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
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!
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.
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!
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.
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.
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
the way, anyone want to buy a good used Quadra-Jet?
1801 Russellville Rd.
Bowling Green, KY 42102-7360
782-2900 or (270) 781-9741
Brinks is an avid four-wheeler and a contributor here
at ROCKCRAWLER.com. Jack resides north of Houston,
TX and frequents many events in the Southwest.
Jack at email@example.com