Friday, April 11, 2014

Everything you never wanted to know about Miata oil pumps

I recently got a crash course in Miata oil pumps.  Since I haven't seen a good write up anywhere that would have helped me avoid the need to learn about this, I figured I'd pass it along hoping it helps someone.

There have been 5 oil pumps over the Miata's lifecycle.
1. The oil pump for the Short Nose Crank 1.6 motor in cars from 1990 to early/mid-1991.  Here is a page from the Factory Service Manual illustrating installation.

2. The oil pump for the Big Nose Crank 1.6 motor in cars from 1991 to 1993.  The difference between this and #1 is that the diameter of the hole for the crankshaft is larger to fit over the snout of the BNC motor crankshaft.  Because of the larger hole for the larger crankshaft, the oil seal is larger diameter also.  Both of these oil pump attach to the engine block using a paper gasket.
Here is a pic from the Factory Service Manual showing how the 91-93 oil pump mounts.

3. The oil pump for the NA chassis 1.8 motor in cars from 1994-1997.  This looks the same as the 1.6 BNC oil pump but the design on the rear of the oil pump changed in 2 ways:
3.1. The mountain face of the oil pump where it mates to the engine block has channels machined into it and now uses RTV sealant instead of a gasket - like the oil pan.
3.2. The outlet of the oil pump where it meets the oil channel in the engine block takes an o-ring.
Here is a comparison of the 1.6 vs 1.8:
Note: I 'borrowed' these pics from these threads:

Here is the parts diagram from the Factory Service Manual for this oil pump.  Notice the difference...

4. The oil pump for the NB chassis cars from 1999-2000.  This is a different part number compared to others and has been superceded with the newer oil pump.

5. The oil pump for the NB2 chassis cars from 2001-2005.  In 2001, with the addition of VVT, Mazda changed to an oil pump with a slightly higher volume.  This oil pump is slightly thicker gears and corresponding case to fit the gears.  This oil pump also takes an o-ring and uses RTV instead of a gasket.

Here is the kicker, this later pump is also about $100 cheaper than the 1.6 oil pump...  Compare prices here for yourself:

I bought the 1.6 BNC oil pump from Mazda Motorsports for ~$250.  Had I known, I would have saved myself $100 and bought the later pump.  Fun stuff...

Sunday, March 30, 2014

More engine rebuild complications - Miata Piston Rings

I recently ran into another set-back.  Some friends were over to help me with the assembly.  The plan was to install the piston rings onto the pistons and then install the crank and pistons.  The plan quickly went to hell...

If you, like me, have never assembled an engine before or handled a piston, you would have never thought that those little dinky piston rings are engineered for a very specific orientation on the piston.  Let's review using this naked piston as a reference.

The bottom most set of rings are the oil control rings.  As I understand it, the purpose of the oil control rings is to retain a little bit of oil to lubricate the piston to cylinder wall during the up and down stroke.  This bottom most ring is actually 3 pieces.

The second or middle ring is the 'scraper'.  It scrapes the side of the cylinder of oil to keep it out of the combustion chamber - the semi-circular, bowl shaped area between the top of the piston and the bottom of the valves.  It is OK for oil to be present in the cylinders up to this point but not above.  If oil makes it to the combustion chamber that means that the piston rings are sealing properly, results in low compression and the oil dilutes the combustion and results in blue smoke out the exhaust.

The top or first ring is the compression ring.  It is responsible for compressing the air from the intake manifold with the fuel being injected from the fuel injectors while the spark plug ignites the mixture and creates the big boom that forces the piston back down the cylinder and makes the engine run.

The original Miata Factory Service Manual published in the early '90s provides information on how to install the piston rings.  The oil control rings don't have an up or down orientation but they do have to be 'clocked' in a certain fashion for purposes that I don't really care to learn...  The second/middle ring does have a top and bottom.  This one is easy to figure out which was is up just by looking at it.  The top/first ring is a fucking bitch.  That's a technical term...

