Sunday, October 02, 2011

Miata engine refurb stuff

So this weekend I got into re-doing the engine. I got the block cleaned up and painted, the pistons cleaned, the '99 head disassembled and cleaned, and the intake manifold cleaned, painted and reassembled. Note that I'm using the term refurb and not rebuild. I did a compression test before I took everything apart and it had 170 psi across the board, so even though this engine has 155,000 miles on it I'm going to leave it alone for now. If it needs a rebuild later I'll take that opportunity to put higher compression pistons in.
After degreasing and pressure washing I used painter's tape to mask off the deck, oil pump body, and all the exposed machined surfaces. Then I just sprayed the block with red engine enamel. It turned out nice!
Here's the '99 cylinder head with the cams off and the lifters out. My next step was to use my valve spring compressor to remove the valves. See my earlier blog post where I posted a video on how to remove the valves. I used a plastic storage organizer with 16 compartments in it to keep each valve together with its tappet, shim, spring, retainer, and keepers. I want them to go back in the same hole they came out of.
Here's the bottom two-thirds of the intake manifold. This is a great view of the butterflies that make up the VICS system. These butterflies are closed by default but open (or I may have that backwards) at a certain RPM (on '99 and '00 models) to a resonance chamber. The chamber is a dead-end so the path the air takes doesn't actually change when the system engages. This won't work at all on my '94 unless I rig up an RPM switch and a solenoid to engage the actuator. Even without VICS hooked up the '99 head makes more power than the '94 head, so it's a good swap either way.
Here's the '99 intake manifold fully assembled and the '94 throttle body installed. I found the water connections on my idle air control valve are quite corroded so I may devise a way to just bypass it. I painted the manifold with Aluma-Blast from Eastwood and it looks fantastic. The throttle body is too complicated and intricate to spray so I polished it up as well as I could with a soft brass wire wheel on my right-angle die grinder.
The '99 head came with a pretty fresh cam cover so I degreased it and painted it with Aluma-Blast.

Here's a few more photos from this weekend.

Here's one of the solid lifters with the shim attached. I pulled out all 16 lifters and measured the shims. One lifter was missing its shim entirely. I had to make a best-guess as to what size shim would work best in the spot, so I just ordered a couple that were close in size to all the other shims on the intake cam. The ones available from Mazda were mostly not close in size to the shims I have so it may be tricky to get everything in spec. I can't go any farther with the head until I get that shim but it should be here by next weekend.

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