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snowman snowman is offline
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Join Date: Feb 2003
Location: So California
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Rod bearing analysis of race engine

The following photos are of the rod bearings in my 912 race car engine. They are after 25 hours of 8000 rpm plus operation and at least a couple of excursions to 10,000 rpm!. The overall condition is excellent, ie the initial bearing clearence was 2.4 thousands, and the final 2.6 thousands of an inch. Note even the tin plating is still visible over a large part of the bearing.

HOWEVER also note the small area where "worms" are starting to grow in the bearing. At this point I attribute the smallness of the worm area to the following:
Redline race oil, 30 wt
Scat Crankshaft
Near perfact engine balance

On earlier engines I have done, using original Porsche cranks and regular race oil and Mobil 1 type oils, I have seen the worms grow to half the rod bearing area in the same amount of time at slightly lower rpms.

Is this improvement due to:
1 Redline oil
2 Scat crank
3. both
4. small sample size
5. other

Heres the pictures:


My theory is that the pressure is so great that the bearing is overloaded. In other words the oil pressure from the load pushes so hard on the bearing material that it acutally starts to seperate it from itself, causing the "worming" effect. Or simply bearing overload. Solution is for a larger bearing surface or stronger bearing material. Thats my GUESS. So what say the metal people that know what they are talking about??
Old 11-08-2005, 08:21 PM
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