952g63t
10+ Year Contributor
- 401
- 34
- Mar 19, 2012
-
Summit Point,
West_Virginia
Alright, this post might end up stirring up some mixed opinions but that's sort of the point. I have recently been doing some research on the 7-bolt oil system and of course indirectly crank-walk. Now before anyone gets too worked up, this isn't to dispute one cause over another or one fix/modification over another. This is just my contribution with my (albeit limited) experience on the subject and what I will be doing to my block to reduce the chances of it happening while improving the overall efficiency of the oiling system itself. I am rebuilding due to a failed rod bearing, not crank-walk. So, this will also help me to keep my thought process organized during my modifications. Also, it should be understood that (for the most part) all engines can suffer from crank-walk and that to some extent it has been made out to be more common than it actually is. Not everyone with a 7-bolt has suffered crank-walk and these failures are not limited to manual transmissions, but are just statistically more common in them. PLEASE NOTE: Of course many choose to perform the engine swap and use the early model 4g63 6-bolt design (I believe these were used from 90-4/92) while it's a tried and true option, this is meant to help those looking to continue using the 7-bolt platform.
First things first, lets start off with the basics. It's all relatively understood that the manual 7-bolts suffer a higher than average wear rate of the thrust bearing surface due to a number of proven and speculated causes. All of which vary from one application to the next. But primarily being caused from a lack of lubrication between the crank thrust bearing journal and the bearing itself. I feel that the cause of this lack of oil is what is mostly disputed, not that its happening at all. So lets list the major/common ones.
These are the main reasons that stood out in my research, feel free to suggest something to add to the list. This list is intentionally general. I don't feel that detailing specific causes will do much in terms of providing useful information because there are too many variables that are involved. The point of this is not to point the finger at any one possible cause and say that is the root of the issue but to organize it in a manner where oil system modifications that address basic failure points is outlined in one place.
#1. Low oil pressure &/or volume directly or indirectly caused be any oil system variables &/or failures, age, poor maintenance, excessive wear, out of spec tolerances, etc...
#2. Improper installation of directly or indirectly related parts (OEM or aftermarket)
#3. Defects in parts manufacturing process (OEM or aftermarket)
#4. Poor engine oil system engineering &/or design from Mitsubishi
#5. Faulty drive train/transmission functions
#6. General failure caused by any application outside of the engines scope of originally engineered capabilities
In addition to standard machining and assembly practices, these are some of the most common modifications that have been previously discussed and recommended to help mitigate the issue thanks in large by the hard work and dedication of many DSM enthusiasts before me. I will add more details and references later.
#1. Oil squirter delete/modification
#2. Crankshaft/connecting rod modification
#3. Thrust bearing modification
#4. Main girdle modification
#5. Disabling the clutch switch
#6. ?
I will be performing some of these modifications myself and some additional ones that maybe some of you have never heard of. Most notably I will be addressing oil pressure and volume to the thrust bearing by replacing my oil squirters with new (thoroughly cleaned and lubricated) OEM's, completing a OEM BSE and replacing the front case/oil pump and OFH, also with new OEM's. I may do some casting work and will at least be smoothing out rough oil return/channel surfaces. I will also be addressing drive line vibrations/harmonics and alignment issues by upgrading all of the mount bushings, replacing the hardware, and upgrading the harmonic damper.
Some lesser common fixes I will be implementing and sharing my experience in doing will include:
#1. Adding additional dampening. Specifically increasing the shock dampening of the drive line/transmission by installing at least one engine shock as linearly close to the rear M8x6 "crank-walk bolt" location as possible. My main goal here is to add additional shock load protection for the trans/engine during operation.
#2. Because I will be doing a complete BSE and creating a higher than "normal" running oil pressure, rather than porting my OFH I will be tapping & adding 1 additional 1g style oil squirter to the front balance shaft bearing oil feed hole location. Specially, to provide additional oiling to the thrust bearing surfaces. I have only mocked this up in my head so far, so if a clearance issue exists I will be working around as much as possible. I believe I can flip the squirter so that its facing/pointing towards the thrust bearing while staying clear of the rotating assembly. We'll see.
Personally, I feel that crank-walk is caused by any and all of the factors stated in any combination thereof. I'm sure there are more, but I need to get off here to take care of some things. I will be adding more to this as time goes on.
As always, thanks for the input.
First things first, lets start off with the basics. It's all relatively understood that the manual 7-bolts suffer a higher than average wear rate of the thrust bearing surface due to a number of proven and speculated causes. All of which vary from one application to the next. But primarily being caused from a lack of lubrication between the crank thrust bearing journal and the bearing itself. I feel that the cause of this lack of oil is what is mostly disputed, not that its happening at all. So lets list the major/common ones.
These are the main reasons that stood out in my research, feel free to suggest something to add to the list. This list is intentionally general. I don't feel that detailing specific causes will do much in terms of providing useful information because there are too many variables that are involved. The point of this is not to point the finger at any one possible cause and say that is the root of the issue but to organize it in a manner where oil system modifications that address basic failure points is outlined in one place.
#1. Low oil pressure &/or volume directly or indirectly caused be any oil system variables &/or failures, age, poor maintenance, excessive wear, out of spec tolerances, etc...
#2. Improper installation of directly or indirectly related parts (OEM or aftermarket)
#3. Defects in parts manufacturing process (OEM or aftermarket)
#4. Poor engine oil system engineering &/or design from Mitsubishi
#5. Faulty drive train/transmission functions
#6. General failure caused by any application outside of the engines scope of originally engineered capabilities
In addition to standard machining and assembly practices, these are some of the most common modifications that have been previously discussed and recommended to help mitigate the issue thanks in large by the hard work and dedication of many DSM enthusiasts before me. I will add more details and references later.
#1. Oil squirter delete/modification
#2. Crankshaft/connecting rod modification
#3. Thrust bearing modification
#4. Main girdle modification
#5. Disabling the clutch switch
#6. ?
I will be performing some of these modifications myself and some additional ones that maybe some of you have never heard of. Most notably I will be addressing oil pressure and volume to the thrust bearing by replacing my oil squirters with new (thoroughly cleaned and lubricated) OEM's, completing a OEM BSE and replacing the front case/oil pump and OFH, also with new OEM's. I may do some casting work and will at least be smoothing out rough oil return/channel surfaces. I will also be addressing drive line vibrations/harmonics and alignment issues by upgrading all of the mount bushings, replacing the hardware, and upgrading the harmonic damper.
Some lesser common fixes I will be implementing and sharing my experience in doing will include:
#1. Adding additional dampening. Specifically increasing the shock dampening of the drive line/transmission by installing at least one engine shock as linearly close to the rear M8x6 "crank-walk bolt" location as possible. My main goal here is to add additional shock load protection for the trans/engine during operation.
#2. Because I will be doing a complete BSE and creating a higher than "normal" running oil pressure, rather than porting my OFH I will be tapping & adding 1 additional 1g style oil squirter to the front balance shaft bearing oil feed hole location. Specially, to provide additional oiling to the thrust bearing surfaces. I have only mocked this up in my head so far, so if a clearance issue exists I will be working around as much as possible. I believe I can flip the squirter so that its facing/pointing towards the thrust bearing while staying clear of the rotating assembly. We'll see.
Personally, I feel that crank-walk is caused by any and all of the factors stated in any combination thereof. I'm sure there are more, but I need to get off here to take care of some things. I will be adding more to this as time goes on.
As always, thanks for the input.
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