Scratched Main bearing from Clearance measurement - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 09-15-2019, 11:21 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
Scratched Main bearing from Clearance measurement

Just to let you know I have another Thread about the engine I'm building, and I decided to make another thread because I have a question that is not about the components of the build but a question about something particular.

My block is a 350 sbc gen 1. Its a clean bare block at the moment. I installed the new main bearings and torqued the main caps. I was measuring the clearance with a dial indicator and afterwards I noticed there were some scratches on the bearing from the dial indicator.

The bearings have a thin coating of some sort of metal. So the scratches are shinny compared to the parts that are not scratched because under the first layer it looks like another metal. I did not put any oil on the bearings before I measured the clearance.

Should I replace the bearings and put oil on it next time I measure the clearance or do you think Im okay? Is that small layer of metal going to come off anyways when the crank breaks in?
Thanks

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-15-2019, 11:26 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
I meant to say dail bore gauge.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-16-2019, 12:23 AM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
For the main bearing clearances.

I'm getting 0.003 for the thrust bearing and 0.002 for the rest of them.

Does this seem like a good range? If so what oil should I use?
Reply With Quote Quick reply to this message
 
  #4 (permalink)  
Old 09-16-2019, 07:18 AM
Registered User
 
Join Date: Jul 2004
Location: At Speed
Age: 56
Posts: 2,936
Wiki Edits: 0

Thanks: 301
Thanked 419 Times in 369 Posts
those marks won't affect the bearing performance, ignore them.
Reply With Quote Quick reply to this message
The Following 3 Users Say Thank You to lmsport For This Useful Post:
123pugsy (09-16-2019), 64nailhead (09-17-2019), RobbyDD (09-16-2019)
  #5 (permalink)  
Old 09-16-2019, 08:02 AM
Registered User
 
Join Date: Apr 2007
Posts: 12,411
Wiki Edits: 0

Thanks: 183
Thanked 1,144 Times in 914 Posts
The thin coating is Babbitt, it is mostly there to protect the bearing surface beneath from corrosion while in warehouse storage and to provide a sacrificial solid lubrication layer if the initial start up is dry.


Your clearances are correct, the thrust main is a little wider so as to provide lubrication to the thrust surfaces.



You need to check the thrust clearance as well. It is pretty tight at .005 to .007 on the SBC. Lever the shaft back and forth a couple times then hold it in each direction while measuring at the front then back sides of the thrust faces. Measure each side in several places get a strong light in there to observe the mate of the upper and cap side faces they need to be flush with each other if there is a step it will squeegee the oil off and that will wipe out the bearing faces. Be sure to squeeze a bunch of assembly lube in the clearance when you're done measuring and inspecting.


Bogie
Reply With Quote Quick reply to this message
The Following User Says Thank You to BogiesAnnex1 For This Useful Post:
RobbyDD (09-16-2019)
  #6 (permalink)  
Old 09-16-2019, 03:21 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
When you say thrust faces are you talking about the ends of the crank shaft (front and back)? The end of the snout? and the surface that the flywheel bolts to? And then do it 180 degrees on those two positions?

Also should the main caps be torqued to specifications before measurement? Because I watched a video where they were not torqued when they measured this. I thought that was not a proper simulation of the crank if they are not torqued.

Just for understanding purposes why do we put assembly lube on the thrust surface of the bearing? Does this help with break-in?

Is it okay to use engine oil on the main bearings and then assembly lube on the thrust surface?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 09-16-2019, 03:29 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
I realized why I was confused. I was thinking of using a dial indicator compared to feeler gauges.

I have both. What is better? Both?

Also for the inspection of there being a step between the two halfs of the bearing. If I cant notice anything then its okay? And if its noticeable then should I should do some sanding?
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 09-16-2019, 04:10 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
I feel more confident in the feeler gauges. The needle on the dial gauge is touchy.

I have the main caps torqued to like 10 pounds or something. I tapped them into their positions though so they are seated. I'm getting .005. I can put the .005 in but not the .007. So it seems good to me.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 09-16-2019, 05:46 PM
chasracer's Avatar
True Hotrodder
 
Join Date: Oct 2018
Posts: 577
Wiki Edits: 0

Thanks: 40
Thanked 132 Times in 118 Posts
Checking thrust is a multiple step deal. With the bottom bearings in place, I usually put a little white grease on them and drop the crankshaft in place. You should be able to move the crank back and forth by hand or use a good sized screwdriver to lever it back and forth - this should not take a lot of effort. I prefer setting up the dial indicator off the nose of the crankshaft to check. Next you put the caps in place with their bearings and torque everything to spec - ideally you should have the same thrust clearance measurement - if not then something is possibly out of alignment and you need to check that. If for some reason you do not have enough thrust clearance you can sand the thrust surface of the thrust bearing on some wet/dry paper and a sheet of glass - however in all the engines I have built over 50 years now I have never run into that problem. As to your comment about the bearing shell split being off, that sounds like either something isn't clean on the backside or you have an incorrect bearing shell but your clearance measurements should have shown you that already.
Reply With Quote Quick reply to this message
The Following User Says Thank You to chasracer For This Useful Post:
RobbyDD (09-16-2019)
  #10 (permalink)  
Old 09-16-2019, 05:52 PM
Registered User
 
