Crank Bearing Question
03-20-2004, 08:05 AM
#1
Banned
Thread Starter
Join Date: Feb 2004
Location: In self-imposed exile.
Posts: 14,072
Likes: 0
Received 8 Likes
on
7 Posts
Crank Bearing Question
OK, I keep hearing this term "spun bearing" thrown around, mostly in reference to the #2 cylinder on our 944 engines. What exactly does this term mean? I think it is related to poor oiling of the junction of the connecting rod and crankshaft journal, but I've just never gotten a complete explaination of the term. Does that crank journal area just overheat and start siezing up or what?
03-21-2004, 03:57 PM
#2
Addict
Rennlist Member
Rennlist Member
Join Date: Feb 2004
Location: SW Ontario canada
Posts: 882
Likes: 0
Received 0 Likes
on
0 Posts
Oil cools as well as lubricates. Insufficent oil=heat=seizure. The bearing and crank become one and the bearing turns in the rod.
Most agree the root cause is the oil sloshing away from the oil pickup in hard cornering, leaving the pump nothing but air. I am not sure what causes the #2 rod bearing to be the first to fail from it.
Hope this gets you started. For moe detail, do a search. there is alot written about this
Most agree the root cause is the oil sloshing away from the oil pickup in hard cornering, leaving the pump nothing but air. I am not sure what causes the #2 rod bearing to be the first to fail from it.
Hope this gets you started. For moe detail, do a search. there is alot written about this
03-22-2004, 04:45 AM
#3
Race Director
"Most agree the root cause is the oil sloshing away from the oil pickup in hard cornering, leaving the pump nothing but air. I am not sure what causes the #2 rod bearing to be the first to fail from it."
Actually no one really knows the exact cause for sure because they can't explain why it's the #2 that goes first. All 5 mains gets an oil feed and it goes through the crank to get to the rod-journals. So the #2 rod is fed on both sides by the #1 & #2 mains.
What is known, are mods to help reduce the #2 vulnerability. THese include upgrading to the latest oil-pan baffle that has an extra barrier to reduce lateral sloshing as well as working as a better scraper. Then there's the filling-over by 1-quart trick. And the lowering of the sides of the pick-up tube to suck oil from lower down in the pan. Then there's the cross-drill and perp-drill mods. Personally, I like the perp drill the best where it places a new hole on the very outer edge of the rod-journal so that centripedal spinning forces will force oil out of the journal. This is how all the high-revving motorycle engines I've ever seen are drilled, on the outside of the journal, no on the side like Porsche did... bizarre...
Actually no one really knows the exact cause for sure because they can't explain why it's the #2 that goes first. All 5 mains gets an oil feed and it goes through the crank to get to the rod-journals. So the #2 rod is fed on both sides by the #1 & #2 mains.
What is known, are mods to help reduce the #2 vulnerability. THese include upgrading to the latest oil-pan baffle that has an extra barrier to reduce lateral sloshing as well as working as a better scraper. Then there's the filling-over by 1-quart trick. And the lowering of the sides of the pick-up tube to suck oil from lower down in the pan. Then there's the cross-drill and perp-drill mods. Personally, I like the perp drill the best where it places a new hole on the very outer edge of the rod-journal so that centripedal spinning forces will force oil out of the journal. This is how all the high-revving motorycle engines I've ever seen are drilled, on the outside of the journal, no on the side like Porsche did... bizarre...
Last edited by Danno; 03-22-2004 at 05:01 AM.
03-26-2004, 06:24 PM
#4
So if one were say going into a 150,000 mile engine to try the "paragon" rod bearing replacement while the engine is still in the car method. One could in theory do everything i.e. put baffles in the oil pan and cut down the side of the pick up tube yes? Now to cross drill the crank it would have to come out?
IPSC (learning just enough to be dangerous)
IPSC (learning just enough to be dangerous)
