#4 main bearing:






#3 rod bearing:

 

Polish the crank and replace the bearings. Bearings are cheap as compared to the time and trouble that goes along with pulling and taking apart an engine.

 

Is polishing the crank absolutely necessary? And if I replace the bearings should I do the rings as well?

 

Why did you tear apart the motor if you aren't willing to do the basic things? Are you going to reuse the head gasket too?

 

Is there a way I can polish it at home or do I have to take it to a machine shop? The crank already feels pretty smooth, there's no scoring on it.

 

Just hit it all with some 80grit and send it

 

While a polish would definitely be better than nothing, you'd be fine without it. But absolutely for sure the bearings. And check the clearances after you have the new bearings in there.

 

Alright so I'll definitely replace the bearings. Would the piston rings be worn at this mileage? I can still see the factory cross-hatching on the cylinder walls. I'm just hesitant to change the rings, as then I'll have to worry about breaking them in while also tuning the motor when I put it in the car. Currently the car has a 1.6 and a megasquirt in it.

 

So why did you take it apart?

--Ian

 

The rings are up to you. I am confused as to why you took the engine apart if nothing seemed wrong? Compression issues? If not then the rings would be fine but you took it apart so replacing the rings would be a nice thing to do. If I had taken the engine apart I'd replace the rings but if nothing was wrong with the engine I wouldn't have taken it apart.

 

If it aint broke dont...oh

 

If i took apart a working motor........ Someone should probably sit me down and see if im alright.

 

I took the engine apart to replace all the gaskets, seals, and the oil and water pumps. I drove the donor car very briefly and the engine seemed healthy, although I didn't do any hard acceleration with it, as the exhaust had been cut off at the cat.

 

So you took the mains off?

 

I took off the #4 main to replace the thrust bearings.

 

So the thrust bearing was bad?

 

If you've already got the crank out in the open you may as well replace the bearings.
As for rings, i'd personally replace them too, they're easy to do at this stage, but a dick to do once the engine it back in.



For break in, if the tune isn't good enough as is, just throw the factory ECU back in for bedding the rings etc.

 

I can't put the stock ECU back in since the engine is from an NB and its going into an NA. I'm hoping it'll run ok with the fuel map from the 1.6 tune on first startup.

 

Just load the NB base map from DIY

 

You have done roughly 90% of the work and incurred roughly 50% of the cost of changing the rings. Leaving them in place at this point would be foolish.