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CAJUN YJ 05-15-2013 08:19 PM

5.7 Vortec swap
The old 4.2 finally crapped out..... I was able to pick up a 98 gmc z71 as a donor truck. Motor isn't running, which I will rebuild, tranny an all the rest of power train is good.
What do I need to keep off of the donor to put into my yj?? I know the computer for sure, but besides motor, what else????
Going to be my first motor swap so any advice would be great! Anything I should look out for or tricks to mk it a lil easier???
Also I'm going to attempt the 350 rebuild myself. Any tips?

Nubby55 05-15-2013 09:01 PM

Tips on the rebuild, have all your machine work done at Greenlee's engines in B.R., i've use them for 40 years and you can trust what they say and do!
Allso study and read all you can be for you start, don't take short cuts, an engine is only as good as the man working on it.

Where are you, in Coon-Ass Country! :wavey:

CAJUN YJ 05-15-2013 09:27 PM

Lol nice to hear from a fellow coonazz! Lol I'm down 20 min south of Lafayette.

indirocz28 05-16-2013 07:06 AM

Plenty of people have done V8 swaps.

The issues you will have anyway are the gauges and wiring, but it just takes some time not really a huge deal. The YJ with the 4.2L can be easy to work with as far as factory gauges and things due to older technology. There are plenty of posts here on the forums and internet. Google is your best friend.

I put a TBI 350 into my 1990 YJ and wired it all up. Ran like a top.

The most important thing is for you to take your time. Do stuff right, and expect it to cost a good amount for parts. Don't expect this to be a $300 deal. You will need a radiator also. Which can be found on E-bay for $175-$500.

Look at Novak Conversions or MORE for motor mounts. Most people recommend MORE over NOVAK or Advance Adapters.

Do your research.

Like I said. Take your time. Go fuel injected so that you have technology, and better mileage on your side. Do it right the first time. Not like the guy did who initially put a SBC in my first YJ.
Link Below:

Currently working with a buddy to put a LSx 5.3L into a 2000 TJ with all NOVAK parts.

CAJUN YJ 05-16-2013 08:23 AM

Ok thanks! Very much apreciated!

I don't think my gauges will be too much trouble as I have recently swapped out all my gauges for new sunpro gauges.
Thx again!
Ill start posting pix as soon as I start! Getting very excited to do this!

indirocz28 05-16-2013 10:02 AM

Again, just make sure you take your time man. Measure stuff right and be precise.
The dumbass who welded in the 4x4 square tube to use as motor mount perches in my YJ welded the driver side one 3/4" farther back than the passenger side. It was a bitch to get the engine in. Then to line up the transmission took and act of the lord. What is worse is that at the rear where the transmission crossmember is supposed to line up to bolt to the frame was kicked off 3" to the passenger side once I had the T-case and transmission bolted to the engine.

Meaning, I had to get ratchet straps and ratchet it into place to try to get it to line up.

Mewing8 05-16-2013 05:32 PM

Use M.O.R.E. motor mounts, can't screw up in placement.

indirocz28 05-16-2013 06:41 PM

^^ +1

CAJUN YJ 05-16-2013 09:38 PM

Dam sounds like that was a pain in the azz! Just glad to hear you was able to make it work. If def goin to take my time.
ESP with the little time I have to really work on it, between work an a little one on the way, it will be a little tuff but it's going to happen sooner than later.

I'm going to start pulling stuff out of my jeep this weekend. sand an paint most of the exposed frame after I get everything out of the way.
I found my adapter for my ax15 from Novak and my radiator with fan off of eBay.
Does anyone have any experience with them? Any good?

indirocz28 05-17-2013 09:36 AM

Novak is good stuff, and Depends which radiator & fan kit you bought. I may still have some saved in my watch list.

Here is the thread of headaches:

denisbaldwin 05-17-2013 11:03 AM

A lot of this is going to be preference. You can do as I'm doing and use the computer from the truck in your swap. I have aftermarket gauges anyway, so that works for me.

indirocz28 05-17-2013 11:05 AM

I agree with Denis. All personal Preference. On the other hand, let me do some checking with this TJ my buddy put a 5.3L LS series engine in. I'm pretty sure he is using the factory gauges.

denisbaldwin 05-17-2013 12:05 PM


Originally Posted by indirocz28 (Post 3765510)
I agree with Denis. All personal Preference. On the other hand, let me do some checking with this TJ my buddy put a 5.3L LS series engine in. I'm pretty sure he is using the factory gauges.

For that, you'll need a piggyback or similar adapter (like from HowellEFI) that will adapter your old computer to your new engine (either with or without the engine's computer).


CAJUN YJ 05-17-2013 02:51 PM

Sounds great. I'm not worried about the factory set up gauges cause dey didn't work when I changed them out. I have all after market so I know ill beable to use em.
Thx for all the tips an advice guys I really apreciate it!!!!

indirocz28 05-17-2013 04:12 PM

No problem! Keep us posted!

