Is there any possible way to change rod bearings without removing the engine? My son's 4.6 sounds like it has thrown a bearing. He is in a emergency situation, on a road trip and away from anywhere where we could pull the engine. Can the pan be dropped and new bearings slipped in from below? The truck is a short wheel base 4X4, and I know there will be cross braces that must be removed. I have on one of my Ford small blocks changed the oil pump just by dropping the pan. Sure it was tight but it has held for over 8 years now.
Am I dreaming or can we get him through this and back home? Anybody ever gone through this and won?

 

So far every mod motor I have seen when the rod bearings start knocking its too late. The rods get trashed fast and so does the crank.

 

Your saying pull the engine and have a total bottom end rebuild? That's going to have to start out with a 700 dollar tow home! Ouch.

 

Yup, once a bearing goes south, it usually scores the crank and the rod. I would definately have it taken to a machine shop (the crank and suspected rod) and have them surfaced. If you just slap a new bearing in there, it will be toast within a few minutes...

 

In my experience connecting rods either pass or fail.

The bearing inserts have hard steel backings that usually protect rods. If a rod bearing "goes south" so far it "scores...the rod" I'd reject the rod. Rods are forged & heat treated for strength, the frictional heat from direct scoring would probably ruin a rod.

Bearing inserts come in undersizes to accomodate reground/resurfaced crank shafts. I've never heard of them sold w/oversized backing to fit a rod that's been scored & "surfaced" to a larger size.

It looks like the front axle on a 4X4 needs to be dropped in order to remove the oil pan. In an "emergency situation" installing a new set of rod bearings in the field might very well allow driving it out, w/o further damage.

The phrase "thrown a bearing" isn't much to go on. Many bad bearing knocks can be gently nursed along, at least temporairly, in an "emergency situation". Usually you hear 'thrown a rod' which can be terminal, even though many a vehicle has limped home banging away! A thrown rod can ruin the block & crank. When a bearing "goes south" completely & allows the rod to hammer on the crank, it can 'spin a bearing' which will either 'throw the rod' or seize the motor.

Thicker oil can quiet some knocks temporarily, a phenomenon exploited by thickeners like STP.

 

I think he means he spun a bearing not literally threw the "rod bearing throught the bottom" as he says. If the engine was shut off immediately after the bearing spun you might get lucky(depending on the condition of the rod and crank journal. You won't know unless you pull the pan. You'll have to pull them off one at a time to find the one that is spun. Hopefully it's only one.

 

I wasn't sure what MD "means...literally" by "thrown a bearing".

I don't know who you are trying to quote, but a "rod bearing" isn't likely to get "thrown" anywhere.

My point was that usually a bad rod bearing will knock for a while & might be nursed along in an "emergency situation". Ultimately the rod will break & may ruin the block and/or crank.

 

I'd find a buddy with a pickup and a car trailer and drag it home at however slow a pace is appropriate. Depending on distance I might limp home as far as I could get and not care about writing off the engine because once they start making serious noise I'd consider them either a core or just junk.

Nowadays the economics of replacement with a used engine make fixing most seriously worn engines not especially worthwhile.

 

Spun or not, if you have a rod knocking the rod is trash. The hammering action stretches the rod cap. If you just install new inserts it won't last.

 

Yes, "usually" is the key word. The crank and rods on my 460 were pretty well scored. The crank needed to be turned .010/.010 and the rods needed a good hone and slight trueing (out of round). I traded my crank for a Std./Std. one however.

The rods will be fine unless you are running into the 8k-and-up RPM ranges (where the stock rods wouldn't work anyways). A machine shop can get them back to new again.

 

You'll "usually" never find me denying there are exceptions to every general rule.

In MD's case "usually" is presumed to be normal 'running into the 5-6k-and-below RPM ranges'. Millions of "stock rods" have failed at lower RPM. I'd reject any rod that was "pretty well scored & out of round" unless it was an "emergency situation" where long term reliability was not an issue. If a rod is damaged by frictional heat I seriously doubt "A machine shop can get them back to new again."

What scored your "rods"? Can we presume totally worn out & spun bearings?

Sounds to me like after the critical layer of soft 'Babbitt' bearing metal went "south" & your "460" was kept running & it was the bearing insert's "hard steel backings" that protected your rods as much as they did.

Good used rods are cheap, often less than $10@. New aftermarket rods, billed as better than OEM, aren't very expensive, often less than $20@. Why take a chance on damaged rods that have been "well scored", bent "out of round" & subjected to excess heat, if its not an "emergency situation"?

Machinist's work to save "out of round" rods sounds expensive. Note that to save "out of round" rods, the contact surfaces between rod & cap must be ground down precisely, then the resulting hole must be bored to spec. Somehow "slight trueing" or having "them surfaced" doesn't do justice to this exacting work. IMO "a good hone" can not restore roundness or diameter.

 

Hmmm...guess I'll have to remind my buddy (Terry Walters) - owner of --> ( Terry Walters Precision Engines Services ) about using re-furbished rods on his drag cars

I'm all for a new set of rods...but I don't have that kind of money...

 

Hmmm...guess I'll have to remind my buddy (ATC Crazy) that MD didn't inquire about lavishing attention on a drag racing motor. Those specialty motors are not "usually" noted for their long term durability & are "usually" built using costly & exotic high tech components.

Crazy: "The rods will be fine unless you are running into the 8k-and-up RPM ranges (where the stock rods wouldn't work anyways)."

IMO the exceptions also do not prove the general rule. We were trying to addresss MD's "emergency situation".

 

I went and flat pulled him home with my 250 Diesel, and the truck is now resting in my garage.
I guess now I'll start reading up on pulling the engine. The engine does sound like a complete write off. It just hammers when it fires up. Could have spun a bearing sealing off the oil passage and therfore starved the wrist pin. Any how the engine is dead, and we will be looking for a transplant.

Has anyone found a good guide, step by step on engine removal? The truck is 4X4 with automatic and air conditioning

 

I type to slow. lol Glad to hear to got it home.


For emergency purposes, an unusual (extreme) option is to cut the rod allowing it to bolt back on and run on 7. Bolting the lower rod in maintains the oil system. I have done this on one vehicle in an emergency myself. Might not be the best route for you. Mainly cuz you must get the rod and piston out first. And it wont come out the bottom.

As for rolling in bearings, you will need to know if the bearing has excess play, or has actually turned(spun) in the rod. If spun it will not hold. (Bearing crush is lost) The new bearing will run only a few minutes. (turns in the rod and cuts off oil supply.
- If clearances are just excessively loose, It can hold up with a new one rolled in given the RPMs are kept low. Depending on how egged the crank is, RPM is a one time deal. REV it and it is gone. I would estimate to not exceed 2500 and cruise lower.