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[jjwalker]

(originally posted by T Man)

I found this on my endless search for 2.8 info. All sounds pretty good
-Tom


Changing A 2.8L TBI To A 4.3L TBI

This article assumes that you know basic mechanical practices and are comfortable removing your engine components and reassembling them. The intake manifold, rockers, pushrods and valve covers will all be removed for this procedure and will require reassembly with new gaskets. Also some belt driven accessories electronics and vacuum lines will also be removed and reinstalled. There are a couple versions of doing this swap. One: You have a 2.8L in your truck and need more air flow. Two: you did the 3.4L swap and need more air AND fuel. In the first instance you are going to change to the 4.3L throttle body and keep your current injectors. In the second case you are going to change to the 4.3L throttle body and also use the 4.3L injectors. Either way the procedure remains the same except for a few extra steps for the 3.4L process.


Some things to keep in mind when hunting. ALL GM TBI units that were 2 barrel (2.5l was a 1bbl. 2.8, 4.3, 305, 350, 454 were 2bbl) have the same bolt pattern and the same body. Things that were different were the bore sizes and injectors. 2.8L has a 1 3/8" bore, 4.3, 305, 350 have a 1 11/16" bore and the 454 has a 2" bore. Each engine has a different injector that flows a different volume but all fit the same and are interchangeable. The TPS sensors changed in late 89 to a different style. All IAC motors were the same. 2.8L TBI units have 4 vacuum ports but all others have only 3. However, they can all be drilled for the extra vacuum port because the location exists in it for all the castings. Throttle linkage also varied between models but these are also changeable. Some other rare differences also were present, some injectors had a hole drilled below the fuel pressure regulator and had the fuel fittings clearanced for a bolt to pass through which allows for the change to an adjustable regulator. But all GM regulators were non-adjustable. The regulator consists of 4 simple parts. A diaphragm, spring, spring retainer and the housing. The spring keeps pressure on the diaphragm valve which regulates flow to maintain pressure. The retainer keeps the spring in position and the housing encloses the system. So now you know the basics. And now you know that when looking for a throttle body that all the 4.3L, 5.0L and 5.7L engines were all the same size. So don't walk right by the V8 trucks in the junk yard. And remember that the TPS changed in 89 so you must find one with the right style or you will be doing some splicing.

When you get your throttle body home start stripping it down and clean it up a little. Swap over all your 2.8L stuff. Why? Because you know it works and wasn't in a junkyard. If your stuff doesn't work you can take a chance on the junkyard stuff but it would be a better idea to get new stuff. A TBI rebuild kit would also be a good idea right now. Install either your 2.8L injectors or a set of 4.3L injectors depending on your application. If you found a throttle body with the same linkage as your old 2.8L your in luck. If not, don't worry. Grind the tab off the end of the throttle shaft that holds the linkage on (do this to both throttle bodies) and you will be able to wiggle off the linkage (it may take a pair of pliers). Now swap your old linkage over to the new throttle body and tack it on with a few welds. Last thing to address is the missing vacuum port. While you can splice in a "T" to the existing vacuum line on the opposite side of the throttle body it is suggested you do it right and put in a new port. All you need to do is find a small piece of pipe, 1/4" OD, and drill a hole into the casting of the throttle body and the epoxy the pipe into the hole and you have the port. Now that your throttle body is all ready to go and hopefully got a set of new gaskets and o-rings it is time to address the intake. Your intake MUST be bored out to match the 1 11/16 bore of the 4.3L throttle body. If not the throttle blades will hit the edges of the smaller intake bores and you will also be creating a bottle neck because the intake bores are still at 1 3/8" so there would be no point in doing the swap anyway. Remove the intake and take it to a machine shop and have them drill it to 1 11/16". When you tell them to do this be sure that they make the bores square to the TOP deck of the intake. The bottom and top of the intake are NOT parallel this is because the engine sits on a slope and the intake compensates for this and makes the throttle body sit as level as possible. You may attempt to do this yourself and I have herd of people just hogging out the aluminum with a die grinder. However, this produces very poor results which are usually quite a joke. So unless you have an end mill or drill press with a bit big enough, take it to a shop. When you get it back now is a good time to smooth up the casting with a die grinder and rotary file. You want to ease the transition from the throttle bores into the intake runners and also clean out the intake runners. Now clean it out really good with soap and water. Any water based de greaser works good such as Simple Green. If you can, blast it with a pressure washer. Be sure no aluminum filings are left over and get the rust (if any) out of the water passages. You can now begin reassembly

