Reviewer's Notebook
2.8 V6 Power Solutions
Holley 3210 Throttle Body Injection

Authors: Sean Michael, Jason Brown, Doug Wolfe, Dan Dalton
Editor: Randy Burleson

Holley's two-injector 3210 Throttle Body Injection System looks almost too good to hide under the Trooper's air cleaner.
The GM 2.8L 60 degree V6 is notorious for its lack of power. This motor was the standard power plant for some of the most common mid-sized 4x4s, including S-10 pickups and Blazers, Isuzu Troopers, and Jeep Cherokees. There are a ton of mid- to late-Eighties versions of these trucks with aging engines that leave you wanting... wanting more power, and wanting an affordable means to gain it. If you own a rig with this engine, you know just what we mean.

There are a variety of inroads to improved performance with the 2.8. A cat back exhaust frees up the gases, as does a header. Installing a high-flow K&N filter can yield a nominal improvement, but these changes may be more apparent to the psyche than the dyno. Plugs or other minor changes have similar effects. Performance chips can give more dramatic effects for those with fuel management computers. Installing a cam with a different profile can have much to offer as well, but cost is high and installation is complicated. That leaves the carburetor or TBI.

Aftermarket carburetors were available, but for throttle bodies, only high-end, custom systems were available. That changed when Holley released its line of Pro-Jection fuel injection systems. Holley offers its 2 barrel 400 cfm 3210 (model 502-3) for the 2.8L V6. A direct bolt-up swap for the stock throttle body, the Holley unit offers 48% greater flow area through the bores (1.680" diam.), and increases engine ouput by more than 20 estimated horsepower. It does so with the historic Holley quality in parts and design, and can be fitted to '85.5 - '89 Chevy/GM trucks (Note that earlier years with the carb used a different intake manifold), as well as pre-'92 Isuzu Troopers with the same engine. Further, it has been successfully installed on this V6 as it appeared in Jeep Cherokees.

Don't expect much cooperation, knowledge, or sympathy from Holley Technical Service or retailers if installing the 3210 on an '88-'91 Trooper. Holley's official stance is that it will not work. Our experience is that it does work -- and work well.

Similar dissuasion may be experienced by Jeep owners, however we have not performed that install.'s Jeep Section has an article that addresses installing a Holley throttle body injection system on '79-82 Jeeps with the 258 at:


Wire Color
New Unit
Old Unit
Green Blue
Red Green
White Black with blue stripe
Blue Black with blue stripe
One of the best things about the Pro-Jection system is the ease with which it can be installed. Tools in hand, this is a 1-2 hr swap for most semi-savvy wrench-wielders. A brief though sufficient page of instructions describes installation. Following removal of the air cleaner and housing, disconnect the various lines and wires from the stock throttle body. Carefully label the injector control wires, and then unbolt the stock unit. Remember, connecting the wrong wires may damage the ECM, so take the time to double-check and get it right. The table at right lists the wire connections for Troopers.

We spliced the injectors wires with quality heat shrink wrap connectors, rather than Holley's crimp style butt connectors. This offers an additional margin of protection against moisture.

Thoroughly clean off the old gasket before installing the new one, plugging the intake to prevent errant gasket pieces from falling into the intake manifold. Remove the fuel fittings from the stock throttle body. When reattaching these fittings to the Holley throttle body, use the new 'O' rings, and be sure they "pop" in when the connectors seat.

This shot clearly shows the 'z' bend we used to make the air cleaner stud work w ith the Trooper's air cleaner housing.
When all is in place and wired up, thread in the provided air cleaner stud. On the Trooper, it doesn't align well with the air cleaner lid. A bit of bending makes it work, though it is still a bit too long to allow the wing nut to spin all the way down to the air cleaner lid. We used a beveled rubber gasket to seal this gap, preventing moisture and/or dusty air from being sucked in around the wing nut. We found it at our neighborhood hardware store in the little bins near metric fasteners and all the other odd small hardware items.

After completing installation, follow the initial startup steps, which are clearly outlined in the instructions. These steps reset the computer. Don't be alarmed when if the first spin around the block doesn't show performance gains. All four authors experienced a "settling in" period that lasted a few days. Once the computer learns the new engine characteristics, the grins begin.