AZ WRANGLER 05-17-2013 04:52 PM

I did a 5.3L swap about a year ago. I have a write up in here about it.

I used Novak for almost everything. They are expensive but worth the money. Their expertise is priceless!

My motor was out of an 04 pickup. I had to use the gas pedal and control box because it is drive by wire. Not sure if your donor is same or uses a cable. Check it out and verify.

CAJUN YJ 05-17-2013 05:37 PM

I don't think it is, it's a 98 gmc z71. I'm goin to have to look into that a lil more but dont think it is....I Mite b wrong.

BCDonny 05-17-2013 05:50 PM

how much are you planning to do your self? do you weld? what is your skill set for this, I think it can get very expensive if you don't do it all yourself.

CAJUN YJ 05-17-2013 06:06 PM

Yes I do weld. I'm a machinist by trade. I've been programming Cnc lathes an mills for 14yrs. I hobby weld on projects at home a lil things at work.
I'm just a lil nervous about building a motor lol. I rebuild Atv motors for friends my self because we mud race. It's the same concept just on a way bigger scale than an Atv motor. Lol I think I can do it, but nervous lol.

indirocz28 05-17-2013 11:20 PM

I did automotive school some years back right out of high school.

There are no issues with rebuilding the engine, but where you need to spend your money is on the machining and balancing of the block and rotating assembly. From there you just pay attention to the assembly steps in the manual. Then, make sure (if you plan on doing upgrades like heads and cam, higher compression pistons, or things like that) that you spend your money on a good tuner and don't just go out and hot rod it or it will detonate and fall apart.

Your donor engine 1998 z71 was still a manual pedal/cable throttle assembly. Beware that the spider injectors of that style of vortec take I think 80-90psi of fuel pressure to operate correctly. Its been some years since I have played with that MPFI, but do your research on what fuel pump is needed, psi, and flow rates in GPH. Last thing you want is to starve the engine of fuel.

2xs 05-18-2013 12:12 AM

Whatever you do, do NOT get rid of the donor until your Jeep is running and driving with the 350 in it. You will always find out you need that ONE DOOHICKEY, but only after you had it hauled away....

indirocz28 05-18-2013 09:01 AM

^^ Good point!

CAJUN YJ 05-18-2013 10:33 AM

Dam! ^ nvr thought about that. Great tip! My luck that's what would prob happen. Get what I think I need out the haul off an realize I need somthn else an have to go junk yard diving to get it! Lol

indirocz28 05-18-2013 09:24 PM

Just a tip, if you're running stock axles, I highly recommend upgrading to full size. I had so much torque with the TBI 350 ,sm465 trans Dana 300 t case and 4:10 gears that I was roasting the rear 37" tires into 3rd gear... Be prepared to snap stock jeep stuff.

CAJUN YJ 05-18-2013 09:43 PM

My old tired 35 in the back is time is about up anyway. Ill either go with a super 35 kit, ford 8.8 or a 44. Depends on what I can find in the junk yards around here. I'm def goin with 3.73's or 4.10's. not sure bout that yet as I'm not wanting to go too big cuz my wife will be driving it also. If it would be just me driving I would def put 35" boggers an 4.56. But I def think boggers will b too much for her an cost me way more money!
My lead foot, boggers, an mud in here in south Louisiana = destruction lol

CAJUN YJ 05-18-2013 09:44 PM

Also, can anyone tell me what is the bare bones of what I need to keep under the good of my YJ?
I know the brake booster, but what else??

CAJUN YJ 05-18-2013 11:18 PM

Ok guys, one last question for now, sorry for all the questions. Just tryn to b sure about what I'm doing.
To pull motor from my yj, do I just put a jack r block up my tranny? R is there a trick to this?

CAJUN YJ 05-18-2013 11:42 PM

1 Attachment(s)
Attachment 250811

indirocz28 05-19-2013 03:48 AM

Okay, take your time,
Take out the bolt holding your wiring harness together at the firewall, in door all clips for it where you find them back to the trans and transfer case (but liable those, just in case. Most GM trucks used a 231 T case, so good chance the computer from the GM will hook right up, but just in case you need to use the jeep plugs, you have them labled.

About your tranny: yes you can put a jack or blocks under it, in bolt it from your engine block. Don't forget that you may have to pull your slave Cyl fork out off the throw out bearing before separating the engine and transmission. It shouldn't matter, but I've had some that for whatever reason like it out before removal.

You will keep your brake booster and master cylinder, and steering shaft.
Get your stock jeep exhaust out of the way. You may be able to keep stock power steering lines, so try to save those.

Disconnect your fuel lines as neatly as you can. And try to use the GM ones coming off the engine to where they go back to the fuel filter.

Once you get your engine out, or about out, post up any more pics of issues or questions you have.

Also, just saw this thread, lots of Q&A here:


CAJUN YJ 05-19-2013 10:42 AM

Thx! Very much apreciated. I'm just wakn up an bout to get bk to it. Ill put up more pix when I'm bout to pull the motor.

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