[jjwalker]

GM 60° V6 Power Tricks: Solutions for Corralling More Horses

The truck I did most of my experimenting on was a 1989 Isuzu Trooper. The Trooper first saw the 2.8L powerplant (an oxymoron on par with "military intelligence") in '89. I guess Isuzu learned something by waiting to see how the motor was incorporated into Jeeps and S10's, because they selected a throttle body injection system instead of a carb. Although easily mistaken for a two barrel carb at a glance, it remains a genuine Goodwrench part, along with the ECU that controls it
The advantage of having the GM motor, especially in an Isuzu, is that like so many things that wear the bow-tie, (and so few with the Isuzu badge) a healthy aftermarket caters to this motor. As a result I, like others, have been pleased to find that a bit of digging yields exciting results. To help put this information to work, I've organized it into a logical order in which the tricks can be applied -- I wish I had followed it. You may have already done some of these mods, and that's great. There is nothing particularly wrong with changing it up, however, I think you'll find that in this order you'll get a good initial bang for the buck, will address both ends of the motor, and will see some healthy gains. How much? All tricks combined should, with a conservative calculator, see your stable grow by four dozen ponies. That's pretty good for a motor rated for around 125 Hp stock. As for the real output you'll see that only the dyno really knows.

Trick #1: Turbo City, Holley or GM 4.3 TBI

Short of a turbo, the most notable gain to be had is from the addition of a high-flow throttle body. Good for approximately 20 hp, this simple 1-2 hour install goes a long way toward making your daily driver enjoyable, or at least less embarrassing. Mixing more air and fuel, and delivering them through larger throttle bores, the Holley 3210 provides an affordable option for many.
Turbo City reportedly makes a better product, and sells it at a better price. Their Hi-Flow TBI features some slick touches like air flow enhancement via shaved throttle body shafts. If not for the next option, this would be one to look at seriously. More affordable still, the TBI from a 4.3L GM V6 bolts right up. These throttle bodies are less than a hundred dollars at a good salvage yard, and the 2.8's ECU will handle the increased flow just fine. Turbo City's throttle body is actually built from the foundation of this GM model; they shave, tune, and polish it.
It only takes a few hours to install any of these throttle bodies, so the return on your effort is very high. These three throttle bodies are direct bolt-ups and provide excellent horsepower gains. In most cases, fuel economy will remain about the same if fuel pressure is well-regulated. With this sensitivity to fuel pressure, some have found it useful to install an adjustable fuel pressure regulator and even a pressure gauge in-line. The Holley, however, has a built-in adjustment screw.

Trick #2: Free Flow Exhaust

Exhaust options really help this little V6. A 2.25-2.5 inch diameter cat-back exhaust frees up exiting gases, letting the horses run. Two-inch pipe enhances crisp throttle response and provides top end gains. Many vehicles equipped with this motor can use headers from larger companies such as Pacesetter. Unfortunately, the Isuzus still lack a source for this important part, although CALMINI has a working prototype (be sure to contact them if your vote is for it to go into production). High mileage vehicles may benefit from replacing the stock catalytic converter with a free-flowing unit. Prices on these have really come down in recent years, and combined with new plumbing from the motor to the tip of the tailpipe, this will yield miles of smiles
Don't be fooled into thinking that you need a pre-fitted exhaust. Although available, they are often costly compared to the product a local muffler shop can provide. In either case, look for 16 gauge or thicker (smaller numbers are better) aluminized piping, minimal bends (only two bends are necessary from the cat back on '88-'91 Troopers), and an all-welded muffler with a lifetime guarantee.
Air Flow
After you've freed up your exhaust and got the TBI pumping more juice, you'll soon want to improve the air flow to the TBI. This will be descibed in Tricks 3 - 6. You'll also want to make sure you're not getting dirty air. Dirty air is bad - baaaaaad. Dirty refers both to particulates and to the smoothness and therefore the efficiency with which air flows into the motor. The Tornado product that most have heard of tries to smooth air flow and simultaneously mix fuel by routing it through directional fins. Although I have not found it to make any noticeable difference, I have been pleased with the results of a couple other tricks.

