The bearings will only wear down quickly if the crank journal is damaged as well, and the crank journal damage is dependant on how much the existing bearings have worn / amount of contaminants that have run through the engine. The bearing material is softer than the crank and has a couple thousanth's clearance to maintain a thin film of oil between the bearing / crank. When a bearing "spins" it means that the oil film had been broke, allowing the crank to "grab" the bearing surface and "spin" it in the rod. At this point both the rod end AND the crank need to be resized, and oversized bearings need to be fit.

*IF* the bearing isn't damaged beyond normal wear, and *IF* the crank journal has NO marks in it, you can get away with just putting in a bearing, however the smart way to do it is to pull the crank and have it surfaced, and then replace all the bearings with oversized ones. Remember, the junk that comes off the worn bearings passes through the rest of the engine and is probably embedded in the other bearing surfaces as well. If the rod is truly the problem and is slapping that hard, I doubt that any oil additives / different viscosity will keep it from further damage.

Bob

 

+1 Bob

 

Well, I installed my CAI today and noticed my plenum is for sure blown. Quite a bit of oil in there. Could the burning of the oil be causing this knock, maybe something like a spark knock or similar?

 

Can't oil blow back into the plenum if there's a pcv problem? (clogged valve / line) Still hard to mistake that for a rod knock though.

Bob

 

So I have been evaluating my options here. First I need to pull the pan and check the bearings and the crank, but I assume I have 3 options:

1) Pull current motor, repair any damage (replace/resurface crank, replace bearings, etc), replace any gaskets that need to be replaced (Plenum) and put back in. Most unfavorable because this is my DD and I have no other vehicles I could use unless I bum my parents for a ride everyday to/from work.

2) Buy a used motor, change any gaskets that need changing, check bearings, etc. Pull my motor and replace. Most expensive solution, but quickest and easiest. Car will only be out of commission for a weekend. Then try to sell old motor for a core or scrap.

3) Drive it till it dies, then be out of a car for a while until I can think of what I'm going to do.

I wish I had the skill to pull the pan and pull the bearings and possibly replace them myself, but I cant because a) don't have the proper tools, and b) nowhere to work on it (live in a condo. public parking lots.) My dad hates working on my cars because how many problems I have, so that's why he objects to pulling the pan. (I have always gotten cheaper, high mileage cars because that's all I can afford. Trans was rebuilt, so motor will be too. I have put way too much money into it already, and I'd take a HUGE loss selling it now.)

I'm sure a shop would charge up the *** to change out bearings, and not to mention the BS lies they'll make that I need to replace much more than I really need to so they can make some more money. That's why I hate taking my cars to shops.

 

1.If you go thru the trouble of pulling the motor, taking the crank out etc I would go ahead and redo the entire engine. You are just about there anyway at that point.

2. A junkyard engine has its risks. These guys have a pretty good rep for quality and price for a crate engine: http://www.cmengines.com/se/search.aspx

3.If it is your bearings and you keep driving it, you will eventually spin the bearings and then you got real problems. I would at least take it to a good shop and have them confirm it is the bearings.

 

You need to diagnose the problem fully first before making any decisions. I think it was mentioned earlier, but a rod knock can be isolated by pulling the plug wires one at a time while running. When you hit the one with the bad bearing the noise should pretty much stop, ignoring the obvious miss that you'll have with the non-firing cylinder.

Dropping the pan is no easy task on a D. You have the choice of lifting the engine or pulling the front housing to gain access to everything, otherwise it's not coming off. Also, while rebuilding an engine is really not that hard to do, it's vitally important that ALL the problems are found and corrected, otherwise you're just wasting time & money. IMHO, pulling the pan to replace one bearing isn't really an option. If the bearing is gone the metal has made it's way through the rest of them as well, and they're not far behind. It snowballs from there.... rings, cylinder wear, valvetrain work, timing chain, etc.

Junkyard motors are a crapshoot at best. If you can find one that you can start & run before you buy it, it looks clean, and the oil looks good in it you have a better chance of it lasting, but it'll probably cost you a good buck. Buying a rebuilt short or a long block is probably your most cost effective option, but it's also going to mean that someone has to pull the old motor, transfer over parts, and re-install. Again, not terribly difficult, but very labor intensive and expensive if you pay someone to do it.

Bottom line, troubleshoot first, price out your options, and then figure out if it makes economical sense to put more $$$ into the vehicle.

BTW, I don't consider driving the vehicle as it is now until it dies an option.... if the bearing is gone it's only a matter of time before it lets go completely. Where are you going to be when it happens? Doing 70mph on the Interstate?

Bob

 

Unfortunately, I'm taking this risk everyday. It's my DD. I'm 18 years old with a full time job. Not much I can do at this point. I don't have another car to use, public transportation would never work for me, and I can't afford to buy another car to drive while I fix the D.

I found a shop on craigslist selling rebuilt 4.7s. I called and asked if they do 5.2s and they said they can. I might take it to them for a diagnosis and if the cost isn't too bad and the time isn't TOO long, I might do it.

 

Sorry, I re-read my post and realized that it comes across as a bit arrogant. Not intended that way at all! I completely understand that you're strapped for cash right now, and I appreciate the fact that your 18 with a full time job. (Way to go BTW!!!) but driving it with a bad rod knock is playing with fire. It's going to drop, and when it does you stand a good chance of breaking other things in the process, costing even more money.

Also, I would think that a 5.2 should be significantly cheaper (and easier to find) than a 4.7 is. It's been around for a long time.....

Good luck!

Bob

 

It's cool man.

Will pretty much any 318 fit, such as one from a 1991 Ramcharger? It's just a DD. I don't need much performance stuff or anything, so a used motor that runs good with a tune up (gaskets, seals, adjust valves, etc.) and I should be set. I will, though, be using it for some light towing (small 18 ft. camper) and some light offroading.

The money situation is fairly tight. I just paid $1898 for a heavy duty transmission rebuild (for towing). Then all of a sudden my motor started knocking shortly after, so this was unplanned. I still owe about $1200 on the rebuild loan. I make about $360/wk, and a minimum $110/mn. loan payment. Including gas and food costs, I don't have much to spare. So a ~ $400 used engine + some extra for a tune up is ideal vs. a $2500 rebuild.