Sunday, October 09, 2011

Miata Cylinder Head Assembly and Installation

This weekend I concentrated on getting the engine together. The '99 head is going on the '94 short block. I had to install the valves in the head, and before I could do that I had to clean up the valves and lap them into their respective seats. The valve seats were in really very good shape so it only took a minute or so to lap each valve and get a really nice seal to the valve seat.
The valves cleaned up very nicely. They had some carbon deposits that were pretty stubborn but my trusty brass wire brush on my right angle die grinder finally got to the bottom of it.
This $3 valve lapping tool worked just fine. I used some Permatex valve lapping compound, which is very abrasive. It's super important not to leave any in the engine. It's a little hard to see in the above photo, but what you must achieve is a uniform seat surface without any gaps or thin spots. It should be the same width all the way around. Since this head has such low mileage, the valves took very little lapping.
I had to make a tool to install the valve keepers. A 22mm socket with a window cut in it did the trick. Installing the keepers is an EXTREME exercise in patience. Working through a one-inch hole to get the tiny keepers into a tight spot is frustrating to say the least. I developed my technique - sticking the keeper on the end of a small wood dowel (ok, it was a chopstick) with a gob of grease, and finessing it into position next to the valve stem and inside the retainer, and then do it again with the other keeper without disturbing the first one, then releasing the spring compressor without the whole thing coming apart. I got decently adept at it within the first 5 valves, but then for every 3 that go together very easily in just a few seconds, the fourth one fights you for some reason and takes 30 minutes to get done. In my earlier years I would have broken some things. There are some benefits to growing older and more patient.
This is the coolant fitting on the back of the '94 head. For some reason it got really badly corroded. It was leaking coolant onto the top of the transmission bell housing.
For about 20 bucks I got a new one. I just had to transfer the temperature sensors over.
This is why doing a restoration takes a lot longer than you think it will. This bracket came off the back of the '94 cylinder head. I don't even know what it is for, but I decided to transfer it to the new head, and spent almost an hour wire-brushing the rust and grunge off of it, and painting it with aluminum paint. If this was a REAL restoration I'd have to have it cadmium plated.
Next I fitted the head gasket. Note that it will fit in any orientation but there is only ONE orientation where all the correct coolant and oil passages are clear. I checked it and double-checked it to make sure I got it right.
I bolted the head down, torquing the bolts in a spiral pattern from the middle, to 58 foot-pounds. Then I dropped the lifters in.
Next I installed the cams, the cam bearing caps, and torqued them down to 115 INCH-pounds. Actually, I don't have a torque wrench that reads inch-pounds, so I very carefully used my 3/8" torque wrench set to 10 foot pounds. I also went ahead and installed the water neck with a new o-ring, and installed the cam gears torqued to 40 foot-pounds.
Next I installed the water pump, the outlet pipe, and set the cam cover on top for good looks. It's not bolted down yet. The water pump bolts are torqued to 16 foot-pounds.

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