Trick #3: Flip Your Lid

A trick that addresses part of the weakness of the factory air filter housing on these engines is extremely easy, yet makes a real difference. Flip the lid of the air filter housing and resecure it with the original wing nut. This allows air to reach the filter more readily, streaming in from all sides rather than squeezing through the intake hose. The drawback is that filters get dirtier far quicker -- a good reason to consider trick #4. Another drawback is the increased engine noise, but that is a drawback or a plus, depending who you ask.
Performance gains are most noticeable at high RPM's, where the stock motor runs out of air less after the flip. Low-end response is also slightly improved. You may also notice less impressive changes in summer because the flipped lid allows hot engine compartment air to be drawn in. With estimates of one horsepower lost for every 10 degrees Fahrenheit increase, consider flipping the lid back to the stick position when visiting Death Valley trails.

Trick #4: Hi Flow Filters

Depending upon the condition of the existing air filter, switching to a reusable air filter may provide impressive flow rate increases. Reusable filters fall into two main categories: gauze and foam. K&N made the gauze type famous, and K&N makes a simple 10-inch ring style filter that drops right in place of the stock Trooper filter. K&N also has a new high-performance filter that utilizes a filter element on top, allowing even better air flow. Be sure to use K&N's own filter cleaner and treatment to take full advantage of their product, though. I'm not just repeating the party line - I did not follow their recommendations and learned the results the hard way.
Some competing companies suggest that oiled gauze filters actually diminish filtration. Amsoil is the company credited with marketing the first synthetic oil and a long-time innovator in air- and oil-related automotive products. Amsoil claims that their reusable foam filters pass a volume of air equivalent to gauze filters, while filtering damaging particles down to the 5-15 micron range. They claim that quality paper filters do capture these particles and that gauze units do not. As a result of these claims, and because I have used and been pleased with Amsoil products in the past, I switched to their foam filter. It was cheaper than a K&N filter and also provided a nice performance increase.

Trick #5: Fiddling with Filter Housings

Another way to maximize air flow is to use a larger-than-stock filter. Several approaches exist for this:
Use a cutting wheel on an angle grinder to remove the vertical wall around the filter housing, allowing use of a filter almost the same diameter as the housing. Larger diameter filters provide a big gain in filter surface area, and as a result, much-improved air flow.
Fabricate a hose intake system that securely fits the TBI and route a three-inch diameter hose to a cone-shaped filter.
Obtain a larger air filter housing from a similar motor.
I selected the last of these options, and used a much-larger air filter housing from an early seventies Chevy 402. This allowed use of a larger 14x4" filter. I made this swap at the same time as I installed the larger Amsoil foam filter, and the combination made a noticeable improvement over the smaller K&N filter, especially below 3000rpm. The key to making it all fit is Trick #12.

Trick #6: Throttle Body Spacer

The flow of air/fuel into the intake bores can be smoothed through the use of a simple spacer. Carl Barrett was kind enough to machine a batch of these in varying sizes, and there was a small but perceptible gain in throttle response. I experimented and ended up using the one inch spacer. This seems to be the maximum thickness that will fit without applying excessive torquebefore torque on the rigid fuel lines that connect to the throttle body. Theoretically, at low RPMs a lengthened passageway may induce turbulence, and conversely, the longer passageway may smooth out the airflow at high RPMs. This is a very simple modification if you have someone who can machine the spacers for you. I recommend 3/4-inch aluminum spacers sandwiched between thin-profile 4.3L TBI gaskets. Turbo City sells several different thicknesses of spacers.

Trick #7: Intake Bores

Another trick that works in conjunction with other air flow enhancements is machining the twin intake manifold bores to match the 1.68” diameter of the TBI. Leave this to a machinist with the right tools -- exactness of fit is critcal. The intake manifold also contains casting cavities, that, if nicked, wreck the part. In my area the going rate for this relatively simple task seems to be about $50.
Performance results from this trick are instantaneous as the motor begins to breathe more. Gains are particularly evident at higher RPM's when the motor was previously starving for air. Because removing and re-installing the intake is a fairly labor intensive process, at minimum, pair this trick with at least Trick #8. Consider buying a used manifold to allow a machine shop to bore it without disabling your rig.

[jjwalker]

Trick #8: Roller Rockers

The 2.8 responds well to substituting roller rockers for the stock rockers. At a bit over a hundred bucks for the basic version, manufacturers claim that switching from 1.5:1 to 1.6:1 lift ratio rockers yields about a 10% hp gain. Because the rocker arms require a removal of the valve covers, intake and TBI, this trick is ideal to link with trick #7. If you plan a subsequent cam change, you may want to stick with the stock 1.5:1 ratio, but upgrade from tappet rockers to roller rockers.


