"I have a Holley on my…" "I just ordered a Holley for my…" "It needs a bigger Holley…" …or some variation on the theme. There's a good reason for that. The big "H" has been the carb of choice for everything from record setting Pro Stock drag cars, to truck pullers, to NASCAR champions, to off-road race trucks. The reasons are many. Tunability, parts availability, a wealth of knowledge written on how to build'em, hop'em up, and of course the fact that they work exceptionally well in a variety of applications….If you know what you're doing. Unfortunately the average gearhead isn't a carb whiz. Much like the mysteries of automatic transmissions, carb tuning is another of the so-called "black arts" of the motorsports / auto enthusiast world. Jet it lean and you can turn a perfectly good engine into scrap metal. Jet it rich and you'll suck gas faster than you can pump it …Well, it'll seem that way. With the new "Street Avenger" line, Holley has gone the extra mile to take most of the Voo Doo out of the carburetor, while leaving that legendary performance in. But is it really possible to make a true "bolt on" Holley? Will it perform as advertised, or will it be a sheep in wolf's clothing? Improving the Breed Based heavily on the traditional "4160" Vacuum Secondary performance carb, the Avenger comes in 4 sizes to suit a broad spectrum of engine displacements and performance levels. Available in 570cfm, 670cfm, 770cfm, and 870cfm models, you're fuelish needs are pretty much covered well into the 500 HP range. But what separates the Street Avenger from its older brethren?
4 Vacuum Ports, including PVC, Spark Advance, Power
Brake and Vacuum-Accessory.
"No Trouble" quick change adjustable Vac
Secondary
Gen 4 Power Valve with million mile blow-out
protection
Built in (replaceable) fuel filters
Electric Choke
All new fuel metering system, wet flowed at the
factory
Center hung, externally adjustable float bowls w/
clear "sight plugs" No doubt about it. There's a lot of good stuff to like While its named "Street Avenger", don't let that fool you. Features like center hung float bowls are the configuration of choice for the off-road crowd, where bouncing and high-angularity maneuvering are a way of life. The built in Power Valve protection is another feature welcome when the pavement ends. Gone is the fear of losing a power valve to a backfire in the event you bounced your truck around just a "little" too much through that last set of whoops. While Holley carbs have developed a reputation for blown Power Valves, the simple truth is that their engineers addressed, and solved the problem years ago.
Lastly, although you'll likely install an in-line fuel filter, the built in units will provide an added layer of protection in the conditions our vehicles endure. You might be surprised just how much nasty stuff can accumulate in your fuel tank over time - or worse yet, all at once (trust me on this one). All That Glitters Nickel plating is the first thing you'll notice when you open the box. There's no doubt that the carb will do wonders for your under-hood aesthetics, but that plating is there for more than looks alone. Holley plated the Avenger to add another level of protection to the carb, and off-roaders can use all the protection they can get. Fuel the Need With 400 mostly stock, but thirsty inches to feed, Holley recommend the 670cfm version of the Avenger. A full 70cfm larger than the carb it replaced, we expected to see an improvement in top end power, but ultimate power wasn't the goal - all around performance both on and off road was. That's actually a lot more demanding than it sounds. Race only carbs like the Holley "Double Pumper" series usually live their lives doing one thing - achieving power at the expense of all else. A street performance carb like the Avenger is asked to make great power, provide decent fuel economy, and contend with altitude changes and questionable fuel. Add to that, keeping the truck running smoothly in all types of off-road terrain. Is it going to spill over in the whoops? Is it going to flood out at high angles? Is it going to restart easily after a stall? A tall order? Most definitely. Installation: Installing the Street Avenger was a simple process on our 79 Ford's 400 CID engine. With our recent upgrade to an Edelbrock Performer intake manifold, it's a simple matter to install the supplied gaskets, drop the carb over the mounting studs, and torque it to spec. Using Holley's included fuel lines, it's an easy task to adapt the dual feed float bowls into the original fuel line coming from the pump. If you've opted for an aftermarket fuel pump, this would be a great time to install a fuel pressure regulator to ensure the Street Avenger isn't receiving more pressure than it needs. Different vehicles will employ different throttle cable mounting designs, and Holley includes some of the more common carb-side mounts right in the box. Our Ford uses a simple "ball and socket" arrangement, so there's nothing exotic to slow us down. Check all stock lines running to the carb for signs of wear , age, or cracking. Hose is cheap, and now is a good time to replace anything that even looks questionable. We've seen many baffling "carb problems" ultimately traced back to a 50 cent vacuum line. Make sure the air cleaner base doesn't interfere with proper operation of the choke or throttle linkage. As with any new product, take the time to ensure a proper fit of "all" related components. Be sure to cycle the linkage throughout its range to ensure sufficient clearance. Wiring the electronic choke will require you to find a "key on" hot wire. Holley's preset adjustment may or may not need changing depending on the temps in your area. It may take you a couple of warm-up cycles to get the setting that's best for you. The base calibration of the Holley Street Avenger is designed to give good performance and economy over a broad range of applications. As your skill and familiarity with the carb grows, you can begin dialing it in to achieve optimum performance for your conditions. The "Quick Adjust" Vac-Secondary diaphragm housing gives you easy access to your secondaries' control spring. Holley supplies both stiffer and lighter springs to help your tuning along. This is one of the easiest tuning modifications to make, and it can make a world of difference in your truck's performance. For those wanting to dial their carb in even further, Holley makes a "Spring Kit" which includes several springs not included with the Street Avenger. Rockin' in the Real World Before going on, we have to qualify the following: Flashback F-150 had suffered an engine fire that totally wiped out the under-hood area, and all engine accessories. The 670 Street Avenger served as a replacement carb for the Edelbrock Performer that was reduced to a blob of aluminum. Likewise, the Jacobs Off-Road ignition was burnt to a crisp (though the ceramic plug boots lived up to their "high temp" billing. In fact, that was about all that was left. In short, this wasn't to be a simple carb swap - off with the old, on with the new. It turned into somewhat of a nightmare, and when all was said and done, the Holley was totally blameless. After installing the 670 Street Avenger on our 400 CID engine and sorting out the mistakes of others, we were shocked to see that our highway mileage had jumped to 17 MPG - a full 3 mpg increase when combined with the new MSD Digital 6 Plus ignition! Now in all fairness, this wasn't an "out of the box" increase. We had jetted down the mains to a "61" primary / "65" secondary, and gone from a "6" to a "5" power valve while chasing down the ghost in the machine. Stock calibration was rich with the stock cam/cast iron exhausts at our altitude, but not so rich as to create significant problems. As the saying goes, no pun intended, your mileage (depending on altitude) may vary. Off-Road, the Holley proved superior to the Edelbrock in both high-speed/rough terrain, and under conditions of extreme angularity. While still no match for a properly calibrated fuel injection system, it's more than up to the task of providing excellent performance as an off-road carb. Add in the decades of proven tricks, tweaks and track time and you're not likely to be disappointed. Overall, the Street Avenger proved to be very forgiving of "tuner error", withstood multiple backfires without eating a power valve, provided crisp throttle response, increased mileage, and gave us a very noticeable increase in top end power. While it's likely that the next step in the evolution of Flashback F-150's fuel delivery system will indeed involve fuel injection, I'll say without reservation that I wholeheartedly recommend the 670 Street Avenger. In an era of "me too" technology and one-off "trick parts", it's nice to know that the name "Holley" still stands as a leader in the automotive performance field. The Street Avenger series only proves it.
For more information about the Street Avenger and the entire Holley product lineup, be sure to check out their website at ... www.Holley.com Follow us on Twitter at www.twitter.com/OffRoadDotCom
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