Tuesday, September 6, 2011

Engine - Introduction

The 1.8 liter BP block powered Miatas from 1994 through 2001. I've found that engine resellers generally consider the 1994-97 engines to be "the same". Likewise, the 1999 (there was no 1998) through 2001 are also lumped together. I don't know much about the latter group, except that they are much more complicated mechanically and electronically. Also, the head or at least the valve cover is supposed to be noticeably taller, so it might not fit under the hoods of certain classic sports cars. Besides which the earlier engines are much less expensive and are well-served by aftermarket goodies, which can often be had at lower prices themselves, now.
It is important to note that these 1994-1997 engines are very much *not* the same. Most importantly, the 1994 cars and some, but not all, of the 1995 cars are OBD-I. The later 1995 cars, along with the 1996 and 1997 cars, are OBD-II. The 1996-97 cars change further with the addition of a crank sensor and some other sensor changes. Here is a good overview of the changes to the engine over its history. If you are like me, and buy your parts here and there from various cars as they come available, the lack of interchange can pose a real problem. At the very least, it makes the process take a lot more time.
My engine arrived shortly after my birthday. Although I had ordered a 1996-97, I got a 1994. This peeved me, as I really wanted OBD-II. Also, the engine was from an automatic, and not a manual, so the compression is lower and I would have to buy a flywheel. Like most engine