Changing rod bearings in the car?

[RawGN]

Just did a cam change and 100 miles later, the engine has developed a rod knock. 20k on engine, havent had any knock issues (detonation) so my only guess is crap from camshaft break-in took out a bearing. Knock isnt that bad yet and I havent driven the car since so Im hoping the crankshaft is ok.

My question is, who has changed out rod bearings without pulling the engine from the car and how successful was it? I know it would be better to pull the engine out but I live in an apartment and dont have the luxury of a shop to do so.

Thanks in advance.

 

[azbob]

If you do change the rod bearings, the life expectancy with the new bearings will be short due to the contamination throughout the oiling system. Need to pull the engine, disassemble, flush and verify what caused such an early failure.

 

[RawGN]

If you do change the rod bearings, the life expectancy with the new bearings will be short due to the contamination throughout the oiling system. Need to pull the engine, disassemble, flush and verify what caused such an early failure.

I totally agree, but as mentioned, I dont have the luxury of a shop or garage to pull the engine. I want to know if anyone has had any success simply hand polishing the rod journals and replacing the bearings while the engine was in the car.

 

[azbob]

Previous threads on the same topic indicated a very short duration to another failure. You can search and find who said what. It is just futile to try and do what you asked and not end up having more of the same trouble.

 

[novaderrik]

i know it sounds insane, but i know of people that have replaced the crankshaft with the engine in the car. i'd imagine that the trans would have to be slid back to get the flex plate bolts out.

 

[Dabigguy]

Like they said, the contamination will still be in the heads, intake valley, turbo, valve covers, front cover......plus, if the crank is scored then you've got to pull the crank. Sure you could polish it a little while still in the car, but the polishing will introduce metal from the crank and grit from your polishing media into yout engine. This is assuming that the wind doesn't kick up dust while you are laying on your back for hours saying dirty words.

Do it if you wish, but try not to be disappointed if it only lasts a very short while.

 

[KevinB]

If you have a rod knock, chances are that rod is beat up and will need to be resized. Trust me, been there done that. Years ago I tried. It ran good......for 10 minutes. Everyone told me it could not be done. thought I'd try anyways. Save yourself the time and money.

 

[HotAirGN]

I have done this before with a N/A 3.8. It was real easy. Take the cross over pipe out and then pull the motor mount bolts out and then jack up the harmonic balancer and there is plenty of space to drop the pan.

Take out the bearings, wipe the crank, plasti-gauge, then put them back in. While your there just take the caps off everything and check for copper wear. But then again thinking about it I did spin the bearings again about 1 year later. Did the same thing once more (this time had to get a .010 bearing) and sold the car (back in my HS days)

 

[TurboDave]

Don't do it!! As mentioned, if there's rod knock, it's for sure out of round. And there's trash throughout the engine.

 

[Red Regal T]

With all due consideration to the advice already given, it's a pretty straightforward job. You should be able to do it in 4 or 5 hours. I don't see any reason to plastigauge it. Either it's going to hold, or it isn't. How many miles in on the motor? What caused you to change the cam?

 

[ijames]

With all due consideration to the advice already given, it's a pretty straightforward job. You should be able to do it in 4 or 5 hours. I don't see any reason to plastigauge it. Either it's going to hold, or it isn't. How many miles in on the motor? What caused you to change the cam?

Like John says, it is pretty straightforward and it all comes down to how long you need it to last. If you did the cam because of a wiped lobe, the bearing failure is most likely the result of the metal that went everywhere as the lobe wiped, so you already have lots of metal in the lifters, rockers, guides, rings, cam bearings, etc. That means you really aren't risking much more damage because it's mostly already happend . Doing the rod and main bearings will last a while but eventually the oil pressure is going to go south as the cam bearings (and rod and mains) fail. My ouija board says you might get 5000 miles before the next knock (+/- 5000 miles).

So, how long do you need to keep it running in limp mode and is it worth it to spend money now on bearings knowing you will be needing to rebuild the motor in the not too distant future no matter what?

 

[GNTIM]

My alky stopped working several years ago and I noticed a knock at start up there after. Pulled the bearings and 1 was down to copper. Replaced them all and was very meticulous and clean about the operation, but it still runs today. If the crank is damaged, all bets are off, mine was fine.