Can this M96 crankshaft be saved?
07-13-2014, 12:33 AM
#1
Drifting
Thread Starter
Can this M96 crankshaft be saved?
The local Porsche Indy was convinced the problem was IMS -even when I told him it had just been replaced about 2000miles earlier(LN). I walked-quickly!
Anyway here's what was causing the noise.The #5 journal is scored-see pic. Obviously the bearing shells have even more damage but are they did not disintegrate. Strangely the bearing shells appear to have rotated in the con rod big end because they are scored on both sides. The scoring fails the crude fingernail test. I'm sure the machine shop will want to 'try' to save the crankshaft. On a regular engine I would take a chance but the M96 rebuild and re-install is a daunting & expensive task if it turns out to be futile.
For that reason, I would be very grateful for advice on how to proceed with this project and what to ask a machinist.
For background, the engine has 90k miles, several upgrades (LN filter mod,new IMS to name a few) oil was very clean.No signs of any dirt inside the engine,no sludge and obviously had not been opened since new except for the minor IMS bearing job.
Only two other defects found so far -one chain ramp is pitted but nothing severe. 22 of the lifters had jammed solid ! Overall ,the engine is in remarkably good condition - except for #5 con rod bearing and the lifters.
Anyway here's what was causing the noise.The #5 journal is scored-see pic. Obviously the bearing shells have even more damage but are they did not disintegrate. Strangely the bearing shells appear to have rotated in the con rod big end because they are scored on both sides. The scoring fails the crude fingernail test. I'm sure the machine shop will want to 'try' to save the crankshaft. On a regular engine I would take a chance but the M96 rebuild and re-install is a daunting & expensive task if it turns out to be futile.
For that reason, I would be very grateful for advice on how to proceed with this project and what to ask a machinist.
For background, the engine has 90k miles, several upgrades (LN filter mod,new IMS to name a few) oil was very clean.No signs of any dirt inside the engine,no sludge and obviously had not been opened since new except for the minor IMS bearing job.
Only two other defects found so far -one chain ramp is pitted but nothing severe. 22 of the lifters had jammed solid ! Overall ,the engine is in remarkably good condition - except for #5 con rod bearing and the lifters.
Last edited by Schnell Gelb; 02-15-2015 at 11:21 PM.
07-13-2014, 01:04 PM
#3
Race Director
The subject of crankshaft resurrection has come up before and without doing a search to confirm my memory I do not think it is a recommended course of action.
Oversize bearings are not available -- this was circa 2011/2012 and maybe (maybe) this has changed -- so the crank pin or main bearing can't be ground undersized to clean it up -- assuming this wouldn't compromise the surface hardening/heat treatment -- and building up the worn crank pins or mains with say an application of hard chroming and regrinding to stock size has not proved to be successful either.
Other crank main/pin bearing build up/restoration techniques such as welding are likewise not advised.
I seem to recall the above was courtesy of Jake Raby in response to a posting by someone else, while I was the one who offered up the hard chrome suggestion as in the machine shop many a worn bearing journal was repaired with a proper hard chrome application then regrinding to size, but Jake R. shot this down as I recall.
However, you can check ads in Excellence and Panorama for shops specializing in engine rebuilds/repairs and learn if any offer crankshaft rebuilding services. Things may have changed.
You can even check with Jake Raby but I seem to recall he does not sell parts only complete rebuilt engines. But check anyhow. Maybe he knows someone that rebuilds cranks for these engines.
Oversize bearings are not available -- this was circa 2011/2012 and maybe (maybe) this has changed -- so the crank pin or main bearing can't be ground undersized to clean it up -- assuming this wouldn't compromise the surface hardening/heat treatment -- and building up the worn crank pins or mains with say an application of hard chroming and regrinding to stock size has not proved to be successful either.
Other crank main/pin bearing build up/restoration techniques such as welding are likewise not advised.
I seem to recall the above was courtesy of Jake Raby in response to a posting by someone else, while I was the one who offered up the hard chrome suggestion as in the machine shop many a worn bearing journal was repaired with a proper hard chrome application then regrinding to size, but Jake R. shot this down as I recall.
However, you can check ads in Excellence and Panorama for shops specializing in engine rebuilds/repairs and learn if any offer crankshaft rebuilding services. Things may have changed.
You can even check with Jake Raby but I seem to recall he does not sell parts only complete rebuilt engines. But check anyhow. Maybe he knows someone that rebuilds cranks for these engines.
07-13-2014, 05:16 PM
#4
Drifting
Thread Starter
Thank you both for the wisdom. I had thought of asking John Edwards at Costa Mesa R&D. He has a good reputation for honesty & competence on the air-cooled engines .
I'll inform the Forum of the outcome because good used crankshafts are hard+expensive($800+ -) to find.
I'll inform the Forum of the outcome because good used crankshafts are hard+expensive($800+ -) to find.
