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7-Bolt Oil System Modifications

Does your 7-bolt have any anti-crank-walk modifications?

  • Yes, and still suffered a related failure.

    Votes: 0 0.0%
  • No, and still suffered a related failure.

    Votes: 0 0.0%

  • Total voters
    18

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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.
 
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I'm scratching my head on fix #2 and how that's going to help anything...
Mains oil pressure and crank rotation building a hydrodynamic wedge is what keeps the crank thrust surface off the bearing in both laterally loaded and unloaded situations. Throwing unpressurized, free-floating oil at the crank from afar will instead be quite the lesson in futility, would it not? You've probably got as much splashing around in there from all the movement of the crankshaft lobes and rods themselves.
 
I'm scratching my head on fix #2 and how that's going to help anything...
Mains oil pressure and crank rotation building a hydrodynamic wedge is what keeps the crank thrust surface off the bearing in both laterally loaded and unloaded situations. Throwing unpressurized, free-floating oil at the crank from afar will instead be quite the lesson in futility, would it not? You've probably got as much splashing around in there from all the movement of the crankshaft lobes and rods themselves.

Interesting point, I never really thought there was that much oil being sloshed around inside the case. The way I imagine it, aside from the oil jets most of the oil is draining back down the crank case surfaces. Mostly from the crank main bearing cap sections. I don't think it would be futile, maybe not as effective as actually having more oil protection being fed directly to the thrust surfaces but how would you pull that off without some major machine work?

Any additional oil on that bearing surface has to be an improvement though, no?

Thanks for the input sordid.
 
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It isnt going to do anything. Try squiring water onto a spinning fan. Anything that touches the blades will instantly be slung off by inertia. A smarter move would be to remove the squirters completely to increase pressures to the mains. There is a reason why everybody removes them.
 
+1
You would probably see a decrease in performance because of the additional oil being winded up in the crankcase. There's a reason windage trays and crank scrapers are installed.
 
It isnt going to do anything. Try squiring water onto a spinning fan. Anything that touches the blades will instantly be slung off by inertia. A smarter move would be to remove the squirters completely to increase pressures to the mains. There is a reason why everybody removes them.
+1
You would probably see a decrease in performance because of the additional oil being winded up in the crankcase. There's a reason windage trays and crank scrapers are installed.

I am not sure if you guys understand what I am saying, the oil jet is aimed directly between the counterweight and the cap. Even if a little bit of oil was splashing onto the counterweight the effect would be infinitesimal. There's almost 1/2" of a gap there. The jet reach is maybe 3"? We're talking about (1) tiny little oil jet squirter here. For the most part it would be completely missing the counterweight. The scraper will still be able to perform its intended function.
 
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I dont think you understand how it works. Picture this:

Spinning crank. Oil escaping from bearing clearances at high pressures. Centrifugal force pushing oil out.

Now tell me how splashing a little bit of oil is going to overcome the oil pressure leaving the journals and it being slung around at a couple thousand rpms. Simply put its not. Just like my spraying oil on a moving fan analogy. It isnt going to creep into anywhere important before it is slung off.
 
