Rebuild or swap out engine - opinions please!

OK, so I am evidently just a dumb-ass in love with a truck, and I want to re-animate the poor neglected thing...

My '96 4.0 2-door has been a paperweight for over a year, after a long series of errors trying to diagnose and fix a bad rough-run issue. (See here, and here)

I'm a mechanical novice, so I hadn't done what now seems obvious - pull off the valve cover. I found a loose pushrod (way loose). Had a mechanic neighbor look at it. He says collapsed/bad lifter and bent pushrod, and something about the part the pushrod slides in.

So its major engine work to fix it - and I want to get opinions on which way to go and what you know about costs (the labor mostly).

The options (?):
1. Have it rebuilt - new cam & lifters, and may as well do new valves while its out. May need bottom end work - new top makes too much compression??
2. Buy a remanufactured or rebuilt engine and have it put in.
3. Buy a junkyard engine and have that put in.

As I said - I'm seriously NOT an experienced mechanic - so I need input here...

TIA

Perhaps the pushrod is bent, or the lifter is collapsed. But the issues you talk about seem to be largely intermittent. Mechanical failures of this nature are not intermittent.

Nixt said:

OK, so I am evidently just a dumb-ass in love with a truck, and I want to re-animate the poor neglected thing...

My '96 4.0 2-door has been a paperweight for over a year, after a long series of errors trying to diagnose and fix a bad rough-run issue. (See here, and here)

I'm a mechanical novice, so I hadn't done what now seems obvious - pull off the valve cover. I found a loose pushrod (way loose). Had a mechanic neighbor look at it. He says collapsed/bad lifter and bent pushrod, and something about the part the pushrod slides in.

So its major engine work to fix it - and I want to get opinions on which way to go and what you know about costs (the labor mostly).

The options (?):
1. Have it rebuilt - new cam & lifters, and may as well do new valves while its out. May need bottom end work - new top makes too much compression??
2. Buy a remanufactured or rebuilt engine and have it put in.
3. Buy a junkyard engine and have that put in.

As I said - I'm seriously NOT an experienced mechanic - so I need input here...

TIA

Click to expand...

Bent pushrod is easy - if that's all it is, you just replace the pushrod from up top. Remove the rocker arm, install the new pushrod (smear a little grease or assembly lube on the end balls,) and reinstall the rocker arm. Torque the pivot screw to 21 pound-feet.

If the lifter has collapsed, you're in for removing the head (there's no other way to get to the lifters.) In this case, you'll want to just go ahead and change all twelve, and inspect the rest of the valvetrain while you're about it (since you'll have to tear it down anyhow.) Might also be a good time for a cam swap - but it's not necessary to put in a new cam with new lifters (New lifters can be put onto an old cam - but do not put a new cam in without new lifters!)

Even if you have to pull the head, it's the sort of thing you can finish in an afternoon if you have help to move the head (it's heavy.) When you torque the screws back down, tho, make sure to put paint marks on the screws after they're down! Also, check the screws before you remove them - if there are paint marks on the heads, get new screws before you start! The head screws used can only be torqued to full preload twice before they're considered "failed" - it's a modification of the "Torque To Yield" screws as used on Diesel engines and some imports.

If you're not sure, just get new screws - it's cheap insurance (a set of head screws runs, I think, $50-75 - but it's cheaper than a blown engine or having to drill out or burn out a screw that broke off...)

I find that Scotch-Brite discs (chucked into a drill motor) are nearly ideal for removing gasket detritus from deck surfaces and the mating surfaces for the manifolds. They do a thorough job, and the finish left is very nearly ideal for assisting gasket sealing.

And, if you do have to change lifters, search up my posts on servicing the manifold gaskets here as well. Advice borne of experience - little tips you won't find in the manuals that make the job so much easier (I also find it easier to remove the head and manifolds as a unit, service the gasket on the bench, and install them as a unit - but I'm a fairly large guy, and can wave the thing around assembled. If you're not sure - get help.)

Well "generally" a bent push rod means the valve cam into contact with the piston
That could mean the timing chain jumped or broke? So it could be a big deal
Now you stated early on you’re a Novice and if you don’t want to learn how to work on an engine or don’t have the time or tools then you can buy a used engine at a salvage yard that usually run 300.-to as much as 600. (In my area of Ohio)
You can get a reman they are over a grand and up.
If you do want to lean and build yourself you wont save any money if you have all the recommended machining done to get the very best results but you will have that satisfaction that you created a new engine

Now it could be it got bent in some other way …not likely but in that case the info posted by 5-90 covers that scenario quite well

How many miles on the engine?
If it's over 150K, I would opt for a total rebuild if it's anything more than just a bad lifter.

If you have never done it before, then buy a rebuilt engine or have yours rebuilt by a quality shop.

Bent pushrod could also mean a stuck or bent valve, causing failure in the hydraulic lifter and premature wear on the cam.

Being as you're a novice, crack open a few books about your Jeep and read. If you have no clue on how an engine works, get some books about how a 4-cycle engine works. Educate yourself about the various parts of your Jeep. It'll pay-off in the long run.

I think the best thing for you to do is buy a rebuilt engine and ask your neighbor if he'd like to help with installing it. Take it slow and ask a lot of questions.

Bent pushrod could also be simple fatigue failure of the material (it's rare, but it can happen.) If the valve tried to self-clearance on the piston, I'm fairly sure he would have noticed it... Likewise a sticking valve - due to the lost power involved (and I'm going to go out on a limb here, but he didn't say anything about losing power. Even someone with very limited mechanical experience can notice something like that.)

Thanks to all so far.

Doing this myself is not really an option right now, though. Not that I'm not into learning and trying new stuff with wrenches, but as the linked posts show: When I try new stuff I can F*** it up pretty good, and I have been a year now with no jeep. I need to just get her up and running, and use what little time off I get to *drive* it, not wrench it. So its pay to have it done, whichever option I take...

Again though folks -
Can anyone offer pros and cons of my different options and which they'd choose?
5-90, you are really knowledgeable, and your opinions on that would be appreciated.

Oh-

The linked posts may not tell of the timing chain replacement or the many-times-misindexed distributor housing. I may well have f-ed up with either of these 'repairs' and caused the bent pushrod and collapsed lifter creating a new worse issue unrelated to my original random misfire issue.

This is another reason why I'm sending it out to be done - I apparently cannot be trusted with wrenches.