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06-18-2017, 07:45 PM | #1 |
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Connecting Rod Clearances
Looking for thoughts on how to fix a recent problem. I have dial bore gaged and verified with plastigage that I am seeing .001 clearance on connecting rod journals.
I have looked to find a .001X oversize bearing to increase the clearance. However the connecting rod journals are ground .030 and manufacturers do not make an oversize bearing at this size. Any ideas on how to open the connecting rod clearance up to .0015-.0020? Can the crank be ground down by .0005 to open the clearance? If so any recommendations on who can do so? Thank you in advance! |
06-18-2017, 08:55 PM | #2 |
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Re: Connecting Rod Clearances
the rod housing bore could be on the small side of that tolerance...
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06-19-2017, 07:08 AM | #3 |
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Re: Connecting Rod Clearances
Try a different brand of bearings. I think it's best to size the rod, instal bearings, subtract clearance, then resize crank. Also look at the backside of bearing for for bruses in the metal, trash inbeded on the back side, or flash from a plating. Almost forgot, check the tang fit.
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06-19-2017, 08:17 AM | #4 |
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Re: Connecting Rod Clearances
Use micrometers - inside and outside. Plastigage will not give you accurate measurements. Waste of time and effort.
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06-19-2017, 02:48 PM | #5 |
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Re: Connecting Rod Clearances
Yes to all of the above.
Don't use plastigage. The connecting Rod Bores can be resized to the high side of tolerance. They at least need to be clean ,straight and round. Different Bearing manufacturers do vary in size as Mr. Hill stated. In my findings Clevite 77 are the tightest fit, Speed Pro / Federal Mogul tends to be about .0001 to .00015" bigger and recently I have been seeing King XP bearings closer to .0002" or more than a Clevite.
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Todd Gross 3323 FS/E,F |
06-25-2017, 09:25 AM | #6 |
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Re: Connecting Rod Clearances
So what did you do?
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06-25-2017, 10:50 AM | #7 | |
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Re: Connecting Rod Clearances
Quote:
I have guys check my clearances with it seem to right in line with what I set them at with my Sunnen Bore gauge. Here is are some good threads on checking bearing clearances. http://www.performanceboats.com/gn7-...learances.html http://www.speedtalk.com/forum/viewt...a58c2&start=15 Last edited by carl hinkson; 06-25-2017 at 11:05 AM. |
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06-26-2017, 09:21 PM | #8 |
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Re: Connecting Rod Clearances
Follow Up
I found on a past classracer post that is very difficult to take a few tenths off a connecting rod journal. http://www.classracer.com/classforum...ad.php?t=53273 These were the other options I looked at: 1) Polish connecting rod journal 2) Hone Rod Big End 3) Grind Crank to .040 Under In the end swapped to another crank rather than risking any of the above options. Thanks for the advice! |
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