Why is a crankwalked block unusable? Whats the big deal?

[lee101315]

This was my post from another thread regarding crankwalk.




Fill me in on a couple of things, since I am rebuilding my crankwalked 7 bolt engine for my 95 GST.

Where is the irreversible damage to the block ? I could not find any on mine

Why would a slightly worn endplay bearing ruin the crank? Of course, my case was not a complete engine failure. The crank is made of a much stronger material than the bearing. I am not saying this is impossible, just very unlikely.

Why is my motor being taken apart? I spun the rod bearings twice in 4 months( I changed the con bearings with the engine in the car the first time since I was in desparate need of transportion the following week). I discovered the excessive end play when the motor was dismantled.

I did not have any problems with clutch engagement.
I did not wear out my crank sensor.

How did I repair it? I sent out the crank to get the second and third rod bearing journal repaired( back to STD size, yes, I know a GREAT engine machinist), while polishing the crank. I called the mitsu dealer to get the proper main bearings (with the Vin of course)
and thats it.

I expect this engine to last several years, this was not just a "patch".

Maybe in some cases, the end play bearing actually breaks?

Although I am new to DSMs, I am certainly not new to engines, and I run a shop that specializes in Porsche, Mercedes, and BMW( I learned the hard way that german cars have a poor $$$ to performance ratio )

How many people on this forum toss that term "crankwalk" around and dont have any real knowledge on it? Its been going on for decades. The old VW bugs "crankwalked" and that wasnt such a big issue in those days. So do V-8s... and for that matter, any car that is equipped with a manual transmission is a great candidate for crankwalk(Mitsus more than any car though)

[puts on flame suit]

 

[2g617awd]

well my friend u answered your own question , the reason you dont need a new block is becuase your crank walk was caught early and didnt result in complete engine failure. some cases can be fixed, most can't. CASE CLOSED haha

 

[luvmygst]

The blocks become unusable when people let it go to long and the crank eats throug the bearing and gets into the block. If part of the bearing is left I would reuse it. The one in my car was a C/W block. With a proper build you should have no probs. I would make sure to replace or atleast clean out the oil squirters real good though. I am curious to know how he repaired the rod journals though. The only way I know is to spray weld and then grind it back down to factory specs. but you still lose the benifit of the nitride coating. But It may work fine. If it was me I would just have had it cut .10 on the rods, but thats me. Dont forget that even though you got the bearings with the vin number, to still check and double check the specs before you button up the bottom end. Good Luck.

 

[lee101315]

The blocks become unusable when people let it go to long and the crank eats throug the bearing and gets into the block. If part of the bearing is left I would reuse it. The one in my car was a C/W block. With a proper build you should have no probs. I would make sure to replace or atleast clean out the oil squirters real good though. I am curious to know how he repaired the rod journals though. The only way I know is to spray weld and then grind it back down to factory specs. but you still lose the benifit of the nitride coating. But It may work fine. If it was me I would just have had it cut .10 on the rods, but thats me. Dont forget that even though you got the bearings with the vin number, to still check and double check the specs before you button up the bottom end. Good Luck.

Yes, he welded them back up and cut them down to STD. Even if you grind it down as you said, I think you still lose the nitride coating.

All the bearings fit nicely, my only issue being that I had to adjust the center bearing for end play

 

[luvmygst]

Yes, he welded them back up and cut them down to STD. Even if you grind it down as you said, I think you still lose the nitride coating.

All the bearings fit nicely, my only issue being that I had to adjust the center bearing for end play

The cranks are supposed to be non-servicable as per the dealership. But oh well. everyone does it. The reason I said I would have cut it is that its one less thing to fail. No you have a weld in there that can come loose if not done perfectly, its just not as strong as cutting into the original crank.(IMO) BY fit nicley what were the clearances? just out of curiosity. How did you "adjust" the center bearing?

 

[Strm Trpr]

I've read on here that some guys have used this in the past with some success. http://machv.com/conracmbcadk.html

 

[ClassicalBor]

If you caught your crankwalk case early on like it seems you did as mentioned above, only thing you should have to worry about is that crank bearing all other parts should be intact if you caught it good and like you said you arent new to engines.. goodluck witht eh rebuild

 

[lee101315]

The cranks are supposed to be non-servicable as per the dealership. But oh well. everyone does it. The reason I said I would have cut it is that its one less thing to fail. No you have a weld in there that can come loose if not done perfectly, its just not as strong as cutting into the original crank.(IMO) BY fit nicley what were the clearances? just out of curiosity. How did you "adjust" the center bearing?

Well, as I went to install the crankshaft, I noticed that the thrust bearing was a bit too tight.
Meaning, the crank would not quite fit. When I called to return the product, the person in charge told me that the thrust bearing was sold in a "one size", and would have to be machined to fit the crank. And that is what I did.

The next adventure is to properly eliminate the balance shaft... that pain in the ass runs off of the oil pump; so I had to buy the kit

 

[The_one]

On the same topic, how bad of a "crank walk" when you discover that your crank angle sensor is broken ? Also what parts of the block do you need to replace/repair when something like that happen ? And where do you buy those parts?



Thanks,
V

 

[GVR4592]

Well, as I went to install the crankshaft, I noticed that the thrust bearing was a bit too tight.
Meaning, the crank would not quite fit. When I called to return the product, the person in charge told me that the thrust bearing was sold in a "one size", and would have to be machined to fit the crank. And that is what I did.

The next adventure is to properly eliminate the balance shaft... that pain in the ass runs off of the oil pump; so I had to buy the kit

Are you saying you machined the thrust bearing to fit the crank because the manufacturer told you to? When you installed the crank did you just drop it in and torque it down?

 

[lee101315]

Are you saying you machined the thrust bearing to fit the crank because the manufacturer told you to? When you installed the crank did you just drop it in and torque it down?

Yes, that is correct.
Did I "just" drop it in and torque it down? Yes I did, after double checking a few things.

1. Everything was spotless and oil squiters/lubrication holes were clean, and free of debris; that includes the crankshaft also.

2.Installing a .004" feeler gauge on one side of the main bearing cap and slightly tightening the bolts, just to make sure the main bearings fit first. Of course, it was removed during installation

3. Using that nice prelube on all moving parts

4. And do not forget to PRIME the oil pump!!!

 

[GVR4592]

It's probably going to walk again. Installing the crank isn't just a drop in procedure, and having to machine the thrust bearing is a good indicator the crank wasn't machined properly and/or installed properly.

 

[lee101315]

It's probably going to walk again. Installing the crank isn't just a drop in procedure, and having to machine the thrust bearing is a good indicator the crank wasn't machined properly and/or installed properly.

Please elaborate on the correct procedure to install the crank.

I do expect the crank to walk again, but not for many moons. Since mine walked at 140k, I would expect this to last at least 80k. Why? Nothing was done to correct the original cause.

You claim that "having to machine the thrust bearing is a good indicator the crank wasn't machined properly and/or installed properly". You are insinuating that something was done incorrectly. I have two questions:

1. What did I do improperly?

2. What did the machine shop I chose do improperly?

Some background on me:
My name is Lee, and I have been a technician on cars for 11 years. I manage a shop that specializes in certain German cars. All sorts of work is performed here, including engine rebuilds, electrical trouble shooting (a big nasty on these cars), basically everything minus bodywork. I, in no way, claim to be an expert who knows everything. I am still learning every day, and DSMs/Turbo tuning will be something new for me.