Since I’m doing the head gasket, I’m taking my time with everything. I’m doing the timing belt and water pump. I’m changing out every damn seal I can find. Hell, I took a vacation to Las Vegas in the middle of this project.
And while I was on vacation, I got a little head work done.
Sorry to not have more in-progress pix to share. As I said above, there was a vacation. The only stuff I personally did to this head was port the exhaust. I paid for the rest of the work (thanks Soren!). And you know, I’m okay with that. I normally do EVERYTHING to Sharka myself. But there are limits to my ability and my tool collection.
I do not know how to port a head without ruining it. I was shown what to do with the exhaust ports (thanks Soren!) and would have destroyed them otherwise. And I stopped by the shop while the head was being put back together after it came back from getting decked. Holy God. The little keepers for the valves? I’m very pleased that I didn’t have to put those back in. That’s gotta be in the top 5 of Most Annoying Automotive Tasks.
Anyways, I digress. More pix of the head work.
Nothing was re-engineered. Everything was just smoothed out and gasket matched. Nothing crazy. And that’s just what I wanted.
I’ve read “why do head work? Just turn up the boost one pound” more than once. So… why? My answer is “because I was there.” The head was off. Why not take the opportunity to let it flow a bit better? The benefits can be quicker spool, more power for less boost pressure, and other such good stuff. But really, I’ve never had a head off any of my Miata engines. It seemed like something fun to do. So I did.
Mazda says that a head can be machined by .008″ before it’s “done” and needs to be trashed in favor of a new one. The stock head gasket is 1 mm thick, or about .039″. So, they’re saying the head can warp only 20% of the head gasket thickness before it’s unusable. That seems…. incredibly cautious to me. But I’m not the most knowledgeable ever about this stuff.
Anyways, my head required only .002″ of machining to get it back to flat. I’m quite pleased with this.
As you can see, I didn’t have anything done to the area around the valves (the bowl). It was just cleaned up and then the valves re-lapped. After putting it back together, we adjusted the valves. 3 out of the 16 were out of spec slightly, all on the intake side. That’s not bad.
So, that’s it! Sharka’s head is all machined and ready to go back in the car. At the time of this writing, that has not yet happened. I’m waiting on some coolant re-route parts from BEGi and a few more seals from Mazda. With any luck, those last parts will get here shortly and I’ll have more stuff to do and take photos of.
(I really hate waiting for parts to get mailed…)