Minimizing #2 rod failure after engine rebuild
03-20-2016, 09:52 AM
#1
Minimizing #2 rod failure after engine rebuild
This has been discussed many times, but usually all threads are side tracked. I will try to summarize what I have learned in other threads.
Some information about my car and its planned application.
I am in a middle my 87 951 engine refresh/rebuild. The car originally was delivered to customer only in November 88 in Switzerland. I purchased in end of 2013 with 140k miles on it. The car is/will be driven in weekends and will see track day 5 – 6 time each year. It already has some suspension modifications, but it will not be a track car.
Some details about the engine/car:
It will have standard 2.5 block and head. I will put on rebuilt and modified k26/6 running 1.1 to 1.2 bar with VEMS and Siemens DEKA 630cc injectors. The car has full 3 inch DP and cat less exhaust with Magnaflow resonators. I will also use APR head studs, Wossner rods, new seals top and bottom, valve springs and some other parts, including KEP Stage 1 PP and Sachs HD clutch disk.
The cylinder walls look fine (although not ideal), the crank also does not have any scratches, the #2 bearing shows some usage signs the same as #1 main bearing.
The reason I started this thread is to ask about modifications that could be done to deal with the #2 and 3 rod bearing failure. Considering that the car will see track I would like to do some homework. Have seen many threads about his topic and the brief summary is:
1) Cross or perpendicular drilling of the crank will not help much to deal with this issue, so I am not doing it;
2) Will do micro polish of the crank when installing new bearings;
3) The clearance of the rod bearings is important and it is advisable to have little bit bigger clearance on #2 (.003" (minimum) clearance on #2), but as I will use STD Glyco bearings, I do not have any room to play, as they all come in one size.
4) Reduction of the oil foaming is important – will use appropriate oil (Millers 10w50 or 10w60 race oil). Viscosity and additives are important.
5) Will install Teflon crank scraper that I got from Paragon Products. The car already has updated oil pan baffle with OEM “crank scraper” that should also help little bit against oil foaming.
6) Keeping oil temperature down on track is important to retain higher viscosity of the oil, so I will put additional oil cooler in the area of front fender.
7) Will not use oil pan baffle, as don’t see how that would help me on 16 inch semi slick tires.
8) Putting other harder rod bearings (good mod, but I will not do it). You would need to modify the rods, but in case anything isn’t right, you would have greater risk of losing your crank.
9) Coating the bearings.
10) Will install the oil pick-up tube extension ring to reduce risk of sucking in air.
11) Maybe will relocate the oil return line so that it is not right next to the pick-up tube, but this might create some other issues, so still debating about that.
12) Will add so called “windage ports” to reduce some oil foaming, but this mod is lees related to the #2 rad bearing issue.
13) Try to not rew the engine above 6000 rpm – hard to do on a track when you try to set personal best lap
I have seen tests related to the #2 rod bearing issues where results showed that 50% of oil is supplied to #1 rod, 25% to #4 and the remaining part is split between #2 and #3 (#2 seemingly receiving smallest part of those remaining 25%). To deal with it, some 944 and 928 engine builders have suggested the following:
Drilling #3 main and sending that oil to #2 and #3 rod will help. You need to modify the #3 main bearing to provide an oil path, if this is done. It can be full grooved, but will work better if it looks like the "other bearings".
Has anyone ever heard of this mod and if yes, I would appreciate any tips or pictures how this mod should be properly performed.
Other suggestions are welcomed.
Some information about my car and its planned application.
I am in a middle my 87 951 engine refresh/rebuild. The car originally was delivered to customer only in November 88 in Switzerland. I purchased in end of 2013 with 140k miles on it. The car is/will be driven in weekends and will see track day 5 – 6 time each year. It already has some suspension modifications, but it will not be a track car.
Some details about the engine/car:
It will have standard 2.5 block and head. I will put on rebuilt and modified k26/6 running 1.1 to 1.2 bar with VEMS and Siemens DEKA 630cc injectors. The car has full 3 inch DP and cat less exhaust with Magnaflow resonators. I will also use APR head studs, Wossner rods, new seals top and bottom, valve springs and some other parts, including KEP Stage 1 PP and Sachs HD clutch disk.
The cylinder walls look fine (although not ideal), the crank also does not have any scratches, the #2 bearing shows some usage signs the same as #1 main bearing.
