Alot of people doing engines this winter - link inside with good info!
02-16-2008, 11:44 PM
#1
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Alot of people doing engines this winter - link inside with good info!
http://forums.pelicanparts.com/showt...=307291&page=2
50 ftlb on my ARP rod bolts for the 5L are stretching the bolts to .006" or so.
That means I will have to go past the OEM torque spec that Porsche states for THEIR torque to yield bolts for these ARP stretch bolts.
204-6002 is the part number
.0112 is the stretch I should see at whatever torque and leave it there.
50 is the suggested torque, but it could take more than that.
Interesting excerpt for those doing your rod bearings (or in keith's case, looking at them with 144k miles and NOT replacing them
)
50 ftlb on my ARP rod bolts for the 5L are stretching the bolts to .006" or so.
That means I will have to go past the OEM torque spec that Porsche states for THEIR torque to yield bolts for these ARP stretch bolts.
204-6002 is the part number
.0112 is the stretch I should see at whatever torque and leave it there.
50 is the suggested torque, but it could take more than that.
Interesting excerpt for those doing your rod bearings (or in keith's case, looking at them with 144k miles and NOT replacing them
)
3. Torque to angle is another type of bolt and torque or stretch is not used with it. A torque to yield bolt, ie torque to angle is a very good bolt and the one Porsche uses as stock for its rod bolts. It is stretched beyond its yield point, that is, it never returns to its original dimension because its stretched beyond its yield point. It can only be tightened ONE time and it MUST be discarded. It is tightened to a specific torque to take up the slack, then its turned for a specified number of degrees, eg as much as 360 degrees or as little as 50 degrees, depends on the bolt and mfg. The bolt is beyond its yield point yet safely below its breaking point, consequently its at its max clamping power. ITs a super bolt, only problem, you CANNOT retighten one.
02-17-2008, 01:12 AM
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Brendan, sometimes one has to take a step or two back and not listen to all of the suggestions thrown at you. If I (or anyone for that matter) listened to everything that was posted in many threads, I/we would be ordering Johnson Rods from some far off land that has just the right combination of elements from the periodic table.
Take your ARP studs for instance. I can't begin to tell you how unnecessary and a waste of money it is to use those, but Hey, it's your hard earned cash and they will allow you sleep at night . I'll just reused my old tired and stretched out rusty studs
Sometimes we all really do need to back off of what the 100's of non mechanics/engineers on this list preach.
So how much you want to bet me that those bearings on my car will last for years to come and under serious flogging?
If I was a wanna be racer or trying to claim bragging rights of some sort, I would have spent the green to change them. I guess I'll just be the loser that doesn't replace used parts with new ones exceeding Porsche specifications.
02-17-2008, 01:41 AM
#6
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did you spin the oil pump before fitting the T belt??, If you did did you see anything floating aroung the oil cooler lines?
02-17-2008, 02:12 AM
#7
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ARP bolts are a different animal than stock. They have a different heat treating, and a different modulus of elasticity.
If you are using ARP or Precision bolts, use their tightening sequence for maximum performance. If you are using stock bolts, use the Porsche method.
It's interesting that we've picked the rod bolt to discuss, it is under the most stress of any bolt in the engine. Follow instructions carefully.
If you are using ARP or Precision bolts, use their tightening sequence for maximum performance. If you are using stock bolts, use the Porsche method.
It's interesting that we've picked the rod bolt to discuss, it is under the most stress of any bolt in the engine. Follow instructions carefully.
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02-17-2008, 02:26 AM
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02-17-2008, 02:28 AM
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I was just sharing a thread i found, and it was interesting that I have heard and read before that Porsche rod bolts on our cars are a one-time deal.
Brendan, sometimes one has to take a step or two back and not listen to all of the suggestions thrown at you. If I (or anyone for that matter) listened to everything that was posted in many threads, I/we would be ordering Johnson Rods from some far off land that has just the right combination of elements from the periodic table.