No a oil squirter will not help the thrust bearing crank walk is a goofy subject. Because most people that talk about it have never experienced it.they just read. Basically it occurs from a engine poorly maintained and mistreated or a engine that has seen sever service action. period. Picture this. The crank floats in the mains on a thin stream of oil now the engine and trans are bolted together they will never move apart now u press the clutch the fork moves and u are applying lateral force the the crank shaft thru the clutch and fly wheel. Where does the crank go? Remember it's floating. It's forced out the front of the oil pump. Ur thrust bearing retains the crank from moving out of the block. It's safe guard is the oil that is supplied to the bearing this creeps thru the clearances and down the filet to the thrust surface. Now poor oil quality or a lack of a high clutch pressure rate. Worn bearings out of service time and a life time of beating on. Trust me. U would want to walk out to this is why u see more wear to the thrust on the back side facing 4 than front facing 2. The clutch is pushing the crank out of the block. Tell tell signs are oil leaks on the front crank seal and rear main. As the crank walks it pushes small amounts of oil past the seal. The way to safe guard is good quality oil. Changed reg. If u must run a heavy clutch. Look into a multi disk. These don't use near the pressure become ur doubling or tripling the friction surface. Careful about oil pressure to little no good. Too much. No good u will kick bearings out too high is just as bad as no oil pressure clutch switch delete is a plus here with no oil on start up the crank is riding on the thrust face dry. Just like sex dry is no good taking away the clutch pressure on start up frees the crank and does not force it till pressurized oil is in the thrust clearance. This is why a squirter would not work here splashing oil on it will do nothing at all. The oil must come from inside the thrust face when it reaches the clearance the flow is greater than the rate it can leave. This creates pressure it's the pressure that forces the crank away from the thrust face. Evenly on both sides now add a clutch and the force is now uneven. Hope this helps. Not trying to shoot down ur idea. Just save u some time if u want to prevent it. Good clean oil and if ur gonna beat on it everyday of its life start saving now for a rebuild. Old racers tail. If u ain't breaking shit ur going too slow it's the nature of the beast. If it's too much then it's time for a new hobby trust me I've broke plenty of dsm stuff gotta pay to play
 
I dont think you understand how it works. Picture this:

Spinning crank. Oil escaping from bearing clearances at high pressures. Centrifugal force pushing oil out.

Now tell me how splashing a little bit of oil is going to overcome the oil pressure leaving the journals and it being slung around at a couple thousand rpms. Simply put its not. Just like my spraying oil on a moving fan analogy. It isnt going to creep into anywhere important before it is slung off.

This. Picture in your head how the oil flows through the enngine. It comes out of the hole in the main journal, lubricates the main bearing then escapes outward; rapidly. Spraying additional oil there will do nothing more than create windage problems.

It's good that you're thinking outside the box but this isn't a viable solution. There's a ton of oil supply to the thrust face. The problem is almost always abuse or mistreatment.
 
Ah, meant to add multiple disk clutch to my list....

Ok, I concede.

I still don't see how oil and water are even remotely close in characteristics, and how oil is shooting out from the thrust fillet at a rate in which supplemental oil would be completely deflected. But then again, I am also very stubborn. ;)

Thanks for the input, much appreciated.
 
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Dang... I feel left out. I've posted many threads about crank-walk... they don't seem to be mentioned here. When I started this journey about 10 years ago I posted a list like 952g63t, but my list was much different. I do not think spraying oil at the thrust washer, will resolve much. Mitsu took alot of weight out of the lower end of the 7 bolt (compared to the 6 bolt) plus the increased the stiffness with the girdle. Those who have taken a vibrations course might have perked their interest in hearing "mass" and "stiffness" in the same sentence... yes I think it is a natural frequency, or modal issue. I have no proof of this other than engine blocks have many modes of vibration. If an axial mode of the block-girdle line up with an axial or bending mode of the crank... gobs of oil wont prevent breakdown of the oil film layer. The link below is a culmination of my work on crankwalk. In short, I added a second thrust washer.

http://www.dsmtuners.com/threads/crankwalk-fix-for-7bolt-others.453033/

In addition to the above summary here are a few previous threads

below (edited) is from the following link: http://www.dsmtuners.com/threads/du...-the-same-mistakes.202403/page-2#post-1700900

1. oil pressure before compression -no plugs -no spark, -no fuel.... spin it over.
2. align a 7 bolt girdle (or 6 bolt center main) in the axial direction.
4. disconnect your clutch switch for start up (no clutch load on thrust bearing)


below is from the link: http://www.dsmtuners.com/threads/re...have-caused-it-need-help.200076/#post-1683340

