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Old January 14th, 2018, 09:09
rspayant rspayant is offline
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2.8L to 3.4L swap

New to the site, so please bear with me. If I am in the wrong spot or this question has been answered please direct me in that direction. Looking to swap my 'no power' 2.8 to a 3.4. I am interested in using the EFI on the 3.4 for reliability. What is required to keep the EFI? Probably have a lot of more questions. Appreciate the knowledge.
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Old January 14th, 2018, 14:55
lawagoneer lawagoneer is offline
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Re: 2.8L to 3.4L swap

Let's start with a little more information. What transmission do you have? 2 wheel drive or 4 wheel drive? What year is your XJ, different years the 2.8 had different issues.
I'll assume for now yours has a carburetor. If possible I would get the engine, computer and harness from the same vehicle, if you have 2 wheel drive the transmission as well, and swap it into your XJ. Since you currently have the 2.8 in it what ever transmission you have should physically bolt to the 3.4, I'm just not sure if the engine computer has any control over the transmission. If you have the manual trans you're light years ahead of the game. The are differences in flywheel balancing between the 2.8 and 3.4.

I did some reading and a lot of the s10 and camaro guys say to use the Holley Pro-Jection tbi system with the swap. Google "Chevy 2.8 to 3.4 swap" for all the info you'll ever need. Here is on link I thought was good http://www.lunghd.com/Tech_Articles/...Project_XJ.htm

Last point the 3.4 came as rear wheel drive and front wheel drive, make sure you get a rear wheel drive motor.
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Old January 16th, 2018, 09:49
burntkat burntkat is offline
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Re: 2.8L to 3.4L swap

The 3.4 is a more or less bolt-in swap for the 2.8, physically. It was designed as such, to give the GM F-body and S10 a bit more pep.

Going from carb (I assume) to EFI is a bit more complicated. You will need the ECM that came with the engine, or a compatible one (this gets into finding a source for the ECU with the same engine/transmission as what you're going to be running, as well as the appropriate CALPAK in the ECM to enable it to work properly. Not trivial.

You will also need an EFI wiring harness for the same, as above.

This is not a trivial upgrade. You will need in-depth electrical knowledge, the ability to read and comprehend schematic diagrams, the ability to solder well (DO NOT use crimp connects for EFI systems- too much loss), and so on.

You'd be time and money ahead to upgrade the engine and keep the carburetion. What you are doing is going to be almost as involved as stuffing an entirely different motor in there. The only thing you have going for you is you can use the same motor mounts.

I speak from experience, having upgraded a Fiero 2.8 to 3.4 with differnet EFI, installed a SBC 5.7 in a S10, and a few other swaps. I mean no ill will when I tell you, if you have to ask these questions, you're NOT ready. Congratulations on your ambition, but I'd advise swapping the 3.4 in with carby for now, run that for a bit, and undertake research to go EFI when you are ready (and have something else to drive).

Also, FYI- the upgrade to the 3.4 for reasons of economy is a fool's errand. More power is slightly less so. EFI for reliability is more of a grey area- do you often travel in conditions where the carby gives you probems (angles and dangles, large changes in elevation and so on)? If so, EFI is the way to go. But for DD to get back and forth to work, a carb, properly tuned, ought to be just fine.
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-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s

Last edited by burntkat; January 16th, 2018 at 09:53.
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Old January 16th, 2018, 09:55
burntkat burntkat is offline
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Re: 2.8L to 3.4L swap

Quote:
Originally Posted by lawagoneer View Post
Let's start with a little more information. What transmission do you have? 2 wheel drive or 4 wheel drive? What year is your XJ, different years the 2.8 had different issues. .. etc.
Great points here. Also, realize if you swap from auto to manual, or the other way around, you will need a new steering column. I know this makes utterly no sense, but it is the case with GM columns.
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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Old January 16th, 2018, 17:06
Green Mesa XJ's Avatar
Green Mesa XJ Green Mesa XJ is online now
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2.8L to 3.4L swap

Great advice. There are write ups on keeping the 95 Camaro electronics, PCM and harness. Itís is involved but doable.

Far as power out of the carburetor setup, edelbrock has upgrades for the intake manifold and adapters for factory carburetor or Weber, or Holley 4 barrel. The factory carb is junk, and the intake is not much better.
Exhaust is the next best upgrade but the XJ/MJ header kits are long out of production, possibly a s10 header kit could be adapted.

Most people who do upgrade to EFI say it is noticeable difference. However just upgrading to the 3.4 is a noticeable power increase. With a good carburetor itís much better engine than factory 2.8.


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Old January 18th, 2018, 11:07
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1990JEEPXJ 1990JEEPXJ is offline
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Re: 2.8L to 3.4L swap

Quote:
Originally Posted by burntkat View Post
Great points here. Also, realize if you swap from auto to manual, or the other way around, you will need a new steering column. I know this makes utterly no sense, but it is the case with GM columns.
Is that only for the steering wheel lock when in park feature? Or pressing the brake to get out of park stuff? Because neither of those features work on my xj and it doesnít effect anything. Itís a gm column too. Obviously if heís got a column shift or wants one, then yes he would need to swap
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Old January 19th, 2018, 06:09
burntkat burntkat is offline
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Re: 2.8L to 3.4L swap

Quote:
Originally Posted by 1990JEEPXJ View Post
Is that only for the steering wheel lock when in park feature? Or pressing the brake to get out of park stuff? Because neither of those features work on my xj and it doesnít effect anything. Itís a gm column too. Obviously if heís got a column shift or wants one, then yes he would need to swap
I believe that is the caase. It's been about 20 years since it was a big concern for me- an old Fiero project.
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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