The image below is from the FSM published in the early 1990s.  I state the publishing date for a reason.  A reason that cost me a week of time in this build...  This early version of the FSM states that the top ring is marked with a letter 'R'.  Guess what?  Things have changed since the 1.6L Miata engine was first manufactured and this version of the book was published.  The new piston rings that I sourced from Mazda Motorsports do not have the same markings as they used to.  The top / first piston ring can now either be marked with an R, marked with a dot, have a bevel on the edge that is supposed to be oriented upwards or it could have no frickin' marking at all.  A more recent publication of the Hayes manual (which I don't have) states that the top / first ring will be marked with a dot.  That still doesn't help since mine don't have a dot...  Hmmm...

Since I bought my parts from the good guys at Mazda Motorsports, I called them to get insight and learned that the version of the FSM I was using had been updated.  They emailed me the most recent version of the FSM which states the following with regards to piston ring orientation.  Pay attention to #2...
Yeah...  Great....  Where's that face palm meme?  That would fit well here...

Thankfully, I got this sorted but lost a week which means delays when I can get started racing again.  I'm enjoying the engine build but tripping over this was annoying.  Regardless, thanks to friendly Miata people posting on and the guys at Mazda Motorsports, this mystery was solved.

The oddest part is that we couldn't even see a bevel or taper in the top / first piston ring.  3 of us tried to find some sort of mark that would distinguish which was was up or down but we couldn't.  The top set of rings did have one obvious visual marking - a white paint dot - but no mention of how this paint mark relates to orientation can be found anywhere.  The only time I was able to visually see the beveled /tapered edge on the inside of the first ring was when I stacked a couple of rings together and held them over a white background like in the picture below.  If you look close enough, it looks like there may even be a smaller bevel on the bottom side of the piston ring also.  Either way, I wound up installing the top ring with the white mark on the right - which placed what I thought was the most noticeable beveled / tapered side upward.

With this mystery sorted, I was finally able to start assembly and I made great progress!  I'll make another post on that in the next couple of days.  Hope this helps someone else out in the future.

Sunday, March 9, 2014

Testing and Cleaning the Miata's Fuel Injectors

Since the engine is apart, now would be a great time to send out the fuel injectors to get tested and cleaned.  Lots of places to choose from including:

Normally, I would have used Advanced Autosports since I get many of my race parts from them but I forgot they offered fuel injection services so I sent them to RC Engineering.  I mis-placed the fuel injectors from the core 180k mile engine during my move so I removed the fuel injectors from the '91 engine that was in the car with 91k miles.

I was surprised at the test results!  2 injectors were dripping.  Dripping is not good for power.  The other 2 injectors were better but not great.  Never would have expected dripping injectors at 91k miles.  The previous owner of that motor must have neglected fuel filter changes and gotten some gunk through the fuel filter and into the injectors causing the 'dripping' condition.  Glad I got this done.  $107 well spent I think.

You may want to consider sending your injectors out for servicing if you haven't.

Cleaning, cleaning, cleaning engine parts for the rebuild

Well, since I won't have time or budget to make the first two races of the season, I've lost some of my motivation in getting this rebuild done quickly.  So I slacked off this weekend and did other things - like have fun.  I did spend some time in the garage today cleaning some ancillary parts and checking to see if I'm missing any parts for the rebuild.

Cleaning the Throttle Body and Intake Manifold

A clean intake is a good thing.  Might as well do it since the engine is apart.  Better airflow, cleaner air = reliable power.  This really took a lot longer than I expected to get the internals of these parts clean.  Lots of nooks and crannies that you need to get into with engine block cleaning brushes.  

I started with the intake manifold and throttle body.  I started by removing the electricals.  Marked which clips belonged to which injector and removed the fuel injector harness:
Next, removed the throttle body from the intake manifold.  I don't think it had ever been removed before.  It took some effort to separate the throttle body from the intake manifold.  I realized I will need a throttle body gasket since it fell apart during dis-assembly. :(  Both the throttle body and intake manifold were pretty nasty and gunky inside.  Yuk!  You can't really see inside the intake manifold in this pic but it was just as nasty (if not worse than the rear of the throttle body you see in the pic.
Here is an attempt to view in the intake manifold.  Looks nasty in the pic.  It was just as nasty in real life.