07-13-2014, 06:46 PM
#5
Race Director
Thank you both for the wisdom. I had thought of asking John Edwards at Costa Mesa R&D. He has a good reputation for honesty & competence on the air-cooled engines .
I'll inform the Forum of the outcome because good used crankshafts are hard+expensive($800+ -) to find.
I'll inform the Forum of the outcome because good used crankshafts are hard+expensive($800+ -) to find.
Here's a link the thread:
https://rennlist.com/forums/996-foru...aft-specs.html
The "acracer" post I referred to above is #8. You might send him an email and ask him about the crankshaft.
07-13-2014, 07:06 PM
#6
Drifting
Thread Starter
Interesting link-that is helpful.Thank you.
I'll call Gleason and ask who has their machines nearby. http://www.gleasonengineering.com/
I note one celebrated contributor advises crack testing because 50% of cranks he inspects are cracked. Wow! that is a horrific statistic.
I'll call Gleason and ask who has their machines nearby. http://www.gleasonengineering.com/
I note one celebrated contributor advises crack testing because 50% of cranks he inspects are cracked. Wow! that is a horrific statistic.
07-14-2014, 12:04 AM
#7
Drifting
In post #9 he states
or am I missing something? 
Or maybe you figure that he found the 996 specs and didn't post?
Originally Posted by Aracer
OOP'S THAT'S FOR THE 964 ENGINE....WILL GIVE EVERYONE THE SPECS FOR 996 LATER
Or maybe you figure that he found the 996 specs and didn't post?
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07-14-2014, 11:56 AM
#8
Race Director
The crank dimensions I knew were no good for as you pointed out in the following post acracer said the dimensions were for a 964 crank.
AFAIK, and I've kept my eye out for them, there have not been any 996 crankshaft dimensions published. I put out some feelers to see if I could get some from my tech contacts but the info was not right at hand -- the info was supplied -- if it was supplied at all and I'm not sure it was or won't be sure until I actually see it -- almost prior to the 996 launch and this info tends to settle to the bottom of the sizable stack of printed material a tech ends up with over the years -- and did not pursue it. Were I seriously considering rebuilding a 996 (or in my case a 986) engine I might feel more driven to get my hands on this info but I'm not in the engine rebuilding mode and so I didn't push the techs for this.
07-14-2014, 12:07 PM
#9
Drifting
Thread Starter
Macaster, relax, you've already done more than your share to help Rennlisters !
The older the M96 engined cars get ,the more often this subject will come up.The less satisfactory the solution to fundamental problems like cranks, blocks etc - the lower the value of the cars. The honest contributions of experts who explain on this Forum that 50% of the crankshafts that come in have cracks, the worse it gets.
We may love these cars but if they don't run -what value do they have? We have seen this happen to cars like the 928, Jaguar XJS. Arguably ,the parts/repair situation for their engines is stronger than for the M96 cars. So I suggest it is in our collective interest to pool resources here to save the cars.In the case of the XJS -it was saved by Forums like this - particularly Jag-Lovers.. We could do the same.I'll make a minor contribution by posting here the outcome of the crankshaft saving attempt.
The older the M96 engined cars get ,the more often this subject will come up.The less satisfactory the solution to fundamental problems like cranks, blocks etc - the lower the value of the cars. The honest contributions of experts who explain on this Forum that 50% of the crankshafts that come in have cracks, the worse it gets.
We may love these cars but if they don't run -what value do they have? We have seen this happen to cars like the 928, Jaguar XJS. Arguably ,the parts/repair situation for their engines is stronger than for the M96 cars. So I suggest it is in our collective interest to pool resources here to save the cars.In the case of the XJS -it was saved by Forums like this - particularly Jag-Lovers.. We could do the same.I'll make a minor contribution by posting here the outcome of the crankshaft saving attempt.
07-14-2014, 03:39 PM
#10
Former Vendor
First things first, have the crank magna flux tested for cracks. If it passes then worry about restoring the journal. If it does not, then journal restoration doesn't matter. Cranks with spun bearings generally crack during the failure.
I have developed a means of journal restoration, but it requires many processes and an altered bearing to be used. After all those efforts are done the crank must be Ion Nitrided to restore surface hardness, as the factory hardness only penetrates .003" into the crankshaft.
You will not find the M96 crank dimensions posted anywhere.
I have developed a means of journal restoration, but it requires many processes and an altered bearing to be used. After all those efforts are done the crank must be Ion Nitrided to restore surface hardness, as the factory hardness only penetrates .003" into the crankshaft.
You will not find the M96 crank dimensions posted anywhere.
07-14-2014, 04:09 PM
#11
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I had my crank welded and re grinded when my 5th rod bearing went bad.
I had to change the rod allso. I found used from England, I think it was 100£ shipped.