The reason I started this thread is to ask about modifications that could be done to deal with the #2 and 3 rod bearing failure. Considering that the car will see track I would like to do some homework. Have seen many threads about his topic and the brief summary is:
1) Cross or perpendicular drilling of the crank will not help much to deal with this issue, so I am not doing it;
2) Will do micro polish of the crank when installing new bearings;
3) The clearance of the rod bearings is important and it is advisable to have little bit bigger clearance on #2 (.003" (minimum) clearance on #2), but as I will use STD Glyco bearings, I do not have any room to play, as they all come in one size.
4) Reduction of the oil foaming is important – will use appropriate oil (Millers 10w50 or 10w60 race oil). Viscosity and additives are important.
5) Will install Teflon crank scraper that I got from Paragon Products. The car already has updated oil pan baffle with OEM “crank scraper” that should also help little bit against oil foaming.
6) Keeping oil temperature down on track is important to retain higher viscosity of the oil, so I will put additional oil cooler in the area of front fender.
7) Will not use oil pan baffle, as don’t see how that would help me on 16 inch semi slick tires.
8) Putting other harder rod bearings (good mod, but I will not do it). You would need to modify the rods, but in case anything isn’t right, you would have greater risk of losing your crank.
9) Coating the bearings.
10) Will install the oil pick-up tube extension ring to reduce risk of sucking in air.
11) Maybe will relocate the oil return line so that it is not right next to the pick-up tube, but this might create some other issues, so still debating about that.
12) Will add so called “windage ports” to reduce some oil foaming, but this mod is lees related to the #2 rad bearing issue.
13) Try to not rew the engine above 6000 rpm – hard to do on a track when you try to set personal best lap
I have seen tests related to the #2 rod bearing issues where results showed that 50% of oil is supplied to #1 rod, 25% to #4 and the remaining part is split between #2 and #3 (#2 seemingly receiving smallest part of those remaining 25%). To deal with it, some 944 and 928 engine builders have suggested the following:
Drilling #3 main and sending that oil to #2 and #3 rod will help. You need to modify the #3 main bearing to provide an oil path, if this is done. It can be full grooved, but will work better if it looks like the "other bearings".
Has anyone ever heard of this mod and if yes, I would appreciate any tips or pictures how this mod should be properly performed.
Other suggestions are welcomed.
03-20-2016, 12:40 PM
#2
Michael Mount has an excellent Rod bearing mod that he offers.
You can find about it by doing a search here on RL.
You can find about it by doing a search here on RL.
03-20-2016, 01:18 PM
#3
Rennlist Member
Is this failure related to oil starvation or coolant in the oil? I just picked up an 87 951 also and I am debating whether or not to do this now or wait until next fall/winter to pull the engine. Unfortunately I have no records on the car from the PO, but last reported mileage was 203k but the cluster has 135k, most likely someone changed it. I'm looking more or less for a cruiser with the possibility of taking it to work often.
If the bearings only come in one size does it make sense to plastigauge them?if I change them in the car then I wouldn't be able to pull the crank, another reason I figured I'd like to wait
If the bearings only come in one size does it make sense to plastigauge them?if I change them in the car then I wouldn't be able to pull the crank, another reason I figured I'd like to wait
03-20-2016, 01:27 PM
#4
Thanks for suggestion. I know about that mod, but as stated above I will not do it. I would have to send my Wossner rods to US from Europe where I am located, and most probably I would have to pay about 500 USD in only shipping and custom/VAT duties + cost of the mod + it would take a lot of time and the engine would not be ready for the season opening event 
And that mod does not deal with the oiling issue of #2 - it puts stronger bearings instead of the Clyco soft ones.
And that mod does not deal with the oiling issue of #2 - it puts stronger bearings instead of the Clyco soft ones.
03-20-2016, 01:32 PM
#5
Is this failure related to oil starvation or coolant in the oil? I just picked up an 87 951 also and I am debating whether or not to do this now or wait until next fall/winter to pull the engine. Unfortunately I have no records on the car from the PO, but last reported mileage was 203k but the cluster has 135k, most likely someone changed it. I'm looking more or less for a cruiser with the possibility of taking it to work often.
