CompuServe Magazine, September 1995

It's by pure coincidence that I saved this issue. I didn't own a Miata in 1995.

BMW M3 Valve Adjustment, S54 Engine

My M3 is way overdue for a valve adjustment. The maintenance schedule calls for doing it at every inpection interval which is roughly every 30,000 miles. I've had this car for 19,000 miles but I have no record of it ever being done. It probably was done at least once, but I'm betting it's way overdue. When I measured the clearances, every valve was out of spec, and all were on the "loose" side of the spec, which is actually better than them being on the "tight" side. They weren't really TOO far out of spec, considering. Just a few hundredths of a millimeter, on average. The worst one was 0.08mm out of spec. The car has 102,000 miles on it now so I want to get it in spec and give everything a good going-over so it will be ready for the next 100,000 miles. As usual with this blog, this is not a "how-to" but rather a "you can". On my difficulty scale of 1 to 10, with 1 being putting air in the tires, and 10 being an engine rebuild, this is about a 3. Seriously, it's not hard. All you need is your basic hand tools, the BMW shim removal tool, and a digital micrometer. I paid about $30 for a cheap-ish micrometer specifically for this job. I paid $30 plus a crazy $20 for shipping for the shim removal tool, and I'm spending about $50 on shims. If you need to get this done in one day you'll need to buy the full shim kit which is about $375 but that includes the removal tool and when you're done you can easily sell it online for most of what you paid. I didn't do that so my car will be down for about a week while I wait for the shims to come from Pelican Parts. So I'm into this for about $130 and maybe 4 hours of labor, probably 5 by the time I'm done. A shop quoted me close to $1000 for this service, so it's a good DIY project. I referred to an excellent video on YouTube that covers the project in good detail. I definitely recommend you watch a couple of those before you start.

Valve cover is off and I'm ready to start measuring clearances and removing shims. It takes about 30 minutes to get to this point.

Here's my spreadsheet where I recorded all the clearances, the thickness of each shim, and do a little math to find out what size shim would give me the exact clearance I want. I calculated the Theoretical Best Shim (TBS), and compared that to the shims I actually have (24 of them) to identify which shim should go in each location. Doing this, I was able to reuse 14 of the 24 shims. I have to buy the remaining 10 because none of the 10 I have left are the right thickness. No way I could have kept all this straight without a spreadsheet. It took me a couple hours working slowly to measure and record all the data.

Here's where I laid out my shims to keep them straight until I did all the math. A few have already been put back in the engine in this photo. Now that I have the exhaust side all done, and none of the remaining shims can be used except two on the intake side, I no longer have need of these shims or this sheet of paper.

Here's the official BMW shim removal tool. I say removal tool because it was far harder to put the shims back than it was to get them out. This little plastic tool was almost $50 with shipping and everything, but it's a necessary evil. I finally got the hang of using it to put shims back in, but not before dropping a few shims. It is IMPERATIVE to block all the little oil passages in the head so that errant shims can't disappear into the engine.  That would be BAD. A magnetic pickup tool helps fish them out from where they fall. God help you if you lose one in the engine.

This is the micrometer I bought for this job. It was in the $30 range at Harbor Freight. It may not be extremely accurate, or it could be that I just had to learn to use it. That thousandth's decimal place should definitely be taken with a grain of salt.

UPDATE: 5/14/2011

The shims I ordered from Pelican Parts on Sunday arrived via USPS on Friday. Perfect timing. So this morning I finished the job. Unfortunately, when I put the new shims in place, most of the clearances turned out tighter than I had calculated them to be with my spreadsheet. A couple were just under the minimum and I wasn't comfortable with that. Upon re-measuring things today, everything was measuring bigger. Checking my technique with the micrometer with the new shims of known thickness, I think I was cranking down too hard on the micrometer last week. You can definitely influence the measurement by how hard you turn down the dial. Once I standardized my technique and got consistent results, I ended up re-measuring all the clearances and moved several shims around to get closer to the clearances I wanted. My main concern was to not leave any valves too tight as that can lead to problems. In the end, I got all the clearances on the lower end of the tolerances. The minimums are 0.18mm on the intake cam, and 0.28 on the exhaust cam, while the maximums are 0.23mm and 0.33mm for the intake and exhaust, respectively.