Join Date: Jul 2004
Location: At Speed
Age: 56
Posts: 2,936
Wiki Edits: 0

Thanks: 301
Thanked 419 Times in 369 Posts
set the rear cap by tapping it forward with a dead blow when the cap bolts are just snug, you want to force the cap to the front and align the rear surfaces because all the thrust load comes from the rear(trans)
Reply With Quote Quick reply to this message
The Following User Says Thank You to lmsport For This Useful Post:
RobbyDD (09-16-2019)
  #11 (permalink)  
Old 09-16-2019, 09:24 PM
Registered User
 
Join Date: Apr 2007
Posts: 12,411
Wiki Edits: 0

Thanks: 183
Thanked 1,144 Times in 914 Posts
Quote:
Originally Posted by RobbyDD View Post
I realized why I was confused. I was thinking of using a dial indicator compared to feeler gauges.

I have both. What is better? Both?

Also for the inspection of there being a step between the two halfs of the bearing. If I cant notice anything then its okay? And if its noticeable then should I should do some sanding?
The guys gave you some pretty good insite to this, yes as was said it is a multistep process.

I like to start with the thrust main and bearing assembled by themselves with the main cap torqued to specification. Then inspect the mating surfaces for smoothness at the joint. Lacking that some persuation can be applied or purchase another set of bearings to see if the fit together better.

For the crank, you want to survey the surfaces for smoothness and holding 90 degrees to the journal. The objective is to see that you are starting with is a good surface and things line up, we're not yet concerned with actual clearance.

For actual clearance measurement I dog the main cap fasteners to spec. As far as the tools to measure the clearance I'm not hard over between a dial indicator or feelers. I find feelers easier to use when working by myself as prying on the crank while watching the dial indicator can be an eye test.

Sanding the bearing faces is to widen the clearance if that is necessary.

Bogie
Reply With Quote Quick reply to this message
The Following User Says Thank You to BogiesAnnex1 For This Useful Post:
RobbyDD (09-18-2019)
  #12 (permalink)  
Old 09-17-2019, 04:58 PM
64nailhead's Avatar
Registered User
 
Join Date: Dec 2012
Location: Binghamton, NY
Posts: 3,836
Wiki Edits: 0

Thanks: 1,285
Thanked 967 Times in 801 Posts
Regarding your clearances and the 'mark' - forget the mark - it's nothing and normal. You clearances are fine as well. I'd say run 15W40 or 20W50 with a high volume pump if over .0030".

Where are the rod's clearance at?
Reply With Quote Quick reply to this message
The Following User Says Thank You to 64nailhead For This Useful Post:
RobbyDD (09-18-2019)
  #13 (permalink)  
Old 09-18-2019, 02:40 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
Thanks for the advice! I finally understand.

The crank surfaces are smooth. Its a new eagle crank. There was a bunch of crap in the oiling holes though. Those rifle brushes work great.
I can't measure the connecting rod clearances yet because I need to get a connecting rod vise to take the bolts out of the new connecting rods. I don't understand why I cant use a regular vise with some wood covering the teeth on the vise so it doesn't scratch the big end.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 09-18-2019, 02:44 PM
johnsongrass1's Avatar
Race it, Don't rice it!
 
Join Date: Jul 2002
Location: Columbia, Mo
Age: 43
Posts: 6,949
Wiki Edits: 0

Thanks: 105
Thanked 710 Times in 584 Posts
Quote:
Originally Posted by RobbyDD View Post
Thanks for the advice! I finally understand.

The crank surfaces are smooth. Its a new eagle crank. There was a bunch of crap in the oiling holes though. Those rifle brushes work great.
I can't measure the connecting rod clearances yet because I need to get a connecting rod vise to take the bolts out of the new connecting rods. I don't understand why I cant use a regular vise with some wood covering the teeth on the vise so it doesn't scratch the big end.
I use 1" aluminum angle cut to fit. Works just fine. I've wood and even old rags.
Whatever ya got.
Reply With Quote Quick reply to this message
The Following User Says Thank You to johnsongrass1 For This Useful Post:
RobbyDD (09-18-2019)
  #15 (permalink)  
Old 09-19-2019, 02:45 PM
Registered User
 
Join Date: Oct 2017
Posts: 203
Wiki Edits: 0

Thanks: 110
Thanked 0 Times in 0 Posts
I measured the clearances on the connecting rods. The lowest was 0.0029 and the highest was 0.00325. Also I only measured inline with the I beam on the rod (co-linear to the length of the rod). The measurement was way off if I measured 90 degrees from that. Are the rods supposed to be slightly elliptical?

Also I accidentally dropped one of the bearing shells in some purple power and it changed the color. I made a reaction with the babbit. I used one of those green scots bright pads to remove it, so now its bare metal. Is this still okay to run?
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 12:30 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.