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post #1 of (permalink) Old 01-31-2000, 03:38 AM
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Where to turn to modify 2.8L V6?

I've got a '91 S-10 Tahoe 2.8L V6 that I'd like to modify to basically get more power out of it. I like the small engine because of the gas mileage, but want it to be quicker. What can I do to get more out of this engine (bolt-on or overhaul)? Does anyone make aftermarket performance parts for the 2.8L V6's?

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post #2 of (permalink) Old 01-31-2000, 11:27 AM
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Re: Where to turn to modify 2.8L V6?


Holley makes a 400 cfm throttle body that mates to the stock manifold.]
Edelbrock makes a two piece manifold
Crane cams offers 2 or 3 different cams for the 2.8
Jegs (www.jegs.com) catalog has all of these things.
also try J.C Whitney, just look for brand names when you buy. they offer pistons, rings, gaskets, timing sets, caps,rotors, and alot more.

an Msd ignition (6a i believe) works with the 2.8 when used in conjunction with the simple wiring harness they offer.
the Blaster 2 GM coil adds power, but i dont know if that'll fit your application.......


post #3 of (permalink) Old 01-31-2000, 01:05 PM
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Re: Where to turn to modify 2.8L V6?

If you go for the higher voltage coil, you'll probably have to be changing cap and rotor every 3-6k miles... [img]/wwwthreads_images/icons/crazy.gif[/img] Also, to get the benefit out of the more powerful coil, you'd have to increase your spark plug gap... There's no set rule as to how much, just play around with it until you get the most benefit... [img]/wwwthreads_images/icons/wink.gif[/img]


[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 6" lift, 35x12.5s & '85 GMC S15 4x4
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post #4 of (permalink) Old 01-31-2000, 11:23 PM
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Re: Where to turn to modify 2.8L V6?

If you use the Holley, be sure to bore the holes in the intake manifold to match the larger-sized bores of the Holley. Adds a lot of performance over the Holley's step-down gasket. BTW you can use a GM 4.3 TBI of the same vintage, used a lot cheaper than the $315 Holley.

Have a 2-1/4" or 2-1/2" free-flowing cat and exhaust installed at your local muffler shop. Use a K&N air filter along with the Big-Bore TBI, and if you have enough clearance under the hood (and don't mind the increase in noise), turn the lid on the air cleaner housing upside down -- it will flow a lot more air.

If you don't want to tear into the cam, you could install a set of Comp Cams Magnum roller rockers. The 1.6:1 ratio is greater than stock (1.52:1) and adds lift.

I did all these mods to my '90 Trooper with GM 2.8, and it made a very noticable difference in power and driveability. And when drive reasonably it still gets good mpg (sometimes even better than before).

Hope this helps.....ed

post #5 of (permalink) Old 01-31-2000, 11:43 PM
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you put a 4.3 throttle body on a 2.8?
all the sensors and injection b.s hooked up?
where could i get a throttle body and a gasket?
and how much did the Tb swap cost (im assuming it was from a junkyard...)?
are you positive it would work correctly, even on my '88 S-15?


post #6 of (permalink) Old 02-01-2000, 08:16 PM
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Re: 4.3TBI

I didn't do it, but one of the guys at the ITOG site who did the 3.4 swap in his Trooper put a 4.3 TBI on. From what I recall he got a used one from www.car-part.com for around $50.00. Another guy posted that he could get a remanufactured unit for around $75.00. Either way a lot cheaper than the Holley. I have the Holley, got it from Jegs for around $300 but that was last year; they are around $315.00 now. After some research I realized that the 4.3 TBI had the same exact bore size as the Holley unit. I went down to the local auto parts store and asked for a base gasket from a '90 S-10 with a 4.3 TBI. Lo and Behold, exactly the same bolt pattern and bore size!

When John G. over at ITOG put the 4.3 on, he said there were minor differences with the throttle cable bracket, and he had to use the 4.3 bracket to make it work right. Also, the year 4.3 TBI he got (a '92 I think), had a different style Throttle Position Sender unit, and the connector plug was different. All he did was go to the wrecking yard and pull the plug off of a wrecked Blazer's wiring harness and adapt that to his 2.8 harness. Same number of wires, just a different style of plug. Also, he said that they did change the TPS on the later models, so maybe if you found a 4.3 TBI the same year as your rig it might have the same style of equipment. The injectors and all the other lines/connections hooked up just like the 2.8 TBI.