Decided to start with the throttle body.  I busted out the carb cleaner and brass wire brushes and got busy on the throttle body.  Here is a during shot.
Almost done here.  Spent a ton of time with the wire and nylon brushes getting all the nooks and crannies of the throttle body clean.  Lots of gunk in there.  More than I expected considering this throttle body came from a car with only 91k miles.  Final step - trying to remove the frickin' gasket.  This thing was hard as rock.  The razor blade was the key to getting it off.

Next, moved onto cleaning the intake manifold.  I ran out of carb cleaner so I used the mineral spirits and wire brushes on it.  Turned out OK.

Inside view of the intake port.  Nice and clean now. :)

View from the throttle body opening after scrubbing with mineral spirits and long handled wire brushes.  Going to get some more carb cleaner and give it another cleaning with some nice caustic car cleaner since I have the time.

Cleaning Ancillary Parts

This is far less important than the throttle body and intake manifold but I had some time to kill and wanted to do something brainless so I cleaned up the water outlet, head-to-block bolts, piston squirters, coolant hard lines and other bits and bobs.  Pics!

Lots of work.  Some with little value but I like clean engines so I'm happy with the time spent since I have some time to kill right now.

Sunday, March 2, 2014

Miata Engine Rebuild Complications....

So...  Turns out the original 'short nose' crank that was on this motor is damaged. I discovered this when I was test fitting a new woodruff key and timing cog that I had ordered from Mazda Motorsports.  I ordered a bunch of parts and a rebuild kit from them.

Remember from my earlier post where I had a difficult time removing the timing cog from the crank?  I should have taken that as a sign that the keyway in the 'short nose' crank was damaged.  Actually, it was the second sign.  The first sign was that the large 21 mm bolt that holds the timing cog and pulley on the end of the crank was hand tight.  That bolt should have around 100 ft/lbs of torque holding it on so for it to be hand tight is a bad sign.  When that bolt is loose, the woodruff key, pulley and timing cog are not properly attached and causes the pulleys to wobble. is full of threads on the issue and YouTube has various videos on the topic.

The machine shop must have missed the issue with the keyway when they were checking the crank over.  Here is a pic of the issue.  This keyway is no where near as bad as some of the horror stories you see on the forums.  I could fit a .229 mm feeler between the woodruff key and keyway.

I briefly considered the 'Loctite Fix' that you read about on but after researching it further and getting input from people, it is more of as a repair to get you by for a while and can fail again.  Since the motor was apart, there was no point in putting it back together with a damaged part.  Especially on a race car.  I decided to get a replacement 'big nose' crank.  Click to research Miata crankshafts.

I decided to pull the running 'big nose' crank motor that was in the car so that I could use the crank from that engine.  So I invited a few friends / Spec Miata competitors over and we pulled the motor last Saturday afternoon.  Yes, competitors in my region are also friends!  The racing community is very supportive of its members.  Victory Machine graciously offered to clean and prep the new crank without charge so I dropped it off.  It turned out great.

So I now have all the parts that I need to assemble and rebuild the engine.  I spent a lot of time with carb cleaner and engine cleaning brushes cleaning up all the oil and coolant passages and chasing the threads all over the block in preparation for assembly.  Time to get busy bolting it together and testing clearances with Plastigage.  Should be a learning experience.

Monday, February 17, 2014

Machine work for the Spec Miata 1.6 engine rebuild

Having never had need for a machine shop before, I asked around to various local Miata enthusiasts to find a trustworthy machine shop.  I also checked Yelp and Google'd to find reviews on different forums.  I discovered that some shops only work on American cars.  Long story short, I settled on Victory Machine in San Jose mostly due to Yelp reviews and proximity.  Proximity b/c work and life is getting busy again so I don't have time to drive an hour away to shops some recommended shops.

Originally, I had wanted to measure the parts myself but after doing more research, I decided not to.  Turns out that accurate set of measuring devices are very expensive.  It would have cost me about $500 or more to buy the tools to measure this stuff myself.  I watched some videos with guys using cheaper tools to measure and the steps they had to take to find the level of inaccuracy and take that into account with each measurement.  That would drive me fucking nuts.  After speaking with Victory Machine, I decided I'd just pay a professional with the proper tools to do that part.