Both Crane Cams and Competition Cams make roller rockers for this motor. Crane Cams produces the affordable Magnum Roller Rocker, which I installed, as well as the Gold Race full roller rocker. At twice the price, it offers twice the zoot, using needle bearings for the fulcrum, an aluminum body, and replacement studs (the 2.8 used 10mm vs. the more common 3/8"). The full bearings certainly decrease friction, but the power gains over the Magnum are less obvious.

Trick #9: HyperTech Power Pulley

The Camaro/Firebird often upgrade their 3.4L F-body engines by installing underdrive pulleys. A replacement crank pulley and, on some motors the alternator pulley, reduce the load on the motor, freeing up a few more horses. A relatively simple trick, the gains are modest, but of enough interest to strongly consider. The drawback is that the alternator produces proportionately less power because of the underdrive pulley, which may be problematic with the current requirements of winches and driving lights.

Trick #10: Cams

Trick #8 is ideal when coupled with a performance cam shaft. A number are available for this bow-tie block, but you’ll want to keep your eye out for one that is sold with the matched lifters, valve springs and all the locks and seals. The 2.8 uses flat tappet lifters, so you must replace them too when adding a new cam. If ground to match the owner's driving profile the gains from this modification are both impressive and an improvement on the placement of the power band. Companies such as Competition Cam can work closely with you to assure that you get the ideal grind. And that's important when you're talking this much labor to get down to the cam on the 2.8L. Still, yields from the cam are also going to be in the 15% range and so any problem requiring pulling the motor is a good reason to consider a cam swap. Remember that depending upon the cam grind, any use of new roller rockers with it may demand that you not use a 1.6 ratio rocker.

Trick #11: Computer Chips

Super Chip's replacement chip proided a perceptible gain -- the manufacturer claimes 15 horsepower, but recommends using high octane fuel to reap these benefits. This chip is a mixed blessing; it is easy to install and produces tangible gains, but always does more damage at the pump. Fortunately, the chip does not reduce fuel efficiency or preclude using lower octane fuels, although some folks report an increase in motor knocking. The chip may also end up being better able to to handle changes like cams or roller rockers. The chip can also be reprogrammed to support subsequent changes, if necessary. Jet Chips also markets replacement chips for 60-degree V6s.

Trick #12: Power Charger

The Power Charger smooths airflow to the TBI.
Power Charger Installation
Hypertech's Power Charger is rivaled only by the lid flip for tricks that are easily accomplished. Mounting is very simple, as the unit sits between the throttle body and the filter housing. The result is a lifted housing as the 3" or so tall Charger lifts the housing up. In our Trooper we were forced to modify the hood reinforcements to allow adequate clearance. Were it not for Trick #6 this would likely not have been a problem
Despite the fact that our unit was meant to fit 5.0, 5.7 and 7.4L '87 to '95 Chevy trucks, it still mounted perfectly on our '89 Isuzu Trooper. In fact, the Power Charger enabled us to remove our filter housing altogether, as the 10" K&N mounted exactly on the charger's rim. This made for a really clean setup, although not without replacement of the center shaft onto which the wing nut goes. Top that off with its 50-state emissions approval and you have a nice improvement to your system. Gains on 5.7L engines have shown increases of between 5 and 8hp on the dyno.
For an alternative product consider the similar but as yet untested by the author Turbo City Air Flow Enhancer.
Because the mounting ring diameter of a GM TBI matches that of most other throttle bodies and carbs, some items can be adapted to more applications than were envisioned by their creators. Hypertech's Power Charger is a perfect example. The product, which serves to smooth air flow down into the throttle body, is shaped like a bowl, and is constructed of spun aluminum. Extremely simple in nature, the Power Charger improves flow and therefore power. The results I have seen are best observed at higher RPM's as the engine strives to draw in adequate air and fuel. There, top end limits and response times are improved. Thus from 4500rpms on up the Trooper no longer struggles, but instead pulls smoothly to red line, never apparently wanting for fuel or air. These gains make it a plus for the 2.8L which has little grunt but will respond well to being wound out given a few of the previous tricks (see sidebar for more details).


