this time, I made an exception. Before I installed the Holley Sniper EFI on my C10, I was skeptical about the benefits I heard I would get. Could it really work that well? A few months have passed, and I am certain you would like to know if it is actually delivering any substantial benefits.

As a refresher, the Sniper EFI kit I installed is rated for engines developing up to 650 horsepower. EFI is not something I was overly comfortable installing. Let’s face it, I had no previous experience before this. As I stated in the original article, I really have no background in EFI tuning – and even less knowledge of computer programming, so, upgrading to EFI had to be idiot proof.

EFI

I used the Holley Sniper Master kit PN 550-511k.

One of the great features of Holley’s Sniper is the ability to set your air/fuel ratio (AFR) where you want it. When I finished the install on my C10, I set it as follows: 13.1 at idle, 14.2 at cruise, and 12.9 at WOT. I also noted that after some time, I could change those values as I saw fit.

The install was completed on January 20, 2018, and it is now April 3, 2018. That’s 10 weeks that I’ve been driving the Cheyenne since the install. I’m still more than happy with how the system is working, and as I stated I might do in the original article, I did some tweaking to see if I could increase fuel mileage. To say I’m happy with the results is an understatement.

EFI

My initial idle air/fuel setting was 13.1. After a few weeks of “tuning,” the truck is happy with a 13.9 setting. Remember, this is not a later model Vortech engine with better cylinder heads. This is the original 1979 350ci small-block. Not the picture of efficiency when new.

When the truck was getting fed through the Quadrajet, my highway mileage was 10.5 to 11.0 miles per gallon. After installing the Sniper and running for a few weeks with the initial air/fuel settings as mentioned, I saw roughly 1 ½ to two-miles per gallon increase. Not only did the truck drink less fuel, it gained some drivability. But has it gotten any better.

In the original article, I mentioned I was not an EFI expert, but after some simple research – and with the help of the Holley tech line – I was able to inflict some simple adjustments to make the Sniper even better for my application. I started by adjusting the fuel prime – which squirts a small amount of fuel into the intake to aid in start-up. I can’t say whether or not I made any major improvements in that area, but I didn’t hurt it either.

efi

The “at cruise” air/fuel setting I settled on is 16.5. I went as high as 16.9 and noticed the engine starting to surge. I backed it down to this setting. It’s running great.

Next came air/fuel ratio adjustments. This is one area that too much really is a bad thing. The initial settings I chose were a happy medium between rich and lean, and as I said, initial mileage and drivability improved. The weeks following the install saw me slowly increase the air/fuel ratio numbers to lean the system. One thing to keep in mind: go too far and engine damage can result. To avoid that scenario, I slowly increased the lean-ness of the incoming charge until the engine just started to react negatively, and then backed off.

efi

I didn’t change the WOT air/fuel ratio too much – yet. I started out at 13.1

For example, I increased the lean-ness of the idle until I noticed the engine didn’t want to run very well after the initial start-up, and coolant temperatures started climbing irregularly. During normal cruise-mode on the Interstate, I slowly leaned the air/fuel ratio (increased numbers) until I noticed the engine starting to surge slightly. I then pulled over and enriched the fuel mixture (lower numbers).

I have adjusted the basic mixtures that I am comfortable with adjusting, and I am going to say that I was successful: the truck still runs, and I didn’t burn up any pistons. I think I’m done “tuning” the Sniper system, and the truck still runs as good as ever. As far as a fuel mileage increase? How does 14.0 to 14.5 on the highway sound? Yes, it varies a small amount, but my pressure on the load pedal and the amount of fuel I put into the tank at each fill up can vary a small amount as well.

I know that might not be as impressive as a late-model vehicle that gets 18-plus mpg on the highway, but that would be comparing apples and oranges. As far as I am concerned, the Holley Sniper system will be a permanent fixture on the small-block in my truck.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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