Bad main bearing symptoms

[65shlbycln]

In the past few days, my 289 has started to run rough. When going through the revs, it almost sounds like a flat-4 out of a subaru.

I was told that my main bearings should be changed pretty soon.

Could this be what is causing the engine to run rough?

 

[ozstang65]

How's your oil pressure? Bad mains will leak a lot and reduce pressure, a spun bearing, although I've never actually heard one, is an apparently very obvious noise.

An off-tune sound might be it not running on 8 cyls

 

[69Rcode_Mach1]

Did your mechanic check your bearing clearances when you put the engine together?

 

[brianj5600]

I had a turbo Buick that spun a main. It knocked under heavy load, not really any noise if just cruising. I guess the crank was supported by the next bearing except uder load it flex enough to knock. I babied it around for weeks until a rod fed by that main went south too. If it seems like a miss, it aint the bearing. If it souds like a jack hammer inside it is a bearing.

 

[Great68]

Did your mechanic check your bearing clearances when you put the engine together?

I think his bottom end is still stock.