I know I said this was going to be a long-term project and this is my third update in just a matter of days. But the actual swap will still be a long-term thing. However, I’ve been busy with prep and decided to lay out some thoughts on it as I learn more.
First thing was to clean up the head and see what I’m dealing with. As seen in the last update, it’s in overall good shape and fairly well cleaned up. Cylinder 4 still has stains and stuck on build up from getting water in it. But overall, it’s in good shape.
I know I still need to do a final clean on it, but I also wanted to have a machine shop check it for warping and shave it to make sure it has a flat mating surface. This is the part I’m at right now. I found the specs for the head and Mazda allows a maximum warp of 0.002in when measured with a straight edge from multiple angles.
The thinnest feeler gauge I had on me when I decided to measure this a few days ago was 0.006 and it passed that with flying colors. So at least I knew it wasn’t a boat anchor yet. I ordered up a new set of feeler gauges that went down to 0.0015. As soon as they arrived, I set out measuring from multiple spots and angles.
I started with 0.004. That’s double the maximum allowable warpage, but I guess I wanted to add some drama to my night.
It passed.
0.003….passed.
Then it was time for 0.002. Technically if this gauge slid under, I should still be ok as that was the allowable amount.
But it passed.
Happy that the head was within spec, I went to my thinnest one available. 0.0015. It’s razor thin. I didn’t think there was any way it would pass. It felt like I was measuring with a strip of paper. But I set the straight edge on the head, measuring it in multiple places from all the specified angles from Mazda.
It passed every single one.
The head is straight, or “true” as some might call it. So there is really no need to have it decked. At this point I was thinking of just a very thin skim just to clean the mating surface. I contacted a few local machine shops and all basically told me the same thing after looking into it. They said Mazda doesn’t really recommend removing any material from the head due to the very tight tolerances of the Skyactiv engine. None of them actually told me no. They were all willing to do the work. But they gave the warning that Mazda does not officially recommend it.
So now I’m thinking of just cleaning out the rest of the cylinder 4 bowl and calling that part good. The mating surface is fine, just needs some staining removed which will take some elbow grease. I still haven’t even touched the valves other than verifying that they all seal fine. I have a think coating of oil on them and the seals to keep them from drying out. Visually they seem OK. The only reason I can see to remove them would be to replace the seals and guides. Now would be the perfect time.
This finish line is still months away. But I wanted to share this info so you can see the condition of the head. The fact that it’s straight with no measurable warping (by me anyway) is exciting. I still need to acquire an ND2 intake manifold. I’m also going to get a new timing chain and tensioner given the miles on mine. While I’m in there the front main seal will also get replaced.
Miatas at the Gap took most of my “fun money”. I’ll need to refill that stash before getting any more parts for this project. I’ll continue to update as I make progress, but they may be fewer from here on out.
Supergoat Garage 