My first engine “build”

mbalbritton

mbalbritton

#@$%!
Joined
Mar 22, 2005
Location
Greensboro, NC
So, I’m sure I’ll have lots of questions, so I thought I’d start a thread. I’ve been into engine and stripped them before, but never “built” one. I use built lightly. This will either turn into a 4.0 refresh or a 4.6 stroker. Or maybe just refresh and then stroke it down the road. We’ll see as we get into it.

What I’ve got: ‘87 YJ 4.2 with an Mc2100 backed by an A999/207 combo. This 258 has been fairly typical. It runs and won’t die. #5 piston slaps like great Friday night! Or whatever night nookie nights for you.

I picked up a ‘94 4.0 from @spraypaintman of unknown quantity to both of us. But all signs we could check looked good. I’m guessing that it came out of an XJ, but don’t really know as it wasn’t original to the YJ we pulled it from. If anyone has any tell tale info about Configuration or marking or something, let me know. @Blaze who posted the 4.0 thread and seems familiar with these.

I picked up all unmolested wiring and all accessories that were attached. I’d say I’m 95% complete with parts. I’m sure that will drop as I go along and realize I need something else. So far, a cooling fan and power steering lines.

Here’s the fun stuff, first PICTs:
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And tear down:
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First problem:
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So… what I know so far about this engine from tear down.

- valve cover gasket Was coated with blue RTV
- head is cleaner than the block
- dropped a borescope down all spark plug holes and everything looks good, even has nice crosshatching on walls. I’ll see if I can pull some PICTs.
- intake was misaligned on last install and there was clearly a leak and a broken alignment tab.
- all pushrods feel true and under proper tension.
- all valve train moves freely and properly when spin by hand.
- there was no bell housing or starter so I have not heard it fire, turn over, checked compression…
- ALL intake and manifold bolts were able to be loosened with about 5lbs or pressure.
- no accessories seemed to have been recently removed.
- all spark plugs were consistent with a very light coat of black.
-No real apparent Oil leaking. Might could use a new front and rear main seal…just because it’ll be easier now.

Soooooo. That’s where we’re at and here’s what I’m debating.

Clearly someone has been into the valve train. There’s good signs the head has been off, maybe even replaced. I found an 0630 casting on the head, which I understand to be ‘96 and newer. I’m not seeing any cracks from the topside on visual inspection.

I’m thinking I’m going to pull the head and inspect for signs of over heating. Note that I did find that apparently some squirrels stole the Thermostat and replaced it with acorns.

I’m also tempted to drop the pistons and check them for crack. Might as well at that point I figure.

Thoughts going forward at this point:
- keep it EMP proof and put the carb and intake from the 4.2 on it
- leave it as is and figure out the wiring
- stroke and carb it.
- stroke and inject it.

Oh, and I’ve stated it many times before. I freaking hate wiring and electrical. For some damn reason, I just can’t wrap my head around it. For that reason alone, I’m tempted to go carb and keep it simple.

So, until next weekend, that’s the start.

Anyone around Greensboro/HP have a tig welder that could help me with my intake?

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Fuel injected and stroked! There ain't gonna be no zombie apocalypse! Haha
 
If you want to get away from a 30 year old computer and questionably Chinese sensors (crank position) the sniper kit and hei dizzy is the simplest least hassle way to go. Engine masters did a carbed 4.0 and it made more power than the stock efi, they welded a carb spacer to the stock horseshoe intake for an adapter. But the carb will not save you much coin and will require more maintenance
 
Those intakes are prone to cracking. Id look into studing the exhaust and intake during your build. Id get an aftermarket intake - future proof it
 
So, today was pressure wash the outside and look to clean it up a little. Some dumbass forgot he had the plugs out so, that sealed the deal on the debate of pulling the head to inspect. 🙄

Soooo,
heads GIF


To my delight, things look REALLY GOOD.

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This engine has been gone through before. There is zero play in any piston, things are just really clean.

Next I want to open the bottom end.
 
Bottom end looks pretty damn good too. All cam lobes are present and accounted for. However there is an interesting wear pattern that is consistent on all.
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Those two dark humps. I’m guessing it has to to do wear pattern for spinning the lifter.

I pulled one rod cap just to see. Looks pretty good.
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And the rear main bearing.

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I’m thinking this engine is looking pretty good.
I’m going to reseal everything, give it a thorough cleaning and a couple of cans of exterior “rebuild” and drop it in.

It’s already going to be a significant improvement over the 258.

Sorry to disappoint anyone looking forward to a stroker. But I will pull the crank and rods from my 258 to save for a later date.

So, the rest of this thread will be mostly around all the little shit people don’t mention that you have to do because I don’t care what anyone says, it’s not a “pretty much direct swap”. 😁
 
ckruzer said:
That definitely got hot at some point in its life.

Imho, those are borderline trenches bro. Its already that disassembled - Id polish the crank and put in new bearings
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Are you talking about on the rod and main bearings? I know they are visually there, but you can't feel them. Not that it's hard or expensive to replace them, jut didn't think it was worth it.
 
mbalbritton said:
Are you talking about on the rod and main bearings? I know they are visually there, but you can't feel them. Not that it's hard or expensive to replace them, jut didn't think it was worth it.
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Generally speaking, if they are immeasurable its considered "okay" by the engineers to run them.
General consensus is: they get that way from being out of spec, and particulate finding its way in. Reusing them is reusing something evidencing it is out of spec
New bearing are not that expensive. And you should be able to get a shop to polish that crank for <$100. If not pop up to bristol one weekend.
If definitely looks like the engine has overheated before, shed some particulate, which wore on the bearings. Double check the oil pump to make sure it survived.
 
SON OF A…MUTHA FLETCHER…

So last night I pulled out each lifter, one at a time to inspect the bottom face and put them back. One at a time as to have no chance of mixing them up.

Then tonight I wanted to measure the rod journals to see if they were standard or undersized. Not even thinking about it, I spun the block over and hear 9 of the lifters fall out and scatter across the floor or fall into the oil drip pan under the engine stand.

FAAAAAAAWK!!!!
 
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