SBC main bearing?

rod · 04-28-2024, 07:08 PM

some observations. there is crosshatch, albeit very light. looking at the cap bearing I find most of what I thought was bad wear...,appears to be a lite polish on one quarter. [crank looks real good. but possibly the caps are not squared up.] a few scotch brite passes, and the bearing looks real good. except...the center where the oil hole travels. the oil holes received just a very lite edge break with a rotary stone. it almost looks like that area got work hardened [factory steel 327 crank] and the micro polish wouldnt cut it down. #s 2 n 3 main and several rod bearing all exhibit the same look. is that possible?
thought n comments appreciated.
thanks Rod in AZ

Adger Smith · 04-28-2024, 10:01 PM

Rod,
Those cranks are not near as hard as most after market. A good grit cloth shoud cut it then go back with the fine micro polish grit. Too much stock removal can get an out of round or tapered shaft. Be careful.. Might let a good crank guy that knows his stuff do it. What you are seeing in the middle bearings may be crank flex or whip. How you come out of the burnout can whip the crank and if you are "Hard" on the 2 step..
There is a reason GM went to the larger rod and main journals.
Don't be afraid of more clearance than "They Say" you should run.
A lot of factors at play with issues like you are having.
Keep digging you will figure it out.

04-28-2024, 07:08 PM	#1
rod Member Join Date: Dec 2009 Location: Kingman, NW AZ. in the middle of the longest stretch of Route 66 Posts: 315 Likes: 0 Liked 20 Times in 15 Posts	Re: SBC main bearing? some observations. there is crosshatch, albeit very light. looking at the cap bearing I find most of what I thought was bad wear...,appears to be a lite polish on one quarter. [crank looks real good. but possibly the caps are not squared up.] a few scotch brite passes, and the bearing looks real good. except...the center where the oil hole travels. the oil holes received just a very lite edge break with a rotary stone. it almost looks like that area got work hardened [factory steel 327 crank] and the micro polish wouldnt cut it down. #s 2 n 3 main and several rod bearing all exhibit the same look. is that possible? thought n comments appreciated. thanks Rod in AZ

04-28-2024, 10:01 PM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: SBC main bearing? Rod, Those cranks are not near as hard as most after market. A good grit cloth shoud cut it then go back with the fine micro polish grit. Too much stock removal can get an out of round or tapered shaft. Be careful.. Might let a good crank guy that knows his stuff do it. What you are seeing in the middle bearings may be crank flex or whip. How you come out of the burnout can whip the crank and if you are "Hard" on the 2 step.. There is a reason GM went to the larger rod and main journals. Don't be afraid of more clearance than "They Say" you should run. A lot of factors at play with issues like you are having. Keep digging you will figure it out. __________________ Adger Smith (Former SS)