Take your ARP studs for instance. I can't begin to tell you how unnecessary and a waste of money it is to use those, but Hey, it's your hard earned cash and they will allow you sleep at night . I'll just reused my old tired and stretched out rusty studs
Sometimes we all really do need to back off of what the 100's of non mechanics/engineers on this list preach.
So how much you want to bet me that those bearings on my car will last for years to come and under serious flogging?
If I was a wanna be racer or trying to claim bragging rights of some sort, I would have spent the green to change them. I guess I'll just be the loser that doesn't replace used parts with new ones exceeding Porsche specifications.
Brendan, sometimes one has to take a step or two back and not listen to all of the suggestions thrown at you. If I (or anyone for that matter) listened to everything that was posted in many threads, I/we would be ordering Johnson Rods from some far off land that has just the right combination of elements from the periodic table.
Take your ARP studs for instance. I can't begin to tell you how unnecessary and a waste of money it is to use those, but Hey, it's your hard earned cash and they will allow you sleep at night . I'll just reused my old tired and stretched out rusty studs
Sometimes we all really do need to back off of what the 100's of non mechanics/engineers on this list preach.
So how much you want to bet me that those bearings on my car will last for years to come and under serious flogging?
If I was a wanna be racer or trying to claim bragging rights of some sort, I would have spent the green to change them. I guess I'll just be the loser that doesn't replace used parts with new ones exceeding Porsche specifications.
02-17-2008, 02:29 AM
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02-17-2008, 02:30 AM
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02-17-2008, 04:09 AM
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Has anyone had an engine failure directly attributable and with the primary cause being rod bolt/stud/nut failure on a 928 engine using stock bolts/studs/nuts ?
Didn't think so.
If I am not mistaken 928 Rod studs are grade 8.8 - they aren't "stretch bolts" The rod nuts are one time use only because of the serrated pattern in the seat of the nut to prevent them undoing.
ARP rods are generally advertised as being much higher strength steel the stock - no argument there. They are only useful if the engine is going to see higher revs than stock as that is the only way that the rod studs/bolts/nuts actually sees higher forces than a stock engine.
In general increasing the displacement or forcing the aspiration (supercharger or turbo or nitrous) does not increase the forces to which the rod studs are subjected at all. Increasing the CR increases the forces on the rod studs but wether this is significant is debatable.
I can't imagine why one would use "stretch" bolts on a rod it wouldn't serve any purpose.
Didn't think so.
If I am not mistaken 928 Rod studs are grade 8.8 - they aren't "stretch bolts" The rod nuts are one time use only because of the serrated pattern in the seat of the nut to prevent them undoing.
ARP rods are generally advertised as being much higher strength steel the stock - no argument there. They are only useful if the engine is going to see higher revs than stock as that is the only way that the rod studs/bolts/nuts actually sees higher forces than a stock engine.
In general increasing the displacement or forcing the aspiration (supercharger or turbo or nitrous) does not increase the forces to which the rod studs are subjected at all. Increasing the CR increases the forces on the rod studs but wether this is significant is debatable.
I can't imagine why one would use "stretch" bolts on a rod it wouldn't serve any purpose.
02-17-2008, 04:27 AM
#14
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The quote that Brendan includes in the first post mixes torque to yield and torque to angle as if they are exactly the same thing. This is not accurate, although very commonly seen this way. Torque to yield stretches the bolt to a point such that it will not return to its original length. Torque to angle does not necessarily stretch to the yield point unless the procedure is designed to do so. Our rod and head bolts are not single use torque to yield.
Oilver uses torque to angle on their rod bolts and makes a clear distinction that this is not torque to yield, if you follow their procedure, and that the bolts are re-usable.
Oilver uses torque to angle on their rod bolts and makes a clear distinction that this is not torque to yield, if you follow their procedure, and that the bolts are re-usable.