I drove over to Victory and spoke with the owner about my plans for a budget rebuild.  Turns out that they have done Miata engines before for other racers that I apparently haven't yet met.  He educated me about different options and suggested some base work to clean the parts (hot tank) and measure everything to ensure all the hard parts (block, pistons, crankshaft, head) were re-usable.  Much easier and faster than me attempting to do this.  More accurate too.  Pricing was acceptable also.

Machine shops typically start by hot tanking the engine block and parts to get all the dirty, carbon and oil off the parts so that they can be accurately measured.  Next they measure everything and compare to factory specs.  From there, they know what parts can be re-used and what parts cannot be re-used.  Once they figure out what parts are going to be used, everything gets thoroughly cleaned again and assembled.

A week later, I had some shiny engine parts :)  I'll get some pics up soon.

I had originally wanted to rebuild the head myself along with the bottom end but the technician started rebuilding the head accidentally.  Their pricing was fair so I had them finish it.  The bottom of the head was resurfaced, valves were cleaned and refinished and everything was assembled.

All together, machine costs with the head rebuild totaled around $800.  Not a bad deal but more than I had planned on spending.

Now I need to clean out the oil passages in the block and crank to get it ready for assembly.  As mentioned above, this finish cleaning is always necessary after machine work.  Next post will deal with cleaning.

Saturday, January 25, 2014

My Spec Miata 1.6 Engine Rebuild has begun!


I last posted about this in July.  Shortly thereafter, work got busy, summer happened, bought a house, moved, did some house renovations and I'm finally getting started on this project.

I started this project with a lot of research.  I'm fairly handy with a wrench but I've never opened a motor before so I educated myself about the rebuild process.  I'll make another blog post with helpful videos, posts, pictures and books and such that I used to educate myself but for now I'll focus on my progress.  While wrenching, I mostly refer to the Miata Factory Service Manual (aka FSM) and the Miata Enthusiasts Manual.

I bought an engine stand from Harbor Freight for $65 and got the engine situated using my engine hoist.  Also cleared some space in the garage so that I can work on this.  Here is my work space:
Following the FSM and the Enthusiasts Manual, I removed all the stuff on the front of the engine, the valve cover, head and oil pan.  All of this was easy as it was pretty detailed in the books and it is honestly pretty obvious how to get these parts off.  Progress was quick.  I made an effort to take pics of everything so that I could reference the pictures when putting the engine back together again.  I also tried to mark parts so that I could re-install them in the same position that I removed them from.
The camshaft journals are marked so didn't need to do anything here.
Cams off:
With the cam removed, the HLAs come off by hand.  I almost lost them when I started rotating the engine.  I got an egg crate and labeled the location that I removed them from.  
The cam journals look pretty rough.  The markings you see here don't feel rough or scratched up.  I'll need to revisit this later.  Right now I'm focused on rebuilding the bottom end.
Engine pan off.  Easy peazy.
Some minor gunk (oil pan sealant?) in the oil pickup but mostly clean beyond that.
Head is off.  
This is why you should you DISTILLED water in your coolant system and NOT tap water!  Those are mineral deposits from minerals in tap water from the previous owner's mechanic. :(  The cooling passages also have this crap.
Pistons look OK from the top.  Carbon deposits on the top of the pistons.  You can see more gunk in the coolant passages too.
View of the underside.

Removing the timing cog on a SNC 1.6 Miata 

I was making great progress until I got to the timing belt cog.  It wouldn't budge.  I spent a good long time Googling about how to remove this bitch of a part and tried everything I read.  Some people suggested 3 prong gear pullers.  Tried a few different ones and they didn't work.  The FSM says that the proper tool is a steering wheel/gear puller.  I tried that too but the bolts included in the kit do not fit the threads in the timing cog.  I wasn't sure what I was going to do about this....

I wound up posting about my issue on the local Miata club forum (Bay Area Miata Drivers).  Thankfully, a fellow club member (and total stranger) from the local Miata club offered to lend me a tool he fabricated for this job.  So he mailed it over and long story short - it worked.