With the stock 4.3 base gasket as a template, you can mark the holes and have a machine shop bore out the manifold for you. There is plenty of meat in the intake, and no water passages are near enough to bother with when boring the holes. Either the Holley or the 4.3 TBI will bolt right down on this modified intake with no problems. I imagine if you didn't bore the holes out, the throttle plates of the larger-sized TBI would hit the intake when you gave it the gas. This is why Holley includes a funky adapter gasket about 1/4" thick, which transisitons from the Holley to the smaller holes in the 2.8 intake.

Of course this limits the airflow somewhat but it does make installation easier since you're not pulling off the intake to have it machined.

So if you spring for a used 4.3 you'll have to bore the intake, since I don't think you can get the step-down gasket separately from Holley.

The Holley has higher-flow injectors than the stock 2.8, and the computer adjusts for the correct air/fuel mix once it's in closed loop. The Holley does have the advantage of having an adjustable fuel pressure regulator, if you need to lean it out a bit or richen it up. Most stock 2.8's will run a bit rich with the larger TBI. With various mods that make the engine breathe better, this is not so pronounced. My tailpipe on my Trooper is usually sooty, and you'd think it's running way too rich, but it was getting almost 20 MPG on the hiway last summer. Not bad for almost 4000 lbs and 4:56 gears! I expect that the injector flow rate in the 4.3 TBI is real close to the Holley's, and that's why it will work with the 2.8 EFI setup.

And if you ever swap to a 3.4, the larger TBI makes it run even better. The extra airflow demand leans that puppy right out, too!

Anyway, hope all this helps you decide which way to go. Post with any other ques you may have. good luck.....ed

post #7 of (permalink) Old 02-01-2000, 09:06 PM
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What's ITOG? what is the stock 2.8 tbi bore? what is the 4.3 bore? does the 4.3 tbi bolt to the stock holes in the intake? will it really add performance? if i do this conversion, im gonna get the 4.3 TBI riser plate from Jegs.....it add hp and helps throttle response reportedly. if you know anyone who could give me details on this swap, i would appreciate the info.......


post #8 of (permalink) Old 02-01-2000, 11:35 PM
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Re: 4.3TBI

ITOG is the Isuzu Trooper Owners Guild, www.itog.com

ITOG has a real good discussion forum, we have gone over a lot of 2.8 V6 performance issues, and also quite a few of the members have successfully completed the 2.8-to-3.4 swap. So we have already worked out a lot of the kinks. You can go to the Discussion Forum (and the Archives) and do a keyword search for topics such as "3.4". You'll get a lot of posts that may have info you could use.

Check out this article at Off-Road.com for a look at the installation of a Holley Big-Bore TBI into a 2.8 Trooper:

http://www.off-road.com/isuzu/womb_tbi.html The part about the injector electrical connector may not apply to you, as the Trooper probably has a little bit different wiring harness than the S-10.

About the bore sizes, I don't remember the exact diameters, but you could get a 4.3 base gasket at the auto parts store and compare it to a 2.8 gasket. The bores of the 4.3 are quite a bit bigger and they definitely flow more. Note: the bolt patterns on the 2.8 and 4.3 TBI's are identical; the 4.3 will bolt rightr up to the 2.8 intake. However, it will NOT work unless (1) you bore out the intake holes for clearance and better airflow or (2) install some kind of spacer/gasket. If you don't bore out the intake, a spacer will not help as much as you think, since there will be an abrupt transition from the larger holes of the TBI to the smaller inlet holes in the intake. That is why Holley provides that adapter gasket with their TBI. It has beveled edges which are larger where it fits against the TBI and smaller at the manifold side.

Also check underhood clearance before installing a spacer -- with 3/4" of spacer, my air cleaner hit the hood of my Trooper and broke the air cleaner stud when I flipped the lid. I'm not sure but I think the Blazer/Jimmy is tigher under the hood than my Trooper.

As far as performance goes, it certainly does make a difference. However, if everything else is stock on your rig, you may not be happy with it. You need the other mods we discussed (exhaust, intake, cam/rockers, timing, etc) to get the full benefit of the increased breathing. At a minimum do the exhaust mods first, to uncork the engine. It doesn't matter how much air you can pull into the motor if ]you can't get it out! Have Fun......ed

post #9 of (permalink) Old 03-15-2011, 11:40 PM
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can the 4.3 injectors be ran in the 2.8 throttle body?
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post #10 of (permalink) Old 04-06-2011, 06:50 PM
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WOW!! - a decade old post....talk about beating a dead horse!!! LMMFAO!!
To answer your inquiry, yes the 4.3 injectors can be put on the 2.8 TBI; but it's possible to adapt the 4.3 TBI in place of the 2.8 TBI, with some splicing.

I need a bigger engine!
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