Spun Rod Bearing- Crank Question

[GVTalon]

My 95 Tsi was a victim to crankwalk while I was trying to sell it (Just my Luck). About a year a go I bought a 97 4G63 shortblock with crank pistons and rods from a guy off the trader with a spun rod bearing. He said it had 40,000 miles on it. I picked it up in person and the motor was disassembled and he showed me which bearing had spun. There is just a small rust spot on the surface of the crank where the bearing let go. There are no deep groves. I would like to reassemble the shortblock and put it in the 95 to sell it. How do I go about checking the tolerances to see if the crank needs to be machined? Or should I just have it machined? Or should I just polish the rust spot, get new bearings and throw it back together since there are no grooves? I want to do this a cheap as possible since I’ll just be selling the car once it’s done.

 

[JET]

You have to get the crank polished. If you don't it will trash another bearing in a matter of miles. It shouldn't be too expensive, but you will need new crank bearings too.

 

[OMN_DSM]

A crank regrind is around $75 but if there is very minimal damage than you could probably get away with a micro polish which will usually run around $45. Good luck!

Mike

 

[GVTalon]

Do you think the micro polish is something I might be able to do? I have a high rpm industrial buffer and a load of professional grade compounds from coarse to super fine. Would I just be polishing the rusted area or would this cause a flat-spot? Thanks for the info guys.

 

[OMN_DSM]

No, you will have to take it to a machine shop, because it wil have to be the exact same all the way around. And they wil be able to tell you whether or not you will need a polish or a regrind.

Mike

 

[GVTalon]

Ok thanks. Now I just need to find a decent shop around here.

 

[GSX_RCR]

Is there any DSM shops that can turn a crank? I don't really trust the machine shops around here. I don't mind shipping it out, as long as it's done right.

 

[OMN_DSM]

Bj's cylinder head I have only heard good things about there work and thats where I plan on sending my stuff to get machined.

Mike

 

[rdrkt]

If you are getting another 7bolt block built you are courting disaster. Most machine shops WILL NOT be able to machine and assemble your motor properly ESPECIALLY with a reground crank. Be forewarned go 6bolt or be prepared to redo it down the line.

 

[GVTalon]

As I mentioned in my first post I'm only rebuilding a 7-bolt block to get the car running to sell it. It would not benefit me at all to install a 6-bolt in a car I will never drive again.

 

[GSX_RCR]

Well, I hope you don't forget to mention that to the buyer when you're selling the car.

So you guys don't think it's worth it to rebuild a 7 bolt?

 

[rdrkt]

Originally posted by GSX_RCR
So you guys don't think it's worth it to rebuild a 7 bolt?

NO!
Most of the time unless you have a FANTASTIC machine shop (and sometimes even if you do ) the job will get screwed up. Im not a mechanic nor do I play one on the internet but from what I have heard its pretty damn hard to get the mains lined up just right and the job is made that much harder when you do crank work. Many people have said that they know better than everyone else. That their machine shop is 10x better than any other DSM shop out their only to end up regretting their decision 6 months down the line and spending money twice.

Gvtalon: I would not want to be in the position of having to deal with motor issues a few months after you sell your car.

 

[GVTalon]

rdrkt- I very much agree with you that there are potential problems when rebuilding an engine, especially a 7-bolt and if I were building an engine for my car it would without a doubt be an unharmed 6-bolt.

Just to explain my situation, I have a 95 base model Tsi with a crankwalked engine and 176,000 miles on the odometer sitting in my driveway. To sell the car at as a whole, it would need to be in running condition and the seller would have to accept the car "as is" because of its high mileage. I would inform them of the history of the shortblock of course. There is just no sense in me spending $1000+ on a new 6 or 7 bolt engine that I will never use and for a car that I will only get $4000 max for. So for me having the small rust spot on the crank polished and mic-ing the journal to get the correct rod bearing size and throwing the engine back together is the most economical route to sell a running car in "as is” condition.