Most interestingly, and to my surprise, the engine really does feel smoother and a little bit quieter after the adjustment. I swear I can feel and hear the difference. I didn't expect to. The S54 really likes proper maintenance. I also took this job as an opportunity to inspect the bolts on the VANOS system as there have been internet reports of them backing out and causing catastrophic failure of the timing gears and chain. Everything looked absolutely perfect so I didn't touch a thing there. I feel better having had a look at them, though.

Removing Valves from the Miata cylinder head

The '94 runs well but not like it did back in the day. My goal is to get it back like it was, and make it run like a scalded cat on the track again. So I'm starting on this extra head I've had in the cabinet for the last six years. The mating surface needs to be cleaned up so I'm going to take it to a machine shop to get planed and cleaned and the valve seats re-ground. I can to do the reassembly here and then I'm going to yank the motor and swap the heads out of the car so I can also address the leaking rear main seal, install a light flywheel, new clutch, new timing belt, water pump, and front main seal. I don't believe the bottom end needs a rebuild, however. The existing timing belt only has about 30k miles on it but if I've got it all apart I'm going to replace everything I touch.
So today I disassembled this '96 head with 60k miles on it. I bought it on eBay about six years ago and ended up not using it, so it's been sitting in a cabinet ever since.

RAM iPhone, Camera, GPS mount

iPhone and camera mounts for motorcycle, from RAM
I got mine from Amazon for around $30. Very well made piece of hardware and works great. I do not think my phone is going to fall off in normal riding conditions. Of course it's not waterproof so at the first hint of rain the phone or camera have to get put away. I believe they do offer some waterproof options.

aSmartHUD app for time/speed/distance/music

MotionX GPS app for navigation

Standard camera mount

Fully articulated arm. Swapping camera and phone mounts takes just a few seconds.

Acceptable jacking points on a '90-'05 Miata

I lifted this image from a post at Miataforum and added some additional jacking points that weren't called out in the original image. You can tell which ones I added because they look like they were drawn by a 6-year old.

The four inner-most points indicated in the image are at the ends of the "frame rails" which are actually just floor panel stiffeners. Jack right on the ends of them where they are stronger, where the yellow ovals are in the image.

Bremmers for the Bimmer

So it was time for some new tires for the M3. The Nitto Invo tires it came with were almost down to the wear bars and getting really hard and noisy. I had put almost 20,000 miles on them and they weren't close to new when I got them. I took the opportunity to update the looks of the car as well by adding a set of Bremmer BR05's to my order from The Tire Rack. The BR05 is basically a reproduction of the wheels BMW put on the CSL version of the M3. Well, not really a reproduction but I guess a reasonable facsimile without the associated cost. These are only about $660 a set in 18" size. They are 18x8 in the front and 18x9 in the back, exactly like the factory wheels my car came with. I think the offset in the front is a little bit less than stock because it looks like the wheel sticks out just a bit more. I'll have to look up the exact numbers and see for sure.

Click for full size photo

The black finish is something different for me and I really like the slim machined lip around the outside of the wheel face. The tires are Sumitomo HTR ZIII in 225/45ZR-18 in the front and 255/40ZR-18 in the back. They came perfectly balanced from Tire Rack and ready to mount. The Sumitomos are an underrated tire in my opinion. The Boxster I had came with them and I thought they were great, and the price is very reasonable at around $600 for the set in M3 sizes. They aren't for autocrossing or track days, but for street driving they are a great value.

Miata Battery Alternatives

Early Miatas came with an excellent AGM type battery that has been known to last upwards of 10 years with proper care and feeding. As nothing lasts forever, sometimes a replacement battery is needed. I've relied on a battery from Westco for many years. It's pretty much a direct fit for the Miata and uses the same AGM technology which is better and safer for the Miata's battery location in the trunk of the car.
As much as I'd like to continue to buy Westco batteries, I have to be fiscally responsible and ensure that I'm getting the best value for my money. So, I shopped around and found the Marathon battery being sold on Amazon.com by a company called Battery Mart (just search for "miata battery" on Amazon and it will come up). It is an AGM battery and with the exception of the top cap, looks to be pretty much the same battery as the Westco. The part number - 8AMU1R - confirms it. It's the same East-Penn Deka battery as the Westco. The Marathon version was $79.95 plus $23.50 for shipping. The Westco generally sells in the $120 range, before shipping, however I did find a good deal here at $99 and $9.95 for shipping, which puts the Westco only $10 more than the Marathon.

