Rebuild or Replace?

[Boogalooper]

So, I just started training to become an Automotive Maintenance Technician this week :wings: and soon (monday) we will be able to get our vehicles in the shop and start digging in.

So, my question is, should I take the tired old 4.0 which has an oil leak some where. It was ran out of oil at least once that I know of, and who knows when the last tune up was. And rebuild it, I would end up going through it with a fine tooth comb, seeing as we have 4 months in the shop this semester and we're focusing on engines.

Or, should I go with option 2. Which would be get a newer 4.0 (so in the future I can chip/tune it) and rebuild that before dropping it in.

Honestly either way I'm going to rebuild the 4.0 out of the 90 XJ, because I have a line on a '86 MJ for around $500 I've been thinking about buying, and if I do buy that I'll drop the 4.0 in there eventually.

Just seeing what you folks would do if you were in my position. I really want to have it running/driving well by the winter months, which really take off around December which is the end of this semester anyway.

 

[bob91yj]

Build a stroker engine if you're going to rebuild.

 

[JPK]

Build a stroker engine if you're going to rebuild.

X2

Whatever 4.0 your going to rebuild it would be cake to go stroker while you're at it.

 

[acasper708]

My buddy just finished a rebuild stroker kit on his jeep. It was pretty easy and he used his old block.

 

[Boogalooper]

I do plan on going with a stroker, honestly I have no idea what that is, but I will look into it more.

I also plan on doing some performance mods in the future (we have a full semester on engine performance coming up) so at some point it will be all done.

Edit

So I looked it up, and I understand what it is now, pretty similar to what I was going to do any way, just now has a name to it.

Can anyone recommend any good kits, or have any info on what to watch out for? Or something you wish you may have done and didn't on a rebuild?

 

[JPK]

A pita that I have run into -
So, you rebuild the top end and the bottom end - a complete, careful and thourough rebuild, the engine is good for another 150 0r 200k miles - but now your water pump leaks, or your distributor wobbles, or....

So, address all of the potential issues with bolt on pieces and parts. Nothing is more frustrating to me than knowing your engine is good to go and go strong, but you can't go because of nit picking secondary but important accessories.

Also, there is no such thing as a too clean block, head, spring, pushrod, piston, etc, etc, etc to begin with after disassembly.

There are some articles on buildong a stroker - or a bored stroker - an the internet, a search will help. I don't know of any kits though. Golen Engines may be a source for info or some parts, they rebuild 4.0's to 4.6l stroker specs. To get all of the benefits of a stroker, you will need to do the intake side too, including injectors, etc. Which, if you need to replace anyway, is not too bad, I think.

JPK

 

[Bodo]

No kits, just piece it together with off the shelf parts. www.jeepstrokers.com has tons of real useful information.

 

[Boogalooper]

Thanks for the helpful replies and the link too! With in the next week or so I hope to start pulling the engine and start cleaning it. (If my instructor lets us start early, we're not supposed to be doing engine work for another 2 weeks, until then it's just PM's like oil changing and stuff)

when I do start the build I think I'll start a thread and be sure to post lots and lots of pictures.

I'm also going to need to do 2 strokers or, at the very least rebuild the second Jeep I just bought (91 Cherokee Laredo for $300 (runs and drives))

 

[Hill Bill E.]

Use quality parts. It's been my (hard learned) experience that saving a few bucks today, ends up costing a whole lot more in the long run.

The last thing you want to do, is rebuild that motor twice.

:coffeedrink:

ETA: Welcome to ExPo!! I'm about 2 hours due north of you.

 

[Bodo]

I built a 4.6L stroker about a year ago. If you have any questions, I'd be happy to answer them if I can.

 

[TMPhoto]

As a technician myself I say go for the rebuild. No reason to put a new motor in if the block you have is fine. Just check the block for warpage, chances are if they ran it without oil they may have disregarded the temp going up as well. Also check the crank and im assuming youre going to replace all gaskets/seals and rod bearings at the very least?

Good luck, wish my boss would let me use the shop for anything other than quickie things

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[Boogalooper]

Well it's not my boss, it's my instructor, as I'm in school and the instructor wants us to work on our own stuff. Chances are if we are working on our own stuff we will actually finish it.

So, on craigslist I found a 4.7 out of a grand cherokee for $400 or a new 4.0 out of a 95 XJ for $300. I would like the bigger engine of course but I'm not sure what would be involved with the swap. I would also like the 4.0 from the 95 because of the new computer, but I'm not sure what would be involved with a computer swap, any one with more experience then someone who's been in school for a week care to shed some light?

 

[bldeagle10]

do a stroker and post lots of pix! I'm thinking about the same and it would be sweet to have a stroker build thread on here that I can reference to

 

[JPK]

Let the KISS Priciple guide you here.

You have enough on your plate with a rebuild, especially if you are going to stroke the 4.0. You may find transmission issues as well... Leave the computers and different engine configurations alone until you have at least one good, solid rig.

Swapping engines = welding or at least bolting in new engine mounts, new transmission or adapters, new trans mounts, new drive shafts, transfer case adapter potential, cooling system questions, fuel supply questions, .............

BTW, in case you didn't know, the 4.7 from the GC is a V8 and not a factory stroked 4.0 straight six.

JPK

 

[TMPhoto]

Im new to Jeeps so Im no help in specifics but when it comes to computers, usually you want to keep the computer that came with the motor.
Sounds like you're coming into a huge project with relatively no experience. If I were you i'd build it stock, with reliability and longevity in mind. What people dont realize is you change one little thibg on the motor it changes EVERYTHING....usually reliabilty and/or daily drivability goes out the window. Not to mention emissions regulations, mpg, drivetrain and transmission stress, etc.
Now you can still do a stroker or build of your choice with these principles in mind, but you're going to need the knowledge and experience to help.
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