Once the ECM figures out what is happening, the newly-equipped engine produces, as one author put it shortly after the install, a "seat of the pants ride." The Holley system seems to have lifted an invisible barrier to horsepower, freeing the needles to move clockwise at noticeably improved rates. Holley's claimed increade of more than 20 horsepower is easy to believe. Upwards of 3000 rpms, the motor pulls and pulls, seemingly ravenous for more of that delicious air/fuel mix. The tach moves rapidly toward redline and grins abound!

Unlike the high end, gains in low end performance have been nominal if not unrecognizable. As such, the Holley appears to be most beneficial for pavement driving and off-road wheeling spent in high range. This situation may change as we make upcoming modifications to the intake after the TB. Again, the Holley seems to be wanting for more air, and low rpms apparently do not yield the cfm necessary to make things take off.

We have each registered significant decreases in timed acceleration runs. Times for 0-50 mph runs dropped from a range of 10.5 to 13 seconds to a range of 9.5 to 11.5 seconds. Accelerating in 4th gear from 50 to 60 mph registered a drop of 2 seconds on average. These times were generated using a variety of octane levels, however we noticed somewhat better performance with the higher level fuel. This may be explained in part by the fact that some of us are using performance computer chips which yield more hp with increases in octane.

Fuel injection means no stutters or stalls on steep angles.
An advantage of any fuel injection system used for wheelin'--consistent fuel/air mixing on steep slopes--has proved to be no less present for the Holley than it is in the highly reliable stock throttle body. The Holley has given zero problems when operated on the steep stuff, its performance a reminder of the advantage of more highly evolved fuel systems. No stalling, no stuttering, and flawless firing up when nothing but sky is seen through the windshield.

Other performance improvements have been seen in mountainous driving, where dipping into 3rd gear is now needed far less. For those with the indecisive 4L30E automatic transmission, the tendency to downshift when pulling small grades is reduced. Towing performance has also seen a significant improvement after installation of the Holley. Unfortunately, the power comes at a price. High load driving, such as the latter situations, demonstrate the TB's ability to send a lot of fuel down the 2.8's throat. Fuel mileage dropped appreciably in those situations. Whereas flat land driving tended to remain about the same (15-18 mpg depending upon the rig's weight and drag inducing accessories such as racks), high load and around town driving saw mpg drop. Low marks were seen at 10 mpg on the porkine, accessory-festooned Project WomBAT, although 13-15 was more typical for others.

We have also experienced symptoms of an overly rich fuel mix (blackening of tail pipe, smoke) since the install. This makes sense when one considers that Holley recommends an in-line fuel pressure gauge be installed ahead of the TB. Available for around $50, this is a modification that we will be trying in the near future. (see future sidebar). Once that is installed the fuel regulator may be adjusted. On the back side of the TB, behind the injectors, is an aluminum cap. Turn the adjustment screw clockwise to increase fuel, and counterclockwise to decrease fuel.

All of this has pointed to the importance of efficient air flow. Enlarged cat-back exhausts and free flowing air filters appear to realize more of the Holley's potential. We noticed some lessening of the richness problem as we 1) cleaned our K&Ns, 2) flipped the cleaner housing lid and 3) replaced worn spark plugs. [For a more thorough discussion of Holley TBI tuning, one should consider a book on their carbs and injection systems available from HP Books.] Finally, advancing your timing may be an option to consider, it having worked well for a few of us.


The Holley Pro-Jection throttle body for the Chevy 2.8 V6 is an outstanding means by which to improve this motor's anemic performance. Available for under $300 from performance wholesale outfits, this TBI is a simple install. Though it tends to yield 2-3 mpg loss, any such decrease is well worth the hp gains, and occurs by-in-large under low gear and high load driving. More performance gains promise to be had with some simple air flow enhancing modifications that are on the slate (see upcoming articles). Without those modifications, power gains remain most apparent above 3000 rpms, thus making this TBI more of a benefit for pavement pounding than rock crawling. However, for boxy rigs like Isuzu's Trooper, that is precisely when the power is needed most. And ooooh does it feel good. So thanks to Holley, its damn the head wind, full speed ahead!

Holley Performance Products
1801 Russellville Road, Suite ORC
P.O. Box 10360
Bowling Green, KY 42102-7360
Dealer Locator: 1-800-2HOLLEY
Tech Service: (502) 781-9741

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