Correct size and the posts on the correct sides for a proper fit in the Miata. This one is going in the '99.

Side-by-side with the Westco, the similarities and slight differences are obvious.

The service from Battery Mart was good. I ordered the battery on Monday and it arrived on Thursday, triple-boxed and well padded.

Just a point in time.

Miata A/C Evaporator Replacement

It's been at least a year since the A/C in the '94 Miata blew cold. It just gradually faded out so I didn't really notice for a long time, until I realized it was really damn hot in the car all the time. I thought for a while that I was going to have to take it to an A/C repair shop, which really goes against my grain. I also knew it would be expensive. At some point, though, I had a revelation. That revelation told me that fixing the A/C was no different from fixing anything else. All I needed was the right tools. A quick check online showed me that spare parts for my '94's A/C system were pretty cheap. I wanted to do it right so I needed the proper tools - a manifold set and a vacuum pump. I already had the manifold set from a previous effort at diagnosing an A/C problem in my old truck, and an appropriate vacuum pump can be purchased at Harbor Freight for around a hundred bucks, which I did.

I'll skip over how I diagnosed the problem, but suffice to say I figured out the problem was the expansion valve. When I went to order a new one for $25, I found that a new evaporator core was only $50, so I ordered one of those, too, just for good measure. Finally, because everyone says you should, I ordered a new receiver/dryer for about $15 and a bag full of o-rings for $3.
This post isn't meant to be a detailed how-to, but it is a "you can". This job was dead easy, except for crawling up under the dash to yank the old evaporator core out. I used this tutorial to guide my actions and it was very applicable to my Miata. The evaporator core is housed in a black plastic box, bolted to the firewall right behind the glove box, with two small 10mm nuts. On the right, it connects to the blower housing. On the left, the center air control unit. Two aluminum pipes stick out through two holes in the firewall, where they connect to some more pipes that go to the compressor and the condensor. I didn't need to mess with either of those things. I disconnected those pipes, unbolted the box, released the clamps that connect the box to the left and the right, and yanked. With a little persuasion, being careful not to damage any aluminum bits, it came out. The evaporator box is held shut with some metal clips that pop right off with a screwdriver, and two screws. The whole thing clams open and you can pull the core right out.

The old and new evap assemblies. After I assembled the expansion valve to the core.

Here's the old core.

Here's the new core with the expansion valve all connected up, set into the lower half of the box. There's a temperature probe that is wrapped to the big tube.  Ok, actually, I don't know what the hell that does. I just connected it up like the old one.

Here's the whole evaporator assembly ready to go back in.  I just had to be careful sticking those aluminum tubes through the firewall, not to jack up the threads.

Here are the connection points just ahead of the firewall in the engine compartment.  They were misaligned quite badly and took some persuasion to get threaded.  Then I initially forgot to tighten the big one down all the way, which became apparent later when I tried to put a vacuum on the system.

Ahh sweet vacuum.  This is what you want to see when you run the vacuum pump. The inside numbers read vacuum in units of inHg (inches of mercury). You run it for about 5 minutes at first. Then you want to stop the pump and wait 10 minutes and hopefully your vacuum doesn't go away. If it does, there's a leak somewhere. I had a big one, but it was easy to find and fix. Then I let the pump run for a good half-hour.

Hard to get it all in the picture but this is how the vacuum pump is hooked up. The blue line is the low pressure side, the red is high, and the yellow line is the line through which you apply vacuum, or feed refrigerant.

Here's where my running pressures ended up after adding 22 ounces of refrigerant and two ounces of oil to the system (I'm banking on there being some old oil left in there). I wanted to see more like 200 psi on the high side, so I may need to add some more R134a, or possibly my compressor isn't strong. We'll see how it cools over the next few days. It felt pretty cold just running it in the garage.

So to sum up, this was an easy project that should make my '94 a lot more comfortable in the Florida summer, which is fast approaching. I commute almost two hours every day now, so having this A/C working is going to be pretty important.

Another iPhone HDR photo