4.0L Rebuild Questions

Looking at rebuilding/stroking my 4.0 but I've got a couple of questions. I've done research and know what I need as far as parts go but as far as doing a COMPLETE rebuild on the engine, what machine shop work is required. I know what I need in terms or gaskets/seals/moving parts but don't know much about what machine work is required to do it right.

Bore the cylinders, deck the block, deck the head, have a valve job done while you're at it. Grind your crank if necessary. Have then hot bath and blast parts while you're at it; makes them clean and new and ready for paint. I painted my block and it makes wiping off grease much easier, i.e. if you're looking for a leak on down the road it'll be easier to find.

cool, doesn't sound too bad.....anything else?

How nuts do you want to get?

Take a sanding roll and clean off any "casting flash" you find on the block and head (mould parting lines, usually. Stress risers, heat risers, and oil collectors.)

"Break" the edges of the combustion chambers (heat riser again - you don't need to remove a lot of material, just round over the machined edge slightly.)

Put a slight chamfer on all critical screw holes (cylinder head, crankshaft main bearing cap) so the top thread doesn't try to "pull out" when you torque the screws and lift something.

Make sure the casting proper is clean (not "no grease" but "no flash/burrs/other problems") before you start reassembly.

Yeah, it can get kind of detailed. The devil is in the details, and that's why I enjoy engine work. It's a purely objective form of precision that can be measured by anyone with knowledge of the proper tools. Body work takes an artist - which I'm not. Engine work takes a technician - which I enjoy.

pretty nuts it's got 212000km on it now but the body is in great shape so I wanna rebuild/stroke and have it last pretty much until the end of time I'm pretty anal about doing things right the first time and not having to go back later so when I rebuild it, I want it to be as close to "zero-time" as possible if that makes sense.

xjguy98 said:

pretty nuts it's got 212000km on it now but the body is in great shape so I wanna rebuild/stroke and have it last pretty much until the end of time I'm pretty anal about doing things right the first time and not having to go back later so when I rebuild it, I want it to be as close to "zero-time" as possible if that makes sense.

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A "cleanup" bore job is usually +.010" - and you can usually find pistons and rings in that oversize (yes, you'll be replacing pistons and rings if you overbore. Think about that if you decide to do the job, because it adds to the cost.)

Find yourself a book on "Engine Blueprinting" or performance engine building - you could pick it up locally, I'm sure, several weeks faster than you could get my book from me. I'm not sure how pressed for time you are. And, I'm sure there are details that I'll need to add to my book anyhow (the problem with doing something for years is that you get to where you don't have to think about it anymore, and some stuff becomes automatic that should probably be explained.) The Devil is in the Details.

Plan on spending a lot of knuckle-and-elbow work if you want a detailed engine buildup. The Devil is in the Details.

Also, plan on having a good small hand light for inspection - the bright beam can point up surface flaws that you wouldn't else see, and the spot tends to focus your vision. I find the SureFire G2 to be excellent for this purpose - not only is it bright, but the Nitrolon polymer housing won't harm anything if you drop it. The Devil &c... (The G2 usually goes for about US$35, I don't know what current exchange rates are. I prefer it for a mechanic's light - their MIL-spec anodised aluminum housings can be used to saw through other aluminum lights... And, most aluminum lights can at least scuff iron, especially if they've been anodised.) If you can't get the SureFire, get some light with a polymer housing with a good beam - or (worst case,) aluminum with a clearcoat or (very worst) a clear anno (since clear is about the softest of the anno jobs.) Treat this point as important.

An engine buildup can be just as detailed as you want it to be - anything from a quick re-ring and re-bearing to a fully anal cleanup job and making a block with 300Kmiles on the clock look better than new! Feel free to bounce ideas around and pick up anything you might not already know around here, that's what we do. Even if you've been building engines for a while, I'm sure you'll pick up something you didn't know...

I can personally say the 5-90 has given me hundreds of helpful hints and how to's in the last few months. If he says that the way to do something (i.e. RMS in oil for 30 minutes rather than dish soap) then I'm gonna follow his instructions to the tee. And if I get in trouble down the road its easier to say "I did everything just like you said" rather then doing something some off the wall way which adds many variables to solving a problem.