If the bearings only come in one size does it make sense to plastigauge them?if I change them in the car then I wouldn't be able to pull the crank, another reason I figured I'd like to wait
If the bearings only come in one size does it make sense to plastigauge them?if I change them in the car then I wouldn't be able to pull the crank, another reason I figured I'd like to wait
03-20-2016, 01:42 PM
#6
Rennlist Member
Thanks for reply Smudo, that seems like an odd design to have the oil flow like that. Is the mod to the 3rd main difficult or can a diy mech do it?
03-20-2016, 02:04 PM
#7
In theory it should not be hard if you have the tools and knowledge, but there is almost no information about this mod on internet.
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03-20-2016, 02:12 PM
#8
Rennlist Member
That is crazy, this seems to be an ongoing issue with these engines, one would think someone has come up with a solution over the course of the past 33 years this engine has been around! 🤔
03-20-2016, 06:28 PM
#9
Why not just use the stock forged Rarst rods then you can use MM's rod mod?
03-21-2016, 02:31 AM
#11
Did research on internet and did found out that 911 guys are doing similar mods already for long time without complaints. They are revving their race engines over 8000 rpms.
http://forums.pelicanparts.com/911-e...ing-crank.html
http://forums.pelicanparts.com/911-e...ing-crank.html
03-21-2016, 02:34 AM
#12
03-21-2016, 03:35 PM
#13
Rennlist Member
This has been discussed many times, but usually all threads are side tracked. I will try to summarize what I have learned in other threads.
Some information about my car and its planned application.
I am in a middle my 87 951 engine refresh/rebuild. The car originally was delivered to customer only in November 88 in Switzerland. I purchased in end of 2013 with 140k miles on it. The car is/will be driven in weekends and will see track day 5 – 6 time each year. It already has some suspension modifications, but it will not be a track car.
Some details about the engine/car:
It will have standard 2.5 block and head. I will put on rebuilt and modified k26/6 running 1.1 to 1.2 bar with VEMS and Siemens DEKA 630cc injectors. The car has full 3 inch DP and cat less exhaust with Magnaflow resonators. I will also use APR head studs, Wossner rods, new seals top and bottom, valve springs and some other parts, including KEP Stage 1 PP and Sachs HD clutch disk.
The cylinder walls look fine (although not ideal), the crank also does not have any scratches, the #2 bearing shows some usage signs the same as #1 main bearing.
The reason I started this thread is to ask about modifications that could be done to deal with the #2 and 3 rod bearing failure. Considering that the car will see track I would like to do some homework. Have seen many threads about his topic and the brief summary is:
1) Cross or perpendicular drilling of the crank will not help much to deal with this issue, so I am not doing it; Disagree Stongly with this statement
2) Will do micro polish of the crank when installing new bearings;
3) The clearance of the rod bearings is important and it is advisable to have little bit bigger clearance on #2 (.003" (minimum) clearance on #2), but as I will use STD Glyco bearings, I do not have any room to play, as they all come in one size.You may want to use Plastigage to determine what your clearance actually is or is not.
4) Reduction of the oil foaming is important – will use appropriate oil (Millers 10w50 or 10w60 race oil). Viscosity and additives are important5) Will install Teflon crank scraper that I got from Paragon Products. The car already has updated oil pan baffle with OEM “crank scraper” that should also help little bit against oil foaming.
6) Keeping oil temperature down on track is important to retain higher viscosity of the oil, so I will put additional oil cooler in the area of front fender.
7) Will not use oil pan baffle, as don’t see how that would help me on 16 inch semi slick tires.What does tire width have to do with being able to pick up oil in a long sweeper?
8) Putting other harder rod bearings (good mod, but I will not do it). You would need to modify the rods, but in case anything isn’t right, you would have greater risk of losing your crank.
9) Coating the bearings. why? They are being coated with oil. Any coating you put on them reduces clearance
10) Will install the oil pick-up tube extension ring to reduce risk of sucking in air. Er?
11) Maybe will relocate the oil return line so that it is not right next to the pick-up tube, but this might create some other issues, so still debating about that.
12) Will add so called “windage ports” to reduce some oil foaming, but this mod is lees related to the #2 rad bearing issue.. windage ports between 1/2 cylinders and 3/4 cylinders, they allow the air displaced by the pistons somewhere to go instead of through the oil, significantly reducing foaming of the oil..