Here is the custom tool I used to remove the timing cog on the SNC 1.6 Miata.  I used the screw driver just to keep the crank from turning.  The timing cog fought me the whole length of the crank shaft but it did eventually come off.  Of course I broke it in the process while trying to manhandle / pry the damn thing off but I didn't plan on re-using it anyway.  I could now continue to dis-assembling the bottom end.
Pretty rusty and gunky as you can see:
Here is is cleaned up and dried off from it's bath of penetrating liquid.  The keyway looks in good shape so I can re-use this crank.

Dis-assembly of the bottom end

Things progressed quickly from here.  Following the dis-assembly procedure of the FSM, I removed the oil pump / front cover.

Then the rear cover:

Measuring engine clearances

Time to start measuring.  The FSM and Enthusiast manual both suggested measuring clearances before tear down.  I figured it would be a good idea also so that I can compare clearances when I assemble.  

I bought a feeler gauge and checked the clearances on the Connecting Rods and wrote down the measurements.  I had never done this before.  I had expected that the connecting rods would have a fixed position on the crank.  Turns out they move front and back along the crank shaft so as I inserted feeler gauges into the gaps, the connecting rod would move slightly allowing me to progressively insert larger feelers until such a point as the maximum range of the factory tolerances was met.  It actually took me a while to figure out what was happening so pay attention when you do it.  Turns out my clearances were within spec.  Goodie! :)
The FSM also said to use Plastigauge to check oil clearances on the connecting rods and main caps.  I was tempted to but I didn't have any and was making such good progress that I decided to skip that step and complete the dis-assembly.  I marked the connecting rods using a punch as the Enthusiast Manual suggested so that I could be sure to use that same piston and rod in the same cylinder.  I noticed that the main caps had unique numbering so I noted these numbers in my note book.  The FSM and Enthusiast Manual specifically state to NOT attempt to punch these caps so take note.

Eventually, we ended up with a bare block.  Well almost.  I removed the oil piston squirters later.

The cylinder walls all looked good.  There were no ridges at the top of the cylinder bores.  The cylinder bores felt pretty smooth.  I'm going to send this out to the machine shop to clean up and measure the bores with their super accurate and expensive bore gauges and then figure out what parts I need to buy.

I need to have a good look at the pistons and the bearings.  I'll post more about those in another post.

Thanks for following along.  Let me know if you have any questions or advice.

Friday, January 3, 2014

Comparing thermostats - Mazda OEM vs NAPA

I took a bunch of pics and measurements of various thermostats when I was testing them on my Miata.  I thought I would share them in case you are curious.  I compared and measured them looking for differences to substantiate why the OEM might be 'better' as some people say but could not notice any difference in materials using my naked eye or primitive measuring tools.  Even the spring feel similar when compressed using my hands for force.   Not very scientific but good enough to establish that the NAPA stuff is not made of weak springs or materials that are flimsy.

First, let me start by saying that I only compared the OEM Mazda thermostat with the NAPA sourced thermostats.  The Miata uses a generic, common sized thermostat with a 52mm / 2 1/16" diameter.  NAPA was the only parts store that would give me a hard time when I ask for a generic 2 1/16" thermostat in 180* or 160*.  Every other part store would only look up the Miata and sell me whatever the stupid system said was the one.  Just walk into NAPA and ask for a generic thermostat in 2 1/16" and 180* temp with the part/reference number of 142 and they should be willing to help you.

Here is a pic comparing the OEM thermostat with the 180* #142 Napa thermostat.  The NAPA is shorter but it makes no difference as it fits the thermostat housing / water outlet housing perfectly.

Here is a pic of the inside of the thermostat housing (aka water outlet housing as the part's store books refer to it...).  The thermostat can be shorter and still fit.  However, it cannot be longer / taller the the OE and fit.

Here is a pic [attempting to] measuring the size of the hole that the water circulates through when the thermostat opens in NAPA vs OE.  I couldn't find my calipers so I used a tape measure - sorry.  The diameter of the hole is very similar.  Perhaps only a mm larger in the NAPA.  Napa on the left.  OE on the right.

OEM thermostat:

Hope that was interesting in some way.