Knocking L98

[gvette85]

My daily driver is an 85 Corvette.It has 100,000+ miles on the motor.(some pretty hard ones too I might add)Anyway I went out to crank it and the battery was real weak,would hardly turn over.Hooked up the charger and after about 15 min.I tried again.The motor spun over and almost caught but then kinda backfired through the plenum. I stopped and went and bought a battery.Put it in and it fired right up,only now its knocking.Damn.Shut it off and ran a compression check.Everything seems ok ,has compression on all cylinders(no bent valve).Pulled the valve covers and checked the push rods,all ok so no collapsed lifter.Getting bad vibes by now.Jacked it up and pulled the dust cover off and checked the converter/flex plate bolts-all tight.Crap,really getting that sinking feeling now.Put a long screwdriver against the block and listened while the motor idled.Noise is definately low in the motor.So now I'm pretty sure its spinning a rod bearing.Any other suggestions before I pull the motor out?Any input will be greatly appreciated. Glenn

[Matt167]

ground plugs 1 at a time, if knocking stops, that rod is going to spin the bearing, if it hasn't arleady.

[gvette85]

Thanks for the tip Matt I'll try that

[Dave Severson]

Just pull it out now and take it apart before you do anymore damage..... Doesn't really matter which bearing spun, no reason mess up the crank worse then it allready could be.....

[Matt167]

yep, I'd go for that advice myself.

[gvette85]

yeah you're right ,if its a bearing its gotta come out,just thought some of you guys might know something I overlooked.I'm gonna pull it and tear it down.I appreciate the input,Thanks,Glenn

[thesals]

just put some 20-50 in there so you cant hear the rod knock.... if you cant hear it, it must be ok right?