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Registered
Join Date: Jul 2003
Location: Richmond, Virginia
Posts: 112
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Crankshaft tolerance and #1 bearing
I am rebuilding a Porsche 3.0 litre from my '79 911SC and I am concerned about the extraordinary wear on the thrust edge of my #1 main bearing. It appears that the crankshaft, when installed in the case, has a significant amount of tolerance that may allow the crankshaft to "walk" front to rear which may be creating this extra wear on the #1 bearing, as well as potentially cause additional stress and wear on my connecting rods and those bearings and pistons and cylinders. Is there a reason for this excess tolerance or is there a manufacturer that may be able to provide a #1 bearing with a thicker thrust edge? Or am I destined to continually breakdown this engine to replace that bearing? Thanks, Duane
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'79 911SC Targa -- "BLUVUDU" '83 930 Coupe -- "TURBAUX" |
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07-08-2003, 09:33 AM
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PRO Motorsports
Join Date: Nov 2001
Location: Burbank, CA
Posts: 4,580
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If I remember correctly, some of the early SC engines had issues with improper hardening of the crankshaft, which resulted in the thrust surfaces of the crank wearing out prematurely.
Send the crank to a Porsche-savvy machinist who can check the dimensions of your crankshaft. I don't believe there are oversized thrust bearings that can compensate for excessive thrust clearance.
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'69 911E coupe' RSR clone-in-progress (retired 911-Spec racer) '72 911T Targa MFI 2.4E spec(Formerly "Scruffy") 2004 GT3 |
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07-08-2003, 11:45 PM
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