- Welded thrust surfaces are common place in the engine world. So is re-nitriding.
- Crankwalk is not unique to 7bolts nor DSMs.
- Most engine wear is on start up (no oil supply).
- 7 bolts have a problem with crankwalk, ever so on rebuild.
- Axial alignment of girdle is important
- You will get crankwalk advise from people who have never rebuilt a 7 bolt.
- Disconnect your "depress clutch to start" switch forever & start in neutral.
- get full oil pressure upon rebuild with NO spark & NO plugs (spin engine no compression, disconnect sensor at head).
- break in with normal oil then switch to synthetic (heavy).
- consider an external oil cooler.
- make sure your oil pump works.
- wait for my crankwalk experiment results (2nd thrust surface)
- Use normal bearings (clevite or DSM)
- Reworked cranks are sensitive to low tide, planetary line ups and other nonsense.
- Screwed-up reworked cranks are by definition.... screwed up.
- A fresh untouched crank is worth $100 for your piece of mind.

From a guy who has build a 200 mile crankwalker and a 2500 mile non crankwalker, working on a third with 2 thrust surfaces.

I could swear that I have posted many more... but this is what I found in a few minutes.
 
bjones18,

The whole thing about vibrations and alignment issues with the drivetrain, crank & girdle I feel is one of the primary design flaws which cause the premature thrust wear for the 7-bolts. It's hard to pin down because there are so many different possible causes that can exacerbate an already flawed design. Definitely in agreement with you on these factors. Come to think of it I actually thought about doing exactly what you did by adding a second thrust surface. Only, my idea was to mill out an exact dimensional copy of the existing thrust bearing location and add another replacement thrust bearing to the mix. Interested in finding out how well your fix held up.

Regarding my thoughts on supplying additional oil to the fillet, it was never meant to be an end all be all fix like your second thrust bearing idea. The way I figured it, that oil feed was already being blocked off for the BSE. Why not just utilize an existing oil feed location that was close enough to the bearing in question. Again, not a permanent fix so much as just a supplemental supply of oil for something that could use all the help it can get. :idontknow:

Some other interesting things I came across included a bad run of cranks from the factory during manufacturing. Supposedly the thrust journal on the cranks were being milled off angle, and with a less than ideal surface texture. This was purported to have come from a mitsu employee at some point in time when the service bulletin was issued to all the dealerships. It seems that many cases have been successfully addressed by replacing the crankshafts.
 
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primary thrust-oil-source is being squeezed out of the main bearing journals. Coining angle on the ends of the thrust bearings is key to convincing oil to enter the thrust sandwich. Putting a small chamfer on the edge of the main bearing can provide a "leak path" to feed the leading edge of the thrust bearing from the bearing journal. In any sense of the subject, keeping an oil film in this gap is either science, or black magic. Science says reduce the load, increase surface area, and increase viscosity.

Fix is working good. but recent job change, new house, and many other time consuming projects has this hobby in neutral till spring.
 
Another thing to consider is reworked cranks. Mitsubishi cranks are forged. And also layered like a oreo cookie the outside is a hard forged underneath that is a softer cream filling this takes up some of the harmonics of the engine . Then finally the middle back to hard forge. When a crank is turned the outer hard layer is taken away. Now u have the softer filling as a bearing face. I have seen these cranks walk more and also eat bearings on 100 mile rebuilds. For this reason i refuse to use a machined crank shaft. Not only that but the crankshaft is most likely twisted to some degree from its previous use. If a polish won't take the wear out It's best to just save time money and a lot of f bombs and replace it now taking up ur idea about the oil squirters. If u rly wanted to r &d look at options of taking oil pressuer from the deleted bs and have the block redrilled to divert oil from the upper main to holes on the upper and lower main thrust face on the back side of 3. This would effectively provide more oil pressure to the thrust itself from inside. Similar to the the #2 main feeds the #2rod thru the crank shaft u could have the crank machined to use as a oil passage but any other crank on rebuild would also need modified it's a idea would be far better but also costly and time consuming just an idea of mine. No real research to provide just a theory
 
