I covered this in the engine removal post, but I rebuilt my engine because my crank bolt was loose and had chewed into the keyway a little bit. Mine was no where near as bad as other I have seen on the internet. I do believe it was bad enough that I was running 1-2 degrees retarded timing. I can't currently confirm this because I didn't think that was the problem at the time and I took it all apart and didn't want to put it back together to check it with a timing light. But I will say, while I am not the best driver in the world, I was being beaten by completely stock Miata's at autocross events by ~4 seconds depending on the course. So we will see if this helps liven up the motor a little bit and help with that.
If you have a worn out keyway, one option to fix it rather than take the whole engine apart and replace the crankshaft like me is to use Loctite 660 to repair it. There are plenty of walk-throughs out there that show you how to do this. Loctite 660 is specifically made to repair bad keyways in machines and people seem to have good luck with the fix if yours isn't too worn out. My engine was a good candidate for this fix, but now that I plan to turbo I was going to replace the piston rods anyways.
Lastly, before we get into it, if you want to rebuild an engine but are afraid of tackling a project like this, it really isn't that bad. If your car is a fun car and isn't needed for daily driving or anything like that, I highly recommend picking up a Grainger Manual (or similar) and learning something new. This book walks you through how to rebuild an engine and is a great resource for plenty of other maintenance things. On top of that, if it is a miata you have, there is no better car community out there willing to help people solve problems. You are all wonderful people and I thank everyone who has helped me get my car to where it is today!
Preparing the Engine for Work
You are going to want to clean the engine as best you can. As the parts come off you will be able to clean them better, but it is helpful to start with a clean engine. Use some engine de-greaser, a brush, and a hose to clean off what you can. Of course mind the electronics when you do this. If you didn't already do it in the car, while the engine and transmission are on the hoist, NOW is the time to drain the rest of the fluids and let it sit for a little.
In usual Ray fashion, I didn't take any pictures of this process, but next you need to unbolt the transmission and put it somewhere. The thing ways ~60lbs, it is pretty easy to carry by yourself, but as always have a second hand or set it up on something in case you have problems. Next is the flywheel. This likes to spin while you try to get it off. Use either an impact gun, or a decent sized flat blade screw driver and put one of the transmission bolts back in for leverage to hold the thing. You should now have access to the back of the engine to mount it to the engine stand.
Engine Mounting
First thing is first, you need to get the engine somewhere that you can work on it. I had an engine stand and I welded up some fingers to use to attach it since the originals fingers were missing from the stand. If you want to make your own I used:- 1" x 1" x .120" low carbon tube ( I got 3' and had just a little left over)
- .625" x .065" Tube (Got 1' of this)
- M12 x 1.5 x100mm bolts (This ended up being a little long 90mm would be better)
- M12 x 1.5 Nuts and Washers
I am going off memory about this as I don't have them right in front of me right now, but I believe I cut (4x) 6" sections of square tube. I drilled them to .625" so the tube would slide through. I then cut (4x) 2" sections of the round tube and slid them in and welded them. I then marked the hole locations for the plate that was on the engine stand and drilled them out. Then I bolted it all together as seen below. I may have made adjustments from what I have above, so double check your work as you go through this.
Removing External Components
Next is to start removing everything still attached to the outside of the engine. Depending on what you took off with it still in the car this might vary. But I had to remove things like the intake manifold, fuel rail and injectors, EGR components, misc brackets. This part is easy to do and because of that it is easy to do it quickly and forget to label stuff! LABEL EVERYTHING AND TAKE PICTURES OF EVERYTHING. I was trying to be really conscious of this while I was removing stuff, but as I put it back together there have been plenty of mystery parts that have taken a fair bit of time to figure out where they go.
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| A smattering of the photos I took |
Remove the Rest!
With all the external components off you should have a basic looking engine with an oil pan, block, cylinder head, and valve cover, plus or minus a couple of things. Start by removing the valve cover. The Grainger manual recommends starting in the middle and spiraling outwards to loosen AND tighten the bolts. While I can see this for tightening them, I am not sold on it for loosening. But DO IT ANYWAYS, it surely won't hurt.
With this off you will be able to see the bolts holding the cylinder head on. Do the same process as the valve cover. Start in the middle and spiral out to loosen these and take the cylinder head off.
You should be left with something like I have shown above. I will not be covering how to adjust the valve lash and stuff for the cylinder head as I had someone do the work for me. It was ~$275 to get the valve seats re-cut, the valves ground, seals replaced, lash adjusted (with the stupid shim type system), gaskets replaced, head checked for flatness and re-milled, and likely a couple other small things I am forgetting. If you want to do it yourself, great! But I recommend letting someone who has done a ton of them do it for a reasonable price unless you have the proper tools.
Now we turn the engine over to get the oil pan off. Remove all of the bolts around the pan. Using a small screwdriver or sheet rock knife, break the seal of the pan to the block. HERE IS WHERE THINGS CAN BE TRICKY! Mine was so covered in sealant I couldn't see where it was, but there is an oil baffle that gets sandwiched between the oil pan and the block. When you break the oil pan free, if the baffle is still stuck to it, you won't be able to get the oil pan off. It will seem loose but something 'springy' will be keeping it held on. If this happens DO NOT PULL ON THE OIL PAN! YOU HEAR ME! You will need to take you knife and cut along the sealing surface of the pan to try and cut/pry the baffle off of the oil pan.
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| This is the baffle and the block still together. The oil pan sits on top of the baffle and sandwiches it between it and the block |
The baffle is bolted to the oil intake tube, which is why you don't want to pull on it too hard. If you do, you risk bending that tube which you will then need to replace.
Remove the Crank, Pistons, and Oil Pump
BEFORE YOU DO ANYTHING, take 4 paper towels and label them Cyl #1, Cyl #2, Cyl #3, and Cyl #4. If you plan on re-using any of the internals, you need to keep track of where they all go, If you are replacing everything, then this part is good to still do in case something goes wrong and you end up needing something. With the engine still flipped over, you now have access to the crankshaft and main bearings. Rotate the crank shaft to some point where you can access all the rod end caps.
Take a punch and punch the bottom of the end caps with a dot(s) for what the cylinder number is. 1 dot for cylinder 1, 4 dots for cylinder 4. With this done you can now loosen and remove the end caps, putting them and their bearings on the respective paper towel. CAREFULLY push the pistons down to a point where they are out of the way as you will likely not be able to get them out at this time.
Loosen and remove the crankshaft main bearing caps. These should all be labeled and with an arrow that points to the front of the engine. Double check and remark if you are uncertain about the markings on some. Make sure to get the thrust washers off of the fourth main cap. With these removed, the crankshaft is now loose and can be carefully lifted out of the engine. Make sure not to scratch the journals on the piston rods or anything else.
With the crank out, you can now push the pistons the rest of the way out. There is likely carbon build up on the top side of the cylinders. This may need to be cleaned off with some carb cleaner and elbow grease before the pistons will slide out. Remove the oil sprayers that are on the bottom of the cylinders and keep them with the correct cylinder. Mine had no copper washers, but it seems like the pre-NB 1.8L engines had them.
If you have not already, remove the oil pump.
Using your punch, mark the piston rods and the bottom side of the pistons in the same fashion as the bearing caps for the cylinders that they correspond to.
Using your punch, mark the piston rods and the bottom side of the pistons in the same fashion as the bearing caps for the cylinders that they correspond to.
