Some of you will
remember reading the article “Holley’s
Cure for the Carburetor Blues” here on Rockcrawler.com
last year. You may also remember me wishing for a larger Truck Avenger
to go with my “warmed over” AMC 401. Well, that wish
has come true! Holley has begun producing the new 770 CFM Truck
Avenger carburetor, which is 100 CFM larger than the original!
the 770 CFM version looks almost identical to its younger brother.
It has all the off-road modifications just like the 670, such
as the one-piece fuel transfer tube, clear fuel level sight plugs,
spring-loaded needles and seats, etc. The only difference I noticed
was a large vacuum port had been relocated. Other than that, you
won’t notice any difference until you check out the size
of the bores or “barrels.” As you can see in the photos,
there is a significant difference!
Unlike the changeover from an old QuadraJet to the 670 Truck Avenger,
the process of installing the 770 took all of 15 minutes, since
everything hooked up just like the 670. If you’re swapping
from a QuadraJet (or another carb, for that matter), be sure to
check out the article referenced earlier. It will save you considerable
time depending on your application.
I cranked the engine over to fill up the fuel bowls. Before I
could even pump the accelerator to give my 401 a squirt of premium
and set the choke, the engine fired and fast-idled at about 1,500
rpm. I let it warm up a little while checking everything under
the hood, and tapped the throttle to knock the idle speed down.
The engine came down to a pre-set 900 rpm or so and I then adjusted
curb idle speed to 700 rpm where I like it. I messed with idle
mixture just a bit, but found myself putting it right back where
it was when the carb came out of the box!
looking up to snuff, I installed my Holley PowerShot air cleaner
and headed out for a little on-road testing.
It was like this carburetor was made just for my engine! It worked
well in every aspect, from light to hard acceleration. One thing
to note, was I had switched out the spring for the vacuum secondaries
to the lighter one (as I had on the 670), which allows them to
open sooner. On the larger 770, they came in a bit too soon. Switching
back to the heavier original spring worked well. Compared to the
670 Truck Avenger, the 770 definitely has the edge. Compared to
my old QuadraJet, the 770 is about neck and neck, especially when
you put your foot flat on the floor. Off-road however, the Truck
Avenger, either the 670 or 770, leaves the QuadraJet in the dust!
My first opportunity to test the 770 CFM Truck Avenger was at
Barnwell Mountain Recreation Area
(BMRA) near Gilmer, Texas. I put the carb through its paces -
extreme off-camber positions, steep inclines and declines. I put
my CJ-7 into an extremely off-camber ravine, scraping the right
rear fender flare in the process with not one hiccup.
decline operation was tested on the Fun Country and DeWoody trails.
Fun Country is a level 4 trail (on a 5 scale) with a good ledge
near the top of the last hill climb. With the exception of bending
my driver’s side mirror (which was folded in!) on the tree
you see in the picture, I made the climb with no problem. In fact,
at the top, a fellow Jeeper asked what kind of fuel injection
I was running! I thought I was going to have to raise the hood
to prove it to him! (Please note: The tree you see in the picture
was left standing intentionally as a safety measure to catch vehicles
that might get sideways on the ledge as part of the trail building
a 5 rated trail, (which is really just a very challenging hill
climb with numerous ledges on the way up), things got a little
more interesting. I ended up winching up the last few feet, after
I put the front tires a foot or two in the air on a ledge. This
had nothing to do with the Truck Avenger, just my driving style!
Even the rough terrain and the extreme angle didn’t stall
the engine. While I was sitting waiting to get hooked up to the
cable, the engine did begin to run a bit rough, but I was sitting
at a good 45+ degrees! I had no problem keeping it running, though.
On hill climbs, rough terrain and off-camber ravines, the 770
CFM Truck Avenger performed just as well as the 670 CFM version,
which is exceptional. For sand or mud, there’s no question
the greater CFM will come in handy. While I wouldn’t replace
a fuel injection system to run any carburetor, there’s no
doubt in my mind that the Holley Truck Avenger carburetor is the
closest thing to fuel injection you’ll find! The toughest
choice you’ll have to make is which one to get, the 670
or 770. If you’re running a stock 350 cubic inch or smaller
V-8, I’d recommend the 670 CFM model. If your engine is
modified or you’re into the bigger cubes (like me), the
new Holley 770 CFM Truck Avenger is for you!
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