I looked into this a lot when building my engine, here's the things i have done to help oiling:

-Went with a Revised NA 2.4 block, no squirters
-Ground casting roughness out of main oil galleries on side of block
-Enlarged head oil teardrop slightly (head had practically nothing milled out of it so didnt go very far)
-ARP main studs and cap alightment dowel kit (to make sure mains can never ever ever move)
-Stub shaft BS delete (less supported than a full length but less oiling too)
-Three piece crank scraper (to cut windage cloud, help with cooling of the rotating assembly, and reduce oil frothing)
-Fluidampr crank pulley
-Ported Oil filter housing to compensate for higher pressure from some of above mods (may need to do a bit more)

I am running Clevite street bearings. I think the things I have done, combined with the car being an automatic will basically eliminate crankwalk as a problem forever for me unless some unforseen bad thing happens.
 
I thought the main reason for crank walk is stuck open oil squirters which drops the oil pressure in the main galley which leads to low pressure to the main caps.

Porting the oil filter housing will do just this much, if you really want to lower the oil pressure then you have to cut a coil or two off of the OFH spring.

Both of my cars have 4g64 engines with no oil squirters which by default raises the oil pressure. I have ported the OFH which gave me these numbers:

Cold start :
idle - 60 - 65psi
1.5k - 75psi
accelerating to 3k - 90psi
cruise - 75 psi

Hot engine

idle - 25psi
cruise at 2.5k - 50psi
cruise at 3k - 60 psi
wot - 90-100 psi

With the OFH spring cut (1coil)

Cold start:

idle - 50psi
1.5k - 60psi

Hot engine:

idle - 15psi
cruise 3k - 50psi
wot - 75-80 psi

The gauge is Autometer fed from a 4an T from the OFH
 
The only way a "reworked", ground, undercut or machined crank will lead to a premature thrust failure is if it were machined out of spec. Just because it's a machined crank does not mean it's junk. It has to do with tolerances, not the hardening process. Mitsu cranks are induction hardened which provides a much deeper hardening than other methods and grinding a crank .010-.020" isn't enough to get to the "cream filling" LOL.

Also, "stuck" oil squirters don't cause low oil pressure. The valve in the squirter body is always open during engine operation and closes when the engine is shut down. The purpose of the valve is to prevent oil drainback and subsequent dry starts. For some reason a lot of people seem to think the squirters pulse in time and this means that a stuck valve will cause more oil leakage than normal. This is not the case.
 
The HLA pressure regulator does not change the oil feed path to the turbo compared to the OEM setup. It only reduces the pressure to the HLA's (lifters). The cams and turbo oil feed (it is off the exhaust cam gallery in a DSM head) are just directly joined to the head's main oil supply, just like the OEM distribution block does. You should not have to move the oil feed for your 16g anywhere at all with our HLA pressure regulator.
 
IMHO Jack's transmission has researched the subject so thoroughly they have an online article that discusses all the reasons why 7-bolts crank walk. So I would check them out before you do any mods to your oiling system. If you have trouble finding the article just put in DSM Crankwalk. That should take you right to it.
 
The HLA pressure regulator does not change the oil feed path to the turbo compared to the OEM setup. It only reduces the pressure to the HLA's (lifters). The cams and turbo oil feed (it is off the exhaust cam gallery in a DSM head) are just directly joined to the head's main oil supply, just like the OEM distribution block does. You should not have to move the oil feed for your 16g anywhere at all with our HLA pressure regulator.

Ok awesome! I've only seen simplified diagrams of the oiling system, I wasnt sure if it pertained to the whole head or not. That's awesome info to have. If anything, it should ensure that it gets the proper oil at all times. Perfect, that's on my must have list before I hit the track this year for sure.
 
Jafro has a great video on Dsm 6 bolt and 7 bolt oiling system and how things work with and without balancer shafts.
 
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