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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 80fbody]
#1560815
01/08/14 03:06 PM
01/08/14 03:06 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
I have a bore gauge already & am considering an outside mic purchase.
Question is: Do you install the bearings in the main bores, torque to specs & then run the bore gauge inside the bearings? Or, would you measure the bearing shells separately.
I put the bearings in and torque them then take the
reading
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: Performance Only]
#1560818
01/08/14 03:58 PM
01/08/14 03:58 PM
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Joined: Oct 2003
Posts: 11,684
W. Kentucky
justinp61
I Live Here
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I Live Here
Joined: Oct 2003
Posts: 11,684
W. Kentucky
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Quote:
Yes, Mic the crank journals (each one in case some are different), set the bore guage to the mic, then measure the clearance with the bearings torqued in the mains.
 That's the way I do mine. Rods too.
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 80fbody]
#1560820
01/08/14 04:47 PM
01/08/14 04:47 PM
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Joined: Jan 2003
Posts: 10,010
Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,010
Frostbitefalls MN (Rocky&Bullw...
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The measurements should come up consistent across the bearings, (side to side at the bottom and top) but if you get odd readings, pull the bearings and check the bearing bores with the caps properly torqued. I had main bearing bores that were off by .0005 and it showed up in the bearing readings off by the same .0005 from one side of the bearing to the other.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 408cuda]
#1560826
01/09/14 06:02 AM
01/09/14 06:02 AM
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Joined: May 2008
Posts: 5,399
Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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Quote:
I do it both ways. Can't hurt. Always comes out bigger with shells in place for me. Like Dan said set the bore gauge so there is very little tension, like the end of its travel while having enough to cover your clearance range.
Bearing shells have eccentricity and are taper at the parting line to allow for mismatching of parts slightly as I understand it. Clearance out there is usually high and most say not to bother checking. I record it while I'm in there. Good info for future reference and you never you know when you might catch something. All part of balance and blue printing 
If you measure the bore without bearings, you can compare that to the bearing spec to make sure the bearings are not too loose or tight in the bore. If the bore clearance is correct, the inside bearing diameter should also be correct for the specified bearing clearance unless you have bearings that are out of specification. If the crank is the correct diameter then and the bearings and bore are correct, the oil clearance should also be correct. The real issue is calibration standards, or lack of their use. So anyhow it is always best to perform a differential check for the crank to bearing oil clearance as described earlier in the posts - measuring the crank and setting the dialbore gauge to that size, then just check how much larger the bearing bore size is compared to the crank.
Below is the main bearing specs for Clevite 77 440 big block main bearings.
Clevite 77 MS-1795 440 main bearing set.
Bearings 1,2,4,5 - MB-3248V
Bearing 3 - MB-3248V(F)
Shaft diameter (Crank) = 2.7500" +/- 0.0005"
Oil Clearance min = 0.0005", max = 0.0026"
Max bearing thickness = 0.09590"
Housing Bore (block) - min = 2.9425, max = 2.9430"
Max bearing width (1,2,4,5) = 0.9490", (#3) = 1.2240"
Last edited by 451Mopar; 01/09/14 06:13 AM.
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 80fbody]
#1560828
01/09/14 11:56 AM
01/09/14 11:56 AM
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Joined: Jan 2003
Posts: 10,010
Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,010
Frostbitefalls MN (Rocky&Bullw...
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Quote:
Greg, did that require a cut/hone on the mains? Just curious in case I come across something similar. My block was line honed & studded but never run. Definitely want to make sure work was done properly.
After having it line honed, it came back that way! I wonder if the block was close and the guy on the machine didn't line bore it? I got charged for it though.
My fix was to use 200 sand paper and a flat plate to remove the machine marks (slowly, checking more than a couple of times) one the high side of the offending caps. It took a couple of hours, but it was quicker than taking it back and asking to have it done right. If you aren't confident in that kind of a fix, I would take the block in and tell them what you measured, and ask that it be fixed. Also the bearing crush dimension should be on the small side, or in the middle, but not too loose. That will also affect the bearing measurements. This thread is getting some good info out there, and if the OP doesn't mind, any other tips the pros on hear want to add?
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 80fbody]
#1560830
01/09/14 09:09 PM
01/09/14 09:09 PM
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Joined: Jan 2003
Posts: 7,494
Minnesota
Hemi_Joel
master
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master
Joined: Jan 2003
Posts: 7,494
Minnesota
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Make sure that your new mikes are graduated .0001". You say you already have a dial bore guage, hopefully it is also .0001". The .001 mikes and the .0005 DBG's leave you with the need for guesswork.  Have fun!
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 80fbody]
#1560832
01/10/14 06:16 AM
01/10/14 06:16 AM
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Joined: Mar 2008
Posts: 883
Affton MO
qwkmopardan
super stock
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super stock
Joined: Mar 2008
Posts: 883
Affton MO
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I don't like using a bore guage in the bearings as it almost allways scratches the bearing. I have a ball micrometer, and measure the thickness of each bearing shell. Most of the time the bearings vary, as much as .0002". Then measure the crank, all journals, two spots on the rods, center of where each bearing rides. A lot of times there is .0001/.0002 taper. I have never seen a crank where all jrnls measure all the same. The better ones are within .0001"/.0002". Then use a bore gauge to check main bores and each rod. Write all your measurements in a notebook. After you have all your measurements you can find the clearances and fine tune them, a lot of times, by strategically placing the thick and thin bearings. On the rods you can pick and choose which journal and thick or thin bearing, to place each rod. you can equalize the clearances a lot better using this method.
On the mains, if you have .0002" variance in the bores and .0002" variance on the jrnls. on the crank, and .0002 variance on bearing, and you end up with the smallest bore with the biggest jrnl on crank, you can put the thinner shell in that spot. This is more important if running tighter clearances. Of course the #3 bearing on a BBM and #3 and #5 on SBM you can't be selective.
Also if you have the block align honed to the low side, BB Mopar example, 2.9425" and the crank ground to the high side, 2.7505", minus your undersize, and the bearings near the max wall thickness, which they almost allways are for the Mopar aplications, you will have only .0002 clearance. Similar problem on the rods. Almost allways when I have a Chrysler crank reground it is .011"/ .0115" undersize, not .010. Now a days I usually order the bearings first and measure the thickness of each bearing, and then give the crank grinder the size I want the jrnls.
A engine a little to tight can have big problems, an engine a little to loose will run its a$$ off and live.
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Re: Measuring Main/Rod Clearance With Bore Gauge?
[Re: 80fbody]
#1560833
01/10/14 06:17 AM
01/10/14 06:17 AM
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Joined: Mar 2008
Posts: 883
Affton MO
qwkmopardan
super stock
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super stock
Joined: Mar 2008
Posts: 883
Affton MO
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Quote:
The new mic is .0001 & the bore gauge is .0005 . Hopefully that will work. I never thought about bearings when I originally bought the gauge. I could probably get a .0001 gauge if really needed.
You can use the .0005 gauge. You will just have to read between the lines.
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I've seen a lot of rods amd main bearings have more oil clearances at the bearing parting lines than at 90 degrees to them 
Never had a problem running them that way either 