Driven over 50k km's after that. I allso had cyliders that were too much out of round. (supposedly)
At 10k km oil change interval, no need to add oil. Oil level drops one notch in the dash gauge.
No fouled plugs etc....
I allso ported my cylinder heads and used wet sandpaper to clean the aluminium debries from cyl 5
Still running strong
I had to change the rod allso. I found used from England, I think it was 100£ shipped.
Driven over 50k km's after that. I allso had cyliders that were too much out of round. (supposedly)
At 10k km oil change interval, no need to add oil. Oil level drops one notch in the dash gauge.
No fouled plugs etc....
I allso ported my cylinder heads and used wet sandpaper to clean the aluminium debries from cyl 5
Still running strong
07-14-2014, 04:28 PM
#12
Drifting
Thread Starter
Speed in Finland,
Kiitos paljon !
So yours failed on number 5 also-interesting. I wonder why number 5 ?
Congratulations on your repair.It is encouraging to read that someone tried a risky repair and succeeded.I carefully follow the comments of Jake Raby above & I wrote "I note one celebrated contributor advises crack testing because 50% of cranks he inspects are cracked. Wow! that is a horrific statistic."
Kiitos paljon !
So yours failed on number 5 also-interesting. I wonder why number 5 ?
Congratulations on your repair.It is encouraging to read that someone tried a risky repair and succeeded.I carefully follow the comments of Jake Raby above & I wrote "I note one celebrated contributor advises crack testing because 50% of cranks he inspects are cracked. Wow! that is a horrific statistic."
07-14-2014, 04:44 PM
#13
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Your welcome, ole hyvä
When I took my engine apart I found no solid proof why the bearing failed. Failure started from mainbearing, and the debries from that took out the rodbearing
My theory was, that engine had oil starvation on nurburgring. I didn't have the oil filled up to max and it's possible the the failure began there. Drove about 4k km after the road trip, before the bearing went.
Other theory was that allmost all the oiljets, that are in the crank cradel, was stuck open.
This might cause poor oil pressure on the crank when engine is hot and idling.
If I remember right, logray found allso stuck oiljets in his engine when he did 3,6 conversion.
When I took my engine apart I found no solid proof why the bearing failed. Failure started from mainbearing, and the debries from that took out the rodbearing
My theory was, that engine had oil starvation on nurburgring. I didn't have the oil filled up to max and it's possible the the failure began there. Drove about 4k km after the road trip, before the bearing went.
Other theory was that allmost all the oiljets, that are in the crank cradel, was stuck open.
This might cause poor oil pressure on the crank when engine is hot and idling.
If I remember right, logray found allso stuck oiljets in his engine when he did 3,6 conversion.
07-14-2014, 04:50 PM
#14
Drifting
Thread Starter
Stuck oil jets -Hmmmm, thanks I'll test them too.
At least you had the fun of a run around the 'ring before yours died.Mine was not so exciting !
One mod I plan on doing to mine(if I can save the engine) is the oil/water heat exchanger delete. Apparently that increases oil pressure somewhat.Yes, I know there are lots of other mods to do but that seems to be one that is often misunderstood.
Interesting to note since you are from Finland that many of the Boxsters were made by Valmet in Finland -along with the Saabs and tractors ! An interesting company.
At least you had the fun of a run around the 'ring before yours died.Mine was not so exciting !
One mod I plan on doing to mine(if I can save the engine) is the oil/water heat exchanger delete. Apparently that increases oil pressure somewhat.Yes, I know there are lots of other mods to do but that seems to be one that is often misunderstood.
Interesting to note since you are from Finland that many of the Boxsters were made by Valmet in Finland -along with the Saabs and tractors ! An interesting company.
07-14-2014, 10:04 PM
#15
Race Director
Stuck oil jets -Hmmmm, thanks I'll test them too.
At least you had the fun of a run around the 'ring before yours died.Mine was not so exciting !
One mod I plan on doing to mine(if I can save the engine) is the oil/water heat exchanger delete. Apparently that increases oil pressure somewhat.Yes, I know there are lots of other mods to do but that seems to be one that is often misunderstood.
Interesting to note since you are from Finland that many of the Boxsters were made by Valmet in Finland -along with the Saabs and tractors ! An interesting company.
At least you had the fun of a run around the 'ring before yours died.Mine was not so exciting !
One mod I plan on doing to mine(if I can save the engine) is the oil/water heat exchanger delete. Apparently that increases oil pressure somewhat.Yes, I know there are lots of other mods to do but that seems to be one that is often misunderstood.
Interesting to note since you are from Finland that many of the Boxsters were made by Valmet in Finland -along with the Saabs and tractors ! An interesting company.
Remember the oil is in contact with the hottest parts of the engine and plays an important cooling function.
What you gain in oil pressure with the removal of the oil/water heat exchanger you'll like lose and then some when the oil gets much hotter than it would otherwise.