13) Try to not rew the engine above 6000 rpm – hard to do on a track when you try to set personal best lap Use stronger valve springs to keep them from floating, Jon Milledge makes a race cam and has a set of valve springs that go with them
I have seen tests related to the #2 rod bearing issues where results showed that 50% of oil is supplied to #1 rod, 25% to #4 and the remaining part is split between #2 and #3 (#2 seemingly receiving smallest part of those remaining 25%). To deal with it, some 944 and 928 engine builders have suggested the following:
Drilling #3 main and sending that oil to #2 and #3 rod will help. You need to modify the #3 main bearing to provide an oil path, if this is done. It can be full grooved, but will work better if it looks like the "other bearings".
Has anyone ever heard of this mod and if yes, I would appreciate any tips or pictures how this mod should be properly performed.
Other suggestions are welcomed.
Some information about my car and its planned application.
I am in a middle my 87 951 engine refresh/rebuild. The car originally was delivered to customer only in November 88 in Switzerland. I purchased in end of 2013 with 140k miles on it. The car is/will be driven in weekends and will see track day 5 – 6 time each year. It already has some suspension modifications, but it will not be a track car.
Some details about the engine/car:
It will have standard 2.5 block and head. I will put on rebuilt and modified k26/6 running 1.1 to 1.2 bar with VEMS and Siemens DEKA 630cc injectors. The car has full 3 inch DP and cat less exhaust with Magnaflow resonators. I will also use APR head studs, Wossner rods, new seals top and bottom, valve springs and some other parts, including KEP Stage 1 PP and Sachs HD clutch disk.
The cylinder walls look fine (although not ideal), the crank also does not have any scratches, the #2 bearing shows some usage signs the same as #1 main bearing.
The reason I started this thread is to ask about modifications that could be done to deal with the #2 and 3 rod bearing failure. Considering that the car will see track I would like to do some homework. Have seen many threads about his topic and the brief summary is:
1) Cross or perpendicular drilling of the crank will not help much to deal with this issue, so I am not doing it; Disagree Stongly with this statement
2) Will do micro polish of the crank when installing new bearings;
3) The clearance of the rod bearings is important and it is advisable to have little bit bigger clearance on #2 (.003" (minimum) clearance on #2), but as I will use STD Glyco bearings, I do not have any room to play, as they all come in one size.You may want to use Plastigage to determine what your clearance actually is or is not.
4) Reduction of the oil foaming is important – will use appropriate oil (Millers 10w50 or 10w60 race oil). Viscosity and additives are important5) Will install Teflon crank scraper that I got from Paragon Products. The car already has updated oil pan baffle with OEM “crank scraper” that should also help little bit against oil foaming.
6) Keeping oil temperature down on track is important to retain higher viscosity of the oil, so I will put additional oil cooler in the area of front fender.
7) Will not use oil pan baffle, as don’t see how that would help me on 16 inch semi slick tires.What does tire width have to do with being able to pick up oil in a long sweeper?
8) Putting other harder rod bearings (good mod, but I will not do it). You would need to modify the rods, but in case anything isn’t right, you would have greater risk of losing your crank.
9) Coating the bearings. why? They are being coated with oil. Any coating you put on them reduces clearance
10) Will install the oil pick-up tube extension ring to reduce risk of sucking in air. Er?
11) Maybe will relocate the oil return line so that it is not right next to the pick-up tube, but this might create some other issues, so still debating about that.
12) Will add so called “windage ports” to reduce some oil foaming, but this mod is lees related to the #2 rad bearing issue.. windage ports between 1/2 cylinders and 3/4 cylinders, they allow the air displaced by the pistons somewhere to go instead of through the oil, significantly reducing foaming of the oil..
13) Try to not rew the engine above 6000 rpm – hard to do on a track when you try to set personal best lap Use stronger valve springs to keep them from floating, Jon Milledge makes a race cam and has a set of valve springs that go with them
I have seen tests related to the #2 rod bearing issues where results showed that 50% of oil is supplied to #1 rod, 25% to #4 and the remaining part is split between #2 and #3 (#2 seemingly receiving smallest part of those remaining 25%). To deal with it, some 944 and 928 engine builders have suggested the following:
Drilling #3 main and sending that oil to #2 and #3 rod will help. You need to modify the #3 main bearing to provide an oil path, if this is done. It can be full grooved, but will work better if it looks like the "other bearings".
