50 Track Hour Rod Bearing Change
12-14-2001 | 01:14 AM
#19
Addict
Rennlist Member
Rennlist Member
Joined: May 2001
Posts: 6,915
Likes: 70
From: Kansas City
Well.. I have the 2 peice crossover.
Everyone says the 1 peice is a pain, but why not just un-bolt at the headers, at the turbo, and lower the entire exhaust system with it?. You only need about 4" of clearance! No need to remove it.
Everyone says the 1 peice is a pain, but why not just un-bolt at the headers, at the turbo, and lower the entire exhaust system with it?. You only need about 4" of clearance! No need to remove it.
12-14-2001 | 03:19 PM
#20
Instructor
Joined: Jul 2001
Posts: 170
Likes: 0
From: New Hampshire
Well, I'll try to throw in my $.02 on the #2 bearing failures. I'm not an expert on the layout of the oiling system/passages in a 944, so the comparisons I make below may/may not apply.
I suspect the #2 bearing is like the new home owner who lives in the new development on the edge of town ... the furthest from the pumping station. In general, water pressure is OK, but not nearly as good as the folks down near the pumping station. The problem really becomes apparent when drought comes, the water table gets low, and pressures drop. The poor guy furthest from the pump only gets a trickle out of his faucet. This is similar to how life is in your oiling system.
Remember, your oil pressue gauge measures pressure at the source near the oil pump. After winding it's way thru all the galleries in the block, crank, head, and cam assy you can expect some areas to have higher/lower pressures than others. When you throw in an additional oil starvation problem due to the sump sucking air, and those "low" pressure areas go even lower. Go even further, and combine that with all the energy being transfered at that now somewhat "dry" rod journal/bearing interface and you're destined to have higher than normal wear ... to the possible extent of massive bearing failure if the condition is repeated enough times or long enough.
Though it's not Porsche powered, I've been driving Formula Vee for quite a few years, and we've got the same problem ... #2 rod bearing. Oil starvation is the same cause.
If you don't keep an eye on oil levels, you chew up #2. Some tracks aggrivate the issue more. The reason #2 goes is because it's the bearing "furthest" from the pump (relative to the other bearings).
-Bob P (bit by #2 while leading at NHIS in '99)
I suspect the #2 bearing is like the new home owner who lives in the new development on the edge of town ... the furthest from the pumping station. In general, water pressure is OK, but not nearly as good as the folks down near the pumping station. The problem really becomes apparent when drought comes, the water table gets low, and pressures drop. The poor guy furthest from the pump only gets a trickle out of his faucet. This is similar to how life is in your oiling system.
Remember, your oil pressue gauge measures pressure at the source near the oil pump. After winding it's way thru all the galleries in the block, crank, head, and cam assy you can expect some areas to have higher/lower pressures than others. When you throw in an additional oil starvation problem due to the sump sucking air, and those "low" pressure areas go even lower. Go even further, and combine that with all the energy being transfered at that now somewhat "dry" rod journal/bearing interface and you're destined to have higher than normal wear ... to the possible extent of massive bearing failure if the condition is repeated enough times or long enough.
Though it's not Porsche powered, I've been driving Formula Vee for quite a few years, and we've got the same problem ... #2 rod bearing. Oil starvation is the same cause.
If you don't keep an eye on oil levels, you chew up #2. Some tracks aggrivate the issue more. The reason #2 goes is because it's the bearing "furthest" from the pump (relative to the other bearings).
-Bob P (bit by #2 while leading at NHIS in '99)
