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Join Date: Apr 2003
Location: Gilroy, CA
Posts: 340
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Help - Main Bearing problem
The center Main bearing went bad in a new 2.0 motor.
The problem is that only one of the bearing shells went to copper. The other shell is OK. Also the surface of the bad shell went bad only on one edge. Case had been bored "20 over" & crank had been checked and polished. All new bearings. I hope the attached picture shows enough detail. Has anybody had this problem and found a solution?? Ken 
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06-21-2003, 04:09 PM
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Join Date: Sep 2001
Location: Crestline, CA
Posts: 937
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Fillet radius on the crank was ground incorrectly as in not large enough!
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"Inventor - Blue Flame 914 Seat Heater" "Yellow Rusty Cars Are Faster" _____________________________ '70 2.5 (I'll never finish it - Somewhere over the rainbow.....,) '73 2.0 (Just Not The Same) '74 2.0 (Heartless & Lungless) |
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06-22-2003, 08:13 PM
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Join Date: Jan 2001
Posts: 400
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incorrectly torqued main bolts
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scott thacher 75 914 with 2.5 l 98 suby engine on the road |
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06-23-2003, 05:41 PM
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Location: Gilroy, CA
Posts: 340
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Problem FOUND.
Plastigage shows bearing not flat. Bulged end is less than 0.001". Other side consitant 0.0015/.002. Note grease was used on the good side to keep the Plastigage in place. I do not know how common this is, but I will always use Plastgae from now on. Ken 
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07-12-2003, 01:03 PM
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how about a little lesson on when and where and how to use plastigage. i didn't use it on my first rebuild. had all machine work done, measured and assumed all was good. engine was 81 vanagon 2L.
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73 914 restoration project 73 914 2.0 CIS #80 74 914 1.8L L-jet 83 911SC |
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07-12-2003, 07:29 PM
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Location: Gilroy, CA
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Plastigage is a small plastic strip that can be obtained from most auto stores who supply local auto mechanics.
It comes in various sizes depending on the clearence to be measured. It is placed on the bearing, or shaft. In the case on a 914 main bearing, the case is put together and torque to specifiction. If it were a rod, then the cap would be put on and torqued. Becareful not to rotate the shaft as that would smear the plastigage. You then take the case apart and measure the spread of the Plastigage. A scale is printed on the package that shows the clearence depending on how wide the Plastigage is. Ken 
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07-13-2003, 07:59 AM
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Join Date: Jan 2002
Location: Long Beach CA, the sewer by the sea.
Posts: 37,760
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Ken, are you sure that's it? No problems with the main bearing saddle that Jake Raby is always talking about?
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07-13-2003, 04:45 PM
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Location: Gilroy, CA
Posts: 340
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Milt,
I had the shop that did the line bore look at the case as well as check the crank. They is was OK. The other half of the bearing was 0.002 across the FULL surface. This side was 0.0015 to < 0.001. I would think a saddle probelm would show up on both sides. I will Plasigage it again with new bearings, sometime this week. I will add to this post what I find out. Ken
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Anything worth doing is worth doing in excess Every silver lining has a cloud Assume Nothing |
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07-14-2003, 06:58 AM
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Join Date: Feb 2001
Location: Aircooled Heaven
Posts: 1,054
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Sounds like you have a "Collapsed" center main........I see this often.
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Jake Raby Owner, Raby's Aircooled Technology www.aircooledtechnology.com www.massivetype4.com |
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07-14-2003, 02:18 PM
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orange