Has anyone ever heard of this mod and if yes, I would appreciate any tips or pictures how this mod should be properly performed.
Other suggestions are welcomed.
03-21-2016, 04:23 PM
#14
Rennlist Member
Run good oil and change it often .
Not meaning to be rude but i dont see any point in your modification . Your car has above 140k miles before you opened the engine.
Yet you intend to only track the car for 6 times a year. If this was a track car only i would understand but i think your money can be better spent elsewere . Are you going to be running Huge tires 285++ on all 4 corners . Are you a semi pro racer ? How did any of these cars last way past 120miles ie 200 000km on the stock bearings with out failures ? Truth is that most people dont have that issue and never will in a street car. Like most things "issues" gets hyped up on forums .
Have i changed rod bearings = sure when the oil pick up tube broke. Did the bearing have any wear after 26 years of use and abuse? only slight with 126k miles on odo and beaten for the passed 2 years .
When my piston rings gave in after 28 years i had to open it again , again after trackdays and hours on woot at autobahn but no wear on bearing n.2 . I am not a pro driver my tires are small 255 in back and i corner as hard as the car will let me on track but for me my engine seemed very reliable after 20+ years .
For serious racers or people who want a fix easy. $$$$ Drysump, that rod trick or maybe offset grind . How many offset grind engines have had bearing failures yet?
How many people like me with a weekend,daily 951 had bearing issues with the stock 2.5l engine in % maybe 0.5
Not meaning to be rude but i dont see any point in your modification . Your car has above 140k miles before you opened the engine.
Yet you intend to only track the car for 6 times a year. If this was a track car only i would understand but i think your money can be better spent elsewere . Are you going to be running Huge tires 285++ on all 4 corners . Are you a semi pro racer ? How did any of these cars last way past 120miles ie 200 000km on the stock bearings with out failures ? Truth is that most people dont have that issue and never will in a street car. Like most things "issues" gets hyped up on forums .
Have i changed rod bearings = sure when the oil pick up tube broke. Did the bearing have any wear after 26 years of use and abuse? only slight with 126k miles on odo and beaten for the passed 2 years .
When my piston rings gave in after 28 years i had to open it again , again after trackdays and hours on woot at autobahn but no wear on bearing n.2 . I am not a pro driver my tires are small 255 in back and i corner as hard as the car will let me on track but for me my engine seemed very reliable after 20+ years .
For serious racers or people who want a fix easy. $$$$ Drysump, that rod trick or maybe offset grind . How many offset grind engines have had bearing failures yet?
How many people like me with a weekend,daily 951 had bearing issues with the stock 2.5l engine in % maybe 0.5
03-21-2016, 06:00 PM
#15
Thanks, Bob. Your comments are welcomed.
Have seen posts of some experienced Porsche engine builders that cross of perp drilling will provide no benefit for 944 engines, if you do not rev it above 6500 rpm. I am not planning to do it as then I would need to go to solid lifters as the OEM ones are too soft/weak for any stronger springs. Might still do it – should be no big deal with the crank out of the engine. Would you suggest cross or perp drilling?
Regarding oil baffle – I will not see big G’s on corners thus thought that I have no need for oil baffle – when I look at the oil pan I cannot imagine that you could have oil starvation because of oil running to one side of the pan on a long corner, but I could be wrong.
Below is ling to the oil pick-up tube ring mod I was referring to. Its purpose is to lower the oil pick-up point to prevent any air going in to the pickup tube during cornering.
http://www.lindseyracing.com/LR/Parts/OILPANBKI.html
Have seen posts of some experienced Porsche engine builders that cross of perp drilling will provide no benefit for 944 engines, if you do not rev it above 6500 rpm. I am not planning to do it as then I would need to go to solid lifters as the OEM ones are too soft/weak for any stronger springs. Might still do it – should be no big deal with the crank out of the engine. Would you suggest cross or perp drilling?
Regarding oil baffle – I will not see big G’s on corners thus thought that I have no need for oil baffle – when I look at the oil pan I cannot imagine that you could have oil starvation because of oil running to one side of the pan on a long corner, but I could be wrong.
Below is ling to the oil pick-up tube ring mod I was referring to. Its purpose is to lower the oil pick-up point to prevent any air going in to the pickup tube during cornering.
http://www.lindseyracing.com/LR/Parts/OILPANBKI.html