Holley Truck Avenger Off-Road Carb
& Power Shot Air Filter
By Jack Brinks

 

ROAD TESTING:
Before heading to the trails, a little testing on the road was in order. I was interested in comparing the Truck Avenger to my old Quadra-Jet. My initial tests involved starting from a stop and mildly accelerating through the gears, without kicking in the secondaries. Here, I would have to give a slight advantage to the Holley. I feel this is due to larger primary bores in the Avenger.

The big difference, though, was when I hit the four barrels. The vacuum secondaries in the Truck Avenger kicked in smoothly, unlike the Quadra-Jet. This is not really an apples to apples comparison, considering the difference in CFM ratings, however. Holley provides a lighter spring for the vacuum diaphragm to allow the secondaries to open a bit sooner, which worked out well on my engine. The neat part is that it takes all of 60 seconds to switch springs!

For those not familiar with a Quadra-Jet, it has fairly small primary bores - about 300 CFM, and VERY large secondaries - around 500 CFM. With this design, if not set up just perfectly, many drivers will experience the Quadra-Jet "bog" when those huge secondaries open up. This setup is good for high RPM operations, but as I've said, that's not what I'm in to. It is fun to floor it every now and then, though.

Anyway, now that the initial testing was out of the way, I began to drive more aggressively, accelerating quickly from a dead stop. When doing this, I experienced a hesitation or bog, right after initial acceleration. After verifying that the accelerator pump was giving a good shot of fuel, I headed back home and called Holley Technical Service. They quickly confirmed what I had diagnosed; although everything was working as designed, I just wasn't getting a big enough squirt of fuel to make my 401 happy. After a short discussion regarding engine specifics, power valves and re-jetting, they felt that the way to go was to increase the size of the accelerator pump nozzles, which are changeable on the Truck Avenger by removing a single screw. The standard size is .028", which is fairly small but adequate for most engines. Since we couldn't be sure which size we needed, Holley sent me several sizes - 0.31", 0.35", 0.37", and 0.40". After experimenting with different sizes, I finally installed the 0.40" nozzles with satisfactory results. Chalk one up for Holley's tech support!

OFF-ROAD TESTING:
This testing was done at a new off-road park called Katemcy Rocks near Mason, Texas. This 900 acre park has been dubbed "Son of Moab" or "Mini-Moab" by some because of the awesome traction afforded by the granite rocks. Like Moab, this place is very unforgiving, and the carnage is usually considerable. The list of broken axles, rings & pinions, u-joints, and rollovers is too extensive to go into here. If you get a chance, check out their site and visit the park.

I put the Jeep through every situation I could find, including steep inclines, off-camber spots, drop-offs, & rough terrain two-tracks. I can't tell you that I went everywhere I wanted to, but what I didn't climb wasn't because of the Truck Avenger! Even while climbing uneven inclines of over 45 degrees, the carburetor never gave any indications of trouble. Even though I don't care much for extreme off-camber spots, I almost put the Jeep on its side a couple to times during testing to make sure that it kept runnin smoothly. At over 30 degrees, the engine never stumbled.

I also ran the Jeep over some pretty good-sized rocks at much greater speed than I would normally to try in order to induce problems. Here, I noticed a little stumble, but no indication that the engine would stall. In fact, contrary to life with my Quadra-Jet, the Truck Avenger never stalled my engine or failed to take me where I should go. I didn't make it up The Wall, the near-vertical climb shown in the photo, but the engine kept running fine as the left front tire went 18" in the air, according to the spectators. Wisely, I think, I slammed the clutch in after the third strike, and took the bypass. The Rat Hole was interesting, with a Jeep having done a backwards roll off of it the weekend before (If you look close, you can still see some glass left-over from the hard top). The Truck Avenger took my Jeep up and over this 50 degree climb with ease, and through the off-camber spots on the other side.

The Holley Truck Avenger definitely performed better than my Quardra-Jet and much better than I expected it to. In fact, the rumors are that some of the improvements Holley has made in the Truck Avenger will find their way into their Street Avenger version because they work so well. Now, if they would just make a 770 or 870 CFM Truck Avenger...

By the way, anyone want to buy a good used Quadra-Jet?