Quickie 2.0 Rebuild Options

[McMark]

One of my winter tasks is to build a stock 2.0 with my MicroSquirt fuel injection that I can install in my car and get it dyno tuned. That's been the missing piece of my MicroSquirt setup for the last few years.

Since there isn't much demand for a stock 2.0, I just plan on doing the minimum to build a solid motor. I plan on having the valves reground, cylinder surfaces machined and reringing the pistons. Regrinding the cam and rebuilding the rods and all new bearings as well. This should give me a motor that will last through the testing, and be worth something when I'm done to pass on to a new owner at a nice price.

This thread does not represent my standard procedures for rebuilding engines. This is a special case and special circumstances.

For those of you on a budget, but looking to refresh their motor should appreciate this writeup.

Starting off with a core engine. The previous owner mentioned this engine had a 'knock', so I'll be on the lookout for what might have caused that. This is a 'GC' code engine with air injection ports in the heads.

[McMark]

Without giving away any proprietary secrets, could you give an example of tools and procedures you would use to correct damage from driving out wrist pins the wrong way? I may have, ahem, seen a piston with some dings like this before.

There's no real secrets in engine building, IMHO. It's all been done before. I don't feel people hire me to build engines because I 'know the secrets', but rather because I have the experience, muscle memory, and know what parts feel like when they're right. It's not the knowledge, it's the skill to feel when something isn't quite right and that's something you can't type out or take a picture of. So feel free to ask for the 'secrets'. (IMG:style_emoticons/default/wink.gif)

I used a small 'half-round' file to bring down most of the raised material. Working slowly with light pressure. With each stroke, I'm paying attention to the angle of the file to make sure it's parallel to the bore-wall. I'm also paying attention to the feeling/feedback from the file, noticing how it feels when I first start and paying attention to how that 'chattery' feeling goes away as the protrusions get smaller and smaller. Once I feel I've taken a good 75-85% of the bumps out, I stop and clean the bore and test fit the wrist pin. The first time it never goes in, but I don't want it to. Processes like this should be approached by inching towards perfect, not by trying to hit the target in one shot. Imagine you're running towards the edge of the Grand Canyon, do you want to run flat out and then stop at the last second? Or slowly approach the edge? The former may be impressive when done right, but I'm not here to impress anyone. I'm here to do it right, and a slow methodical approach accomplishes that safely and repeatably. Go too far in filing a wrist pin bore and you're weakening it. Anyway, after a few iterations the pin will slide in, but not smoothly. Pull it back out and look for shiny spots that indicate where the pin and bore are contacting firmly. Focus on those areas, and then switch to some fine sandpaper. I was using old, already worn down 400grit. I would probably grab 800-1200grit if I was using fresh sandpaper.

And speaking of weakening. This technique is not 'correct'. If these were rare pistons that I had no choice but to reuse, and they had this damage I would be outsourcing this to someone who had the correct honing tools to refresh the bore. But this build is about making do with what you've got in front of you. It's about building a engine that's just a little tighter than it was before. If you're looking for ultimate longevity, build a new motor. (IMG:style_emoticons/default/tongue.gif)

So with that in mind (again) I don't think this process is really reducing the strength if done right. If the red circle is the original bore and the blue section is what's left after I file everything down you can see the pin still has original contact and support over a large segment. And by approaching it slowly, that blue line is a HUGE exaggeration of what I did. My final wrist pin bores probably still have WELL above 95% of their original contact area. Probably above 98%.