Friday, December 30, 2011

'99 Miata Camshaft Confusion!

With the help of a couple friends, I figured out why my new '99 head was making such a racket. It's got the wrong exhaust cam in it. I got the '99 head from a friend of mine. It's been in storage for over 10 years and its exact history is a little fuzzy. It came completely assembled but the cams were just loosely held in the journals with the bearing cap bolts finger tight. As seen much earlier in this blog, I took it apart and lapped the valves, checked the bottom surface for straightness, and put it back together.

What I've been hearing since I first started it up was what sounded like excessive valve lash. It was quite loud so I knew something wasn't right. I had checked all the clearances when I installed the head and they were pretty good. If anything a couple of them were on the tight side, not loose. Nevertheless, I figured I had screwed something up so this morning I popped the valve cover off and measured the clearances. None were above the maximum spec, but a couple were below the minimum, so I fired up my spreadsheet and plugged in all the numbers and identified 4 shims I could swap with each other that would bring everything within the factory specs. I was able to get the shims out without completely taking out the cams or having to re-do the timing. If you loosen the bearing caps and rotate the engine you can sneak the shims out from under the cam without removing the timing belt.

I was very glad to get the clearances better adjusted. Most of the valves are in the bottom half of the range. Alas, the noise was unchanged, so I put out a mayday to some gearhead buddies. One of them asked if I was sure I was using the right cams because the cams for NA and NBs have a different profile due to (or at least coincident with) the change to solid lifters in '99. I just used the cams that came with the head, but I realized that I took it on faith that they were the right cams.

Note the NB cam on the left has a more rounded profile, while the cam on the right from an NA is more pointy.

So, I pulled the valve cover off again and held a cam from a '96 next to the cam installed in my '99 head. They look the same to me. It was starting to make sense.
Next to the intake cam in my '99 head: The known '96 cam looks a little more pointy compared to the intake cam in my '99 head, as would be expected.

To seal the deal, I spotted the marking on the intake cam, BP4W, which is indeed the correct intake cam for the head. On the exhaust cam is BP06, which is an NA cam. Bzzt. Wrong cam. So I'll be ordering up an NB exhaust cam and I'm debating whether to also order the BP5A (aka Mazdaspeed cam) for the intake side. Would be easy to swap it out as long as I'm in there swappin'. Hope this helps save someone some trouble sometime. Never assume!

Sunday, December 18, 2011

Refurb Results!

The car is pretty much done! I'm just taking care of details at this point. I still have to wet sand and polish the whole car to correct some flaws in the paint. I'll try to document that as I go. I'm also going to revisit the valve adjustment. The car runs like a scalded cat, but the valves are noisier than I think they should be. I just want to check it again and try to get the clearances down to the bottom half of the specs. This is the downside of getting rid of the Hydraulic Lash Adjusters from the '94 head.
Here's the car on its first outing! The hood is still unpolished after wet sanding but you can't see it too much in this picture. The Reptile Red paint really pops in the sunlight. It's insanely red!
The engine money-shot.
This shot shows the color in more normal lighting.
I replaced the instrument lighting with LEDs. This doesn't make a huge difference except the needles are now white instead of green.
This came in the brown truck the other day.
It replaced the 12 year old MOMO Champion that was getting quite ratty. I love the red stitching and will probably mimic that on the seat upholstery when I do that.

Saturday, December 10, 2011

Painting Miata, Part 4

So here's the end of the first day of painting. I got three coats on the car. The first coat looked like crap because I hadn't got my technique down yet. The second coat made things a lot better and the paint was starting to flow out better and look glossy. After the second coat I sanded down some small nibs with 600 grit wet sandpaper and cleaned the gun before spraying a third coat. I didn't get the sprayer adjusted just right after I put it back together and it was putting down a lot more paint than before. I got greedy, because it was flowing out so nicely and looking really good, and I ended up with a few small sags that I will have to go back and fix.
The hood is really hard because it's difficult to reach all the way to the middle and keep the gun at a constant angle and velocity.
This is the paint. It's called Reptile Red and it's a bit brighter than the Mazda Classic Red, but definitely in the same family. It's a 3:1 mix so they sell you 3/4 of a gallon and then you add 1/4 of the activator. If you were going to spray the whole gallon all at once you could just dump the activator in the can with the paint and go. Once you do that, though, you only have about 2 hours until it starts to gel.
Next I have to fix the sags and then I can spray clear. It still looks kinda "raw" and probably won't all come together until the clear is on and cured and I can really give it a good buffing with the random orbit polisher.

Sunday, December 04, 2011

Painting Miata, Part 3

This weekend I started spraying paint. Since the car is mostly stripped down, the job of masking is pretty minimal. This photo shows the car more or less ready to shoot with primer.
Safety first! Painting involves some pretty nasty solvents and particulates in the air. Proper protection of lungs and skin is essential.
This is as far as I got the first day. I was having trouble with my HVLP spray gun and decided to stop and make a couple improvements to my air system. I installed a bigger air regulator and a new inline filter. It seemed to do the trick once I learned how to set the gun up right and I got much better results.
Primer before sanding.
So this is where I left off tonight. The primer is all sprayed and I've gone over the whole car with 400 grit dry paper. Before next weekend I have to wet sand the whole car with 600 grit and then I'll be ready to spray color and clear.