Changing rod bearings with engine installed

[iTurbo]

My Shelby Lancer has been down for quite a while and I'm tired of not being able to drive it. It still runs and drives but has a bottom end noise which I'm pretty sure is a failing rod bearing. That is the only thing wrong with the car though, so I'm thinking of putting it on jack stands and removing the oil pan in order to install a new set of rod bearings.

The engine doesn't 'knock' yet, although it does make a taping sound that lasts for about 1/2 second upon startup. It also makes some noise while driving, but that pretty much disappears when I give the engine some load. The noise is present mostly at light load and cruising but is quiet on decel and under load.

Is simply changing the rod bearings with the engine in the car a bad idea in lieu of a full rebuild? How will I know if the crank is too damaged to bother just replacing bearings? The engine has about 120k miles and has never been rebuilt, although I did replace every gasket and seal and the oil pump a few years ago. I have a set of standard size and .001 oversize rod bearings. Which ones should I use if I do this?

[Aries_Turbo]

youre going to have to get in there and check the condition of the rod journals and the size of the rod journals before deciding on what bearing to use or whether to leave the engine in there.

if the rod bearings are whooped, the mains may be also. might wanna check them too but they are harder to measure with tools but plastigauge may work.

Brian

[iTurbo]

Ok thanks for the info. Looks like I'll at least take the rod caps off and have a look before removing the engine. If the journals still look OK without obvious damage, can I use a digital caliper to measure them? Or would I just use Plastigauge to check oil clearance?

What kind of noise would indicate main bearing problem?

[Aries_Turbo]

you should probably use a micrometer rather than a caliper. more precise measuring tool. plastigauge would work too unless the surfaces are chewed up.

as for main bearing noise, cant say i know what that sounds like. only rod knock noise.

Brian

[thedon809]

I don't know that main bearings could cause a noise really. The mains just spin. No up and down motion like a rod journal. Excessive end play from worn thrust bearing might be able to cause a noise. More likely blown out rear main seal.

[iTurbo]

I got the old rod bearings out today and my hopes of simply installing new bearings were quickly dashed. They looked horrible! All of them were crap, although remarkably the crankshaft looks pretty good to me. I'm amazed I wasn't hearing more noise. Suffice to say the engine is getting pulled and replaced altogether with another TII that I already have all the machine work done on.

I don't think the bearings were original since I couldn't find a date stamp on them. There were some numbers stamped in the back side of the shells, but they were "C 11" or "C9" and all had "1-7" on them as well. All of the bearings had the vast majority of the wear in the upper (rod side) of the shell. They had large chunks of bearing material missing, and most were cracked at the upper most section of the shell. #3 was the worst and the upper shell came out in two pieces and was just hammered all over with most of the surface gone. #2 upper shell fell apart I two pieces just wiping the oil off.

Strangely, the bearings didn't have any copper in them. They appeared to be aluminum. The cap side of the shells were so loose fitting inside of the caps they wouldn't even stay in and the bearing tang didn't appear to even be right for the rod.

[zin]

Sounds like they a. might not have been the right bearing, and b. got a bit hammered from detonation, or c. a combination of both!

Was the oil pressure low? Once they start to go, the windage tends to go up quite a bit and so oil pressure can suffer (and be an indicator of bad bearings...).

Mike

PS Main bearings tend to make noise on start-up (no oil to cushion things), and will have a deep sound from the bottom of the engine that tends to go away (mostly) once the oil pressure comes up.

[Lotashelbys]

The easiest way to tell that main bearings are wore before you tear into it is to watch oil pressure right as you tip into the throttle and if the pressure goes down a few pounds before it goes up then its time to change the mains. I have done a few motors now that made no audiable noise but lost oil pressure at throttle tip in.....

[Tbird232ci]

The easiest way to tell that main bearings are wore before you tear into it is to watch oil pressure right as you tip into the throttle and if the pressure goes down a few pounds before it goes up then its time to change the mains. I have done a few motors now that made no audiable noise but lost oil pressure at throttle tip in.....

That's not what I like hearing...

[trannybuster]

Thats all mains, I had a 2.5 that made horrible noise, I drove it all winter long and when I took it apart I couldnt believe it even ran with that much main bearing clearance, it was horrible, the worse Id ever seen. Made noise with light throttle(crusing) and startup.