MSD wiring and Power Charger.
This trick has also allowed me to squeeze in the 402 Chevy air cleaner housing and thus the 14" Amsoil filter. Because this housing has an inset bottom, it sits low over the air horn. However, its diameter allowed me to cut out a segment of the bottom slightly smaller in diameter than the top of the Power Charger. I next put silicone on the freshly cut bottom, covered it with plastic food wrap, and proceeded to squish the Charger into it. Once dry I had a perfect fit between them. This yielded an outstanding setup, both for fit, power, and cleanliness. As an added bonus it meant sound levels dropped; the open filter element allowed much more engine noise to escape. It also allowed me to fabricate an adapter to link a 3" flex hose to an ABS snorkel. This modification offers a really nice improvement, as it not only means the engine draws in all-important cool outside air, but it also allows for cleaner air. It accomplishes this through placement (on the roof) and through use of a Centri precleaner. Made for industrial machinery facing dusty air conditions, the Centri uses centrifugal force generated by the engine's induction to throw off particulates, including water, bugs, dust, etc.

Trick #13: Electric Fan

Like the Power Pulley, the use of an electric cooling fan in lieu of the mechanical stock fan in the 2.8 can free up the motor to work on moving you along. Replacement with a quality electric fan such as Flex-a-lite's Black Magic will give a few horses back to the rig. While fit can be tight, the result is a fan that doesn't need to always come on. If you ever tangle with deep water crossings this is yet another reason to consider this trick. However, if you live in the heat of the South and do much crawling this may not be suited for your needs. Consider upgrading to a dual core radiator in the process.



The Flex-A-Lite electric fan will free up some power from the motor Here is a close-up of the MSD 6 Off-Road ignition upgrade

Trick #14: Ignition Upgrades

A number of performance ignition systems are available for the 2.8L. Typically they will be matched to plug wires, a performance coil and, sometimes, rev limiters. For trail usage and to address lugging at low RPM's, a zone where these motors show their lack of grunt, I chose the MSD 6 Off-road. It is virtually a plug-n-play application, is compact and is offered with an adapter specifically for the GM components. I also got their HEI replacement coil and the massive 8.5mm Super Conductor wires. For all this I have gotten just what I expected; a lack of low end stumble thanks to the dual spark below 3,000rpm, and an easy to install product.

Trick #15: Cooling through Ceramic Coatings

Ceramic coating on some of the engine parts helps keep down the heat under the hood
Cooling the motor, as stated earlier, can only lead to more performance gains. A unique way to achieve this is through the application of ceramic coatings. This process of professionally sprayed and baked-on finishes not only improves looks but also helps retain heat so that it can be passed out of the engine and engine compartment. Treating of exhaust manifolds and headers have been the most common uses to date. However, other parts can be done as well due to the thinness of the coating. My own use has been on valve covers, intake manifold and headers, and was done by Performance Coatings. Obviously this trick should be considered in conjunction with other changes to avoid redundant labor and to maximize performance gains of each upgraded component. Performance Coatings' finishes are very durable and are available in a wide range of colors.

[jjwalker]

On the Horizon
There are a lot of little ways to improve the performance of the GM 2.8, and some are more effective than others. Some tricks should be coupled together to reduce labor, but many are simple do-it-in-10 minutes procedures. This is good news for a group of owners who have long-endured tired old iron and can't wait another minute to see things improve.

Conclusion
There are a lot of little ways to improve the performance of the GM 2.8, and some that are more effective than others. Some tricks should be coupled together to reduce labor and/or gains, but many are simple do-it-in-10 minutes procedures. This is good news for a group of owners who for so long have endured this tired old iron and who can't wait another minute to see things improve.

If you are looking to more serious improvements, shell out $17 or so for Tom Currao's How to Rebuild Your GM V-6 60° Engine. For more tricks on power, read Chevy Power -- though it includes only one chapter on the 60-degree motor, it is still a worthwhile read. Also plan on investing in one or more manuals on your vehicle (e.g., Chiltons or Haynes).
As a word of caution though, the net gain from all of the above changes may yield increases of as much as 50hp, but much of those gains are occurring at the higher rpm end of the spectrum. That said, the real question may just come down to whether the power needs of an owner are on par with the potential of these different alterations. If the answer is no, then the options become that much clearer: live with it, get a new rig, or install the 3.4L V6 that GM provides as a replacement for the 2.8L, or better yet just get one from a ‘93 to ‘95 Camaro or Firebird. But that is another story altogether. And a whole different power range as well.

[jjwalker]

Special thanks to T Man for finding and posting these articles!

[T Man]

you are very welcome. btw, where did this come from? i thought i had posted it here

[jjwalker]

yeah, you did, but I took them and made them one big sticky thread to uncludder the front page, then deleted the individual posts.

I am trying to avoid a front page of just stickies if you know what I mean.

[T Man]

i see ok, whatever