Bugout4x4

There are probably 6 generations or more of those who have replaced bearings with new on an old crankshaft. Depends on the shape of the crank. If it's clean smooth and not scored bad, the tolerances mic out to be within specs of what the new bearing size is, and the journal is not hammered flat on the push side, why not? I lost count years ago of how many I have done it to with never a problem.

Bugout4x4

May I suggest checking the rest before ordering anything at all? While you have it apart? Personally I have never changed out just one bearing and would discourage it, always in full sets, and always all bearings while I'm there rods, mains, new oil pump depending on how many miles it has on it and a new rear main seal.

Just one tow later on is going to be a lot lot more than the cost of these few parts to do it the right way now.

sambroom

Really bad news. The rear thrust face on the crank is hashed bad:


So now what? I paid $1200 for this engine in "new condition," It took me months to get it in, a little here and there in the bits of time I could spare... Now do I have to pull the whole darn engine again AND rebuild it?

This is getting to be way too much for me.

sambroom

New day. I'm feeling a bit more optimistic. I feel like pulling the engine this second time will go way smoother, because I'm past the learning curve. I also pulled the crank out of the old motor, and it looks great. I can't see any issues that would even warrant machining, but I called a machine shop to see if I could bring it in and have it evaluated as a potential drop in. He said sure, but he scared me a bit by telling me I should rebuild the whole motor now because the shot bearing will have contaminated the whole motor with tiny metal shavings, and will wear everything out in a hurry. Is this a concern? If I just change the oil a few times over the first 1k miles I drive it, is it possible to flush most of the contamination out?

dave1123

Jeeps have this fixation with magnets. There's one in differentials (at least my WJ), one in the transfer case, and one in the transmission. Why not one in the oil pan? A couple of neodymium ring magnets in the oil pan should take care of any metal shavings and change the oil filter a couple of times in the beginning to catch the aluminum and lead.

sambroom

Ooh good idea on the magnets!

So I have the crank out on the old engine, and it seemed pretty easy... Its heavy, but not unmanageable. I took it to the machine shop to get polished. Meanwhile I'm considering going ahead and pulling the bad crank out of my jeep with the engine still installed. Seems like all I'd have to do is pull back the tranny (done it twice now, so I'm pretty confident at it), pull the water pump pulley so I can get at the crank cover, and its out. Im thinking I can keep the engine cleaner too because dirt doesn't fall up. Anything else I might run into doing it this way?

Two questions:

With the crank all the way out, the upper bearings would be pretty easy to install, except that I am considering doing it upside down. So is it ok to use a dab of grease or something to hold the bearings in place while I put the crank in under them?

What products would you use during assembly to assure a smooth first start?

On crank position relative to the cam during install, the sprockets on the cam and crank are slotted so they can only fit in a single position, so would it be enough to use paint marks on the chain and sprockets to ensure the right install position of the crank? Otherwise, how do I ensure correct timing when I install the crank?

dave1123

You might want to use a small jack, like a screw jack, when installing it and put covers on the rod bolts so you don't scratch it. Put the #1 and #7 main caps in loosely to hold it in place. Vasoline works to hold the bearing shells in place because it melts into the oil after startup. Just the spring of the shells might be enough. Mark the rod and main caps as you take them off so as to not switch them around. The bearing bores are machined in assembly when they are made.

Install the timing chain so that the 2 shafts and the timing marks make a straight line, as in camshaft, cam gear mark, crank gear mark, and crankshaft in that order. If you haven't pulled out the oil pump drive gear, your ignition timing should still be okay.

The manifolds are the hardest part of this engine. I've even heard of guys pulling them together with the head! That seems awkward to me because just that head weighs 78 lbs! If you have a cherrypicker, or overhead chainfall, maybe.

ONE THING!! When you put in the front headbolt on the driver's side, use thread sealer on it. It's the only one that's threaded into the water jacket and will eventually leak coolant. The coolant wicks up thru the headbolt threads into the first manifold stud, then into the exhaust. The only way to find that leak is from deposits on the manifold nut. NOT locktite, use thread sealer (Locktite 592 sealant). That headbolt also uses a lower torque that the others because it's not supported as well. 100 instead of 110. They say you can use headbolts twice, but I prefer to replace them every time.

sambroom

Yeah the manifolds are a pain. Maybe an ignorant question, but you seem to be suggesting that I will need to pull the head and or the manifolds to put the crank in... Why would that be? if I don't pull the cam, the valvetrain would remain unaffected right? I'm not planning to pull the distributor either...

dave1123

Sorry, I got you mixed up with a guy I'm posting with that's planning a valve job and head resurface. Just ignore my rambling! My wife always did anyhow LOL!

I'd just use regular engine oil for assembly. Pull the ASD relay and crank it until the oil pressure needle jumps, then install the relay and fire it up. Let it idle until it's warm, then drive it normally.

Bugout4x4

Glad to see you are more optimistic! It's your call, but keep in mind that all that linear shaft movement may have also caused some abnormal wear in the rest of the moving parts in there like the wrist pins or cylinder walls. Just something to consider in all this.

sambroom

I understand. The good news is that I checked the compression numbers before I bought the mill. They are all good. Hopefully this runs ok for me for some time.

The crank is done, and the machine shop supplied a bearing set. I'm in the process of pulling the transmission back so I can get the old crank out and the new one in (Again, I'm going to attempt this without pulling the engine).

Any other tips?

Bugout4x4

Can you get to the crank/flexplate bolts? Rod bearings too right? Rod bearings need to match the size of the crank of course. And a new rear main seal would be real important. You don't want to do all this again JUST for a seal!

sambroom

I do have a new rear main seal, front main seal and new oil pan gasket. I dont have a crankcase cover gasket though... I was thinking of just doing an RTV bead... Good idea, or no?

Bugout4x4

By crankcase cover which cover are you talking about exactly? The oil pan covers the crankcase right? and you have that gasket right? Are you talking about the timing chain cover?

Once again... both new main AND rod bearings to match the rebuilt crank right? lol Sorry...but this is pretty important!

Bugout4x4

Since it looks like you are in a hurry and might try to do all this tonight. These all have to be properly torqued with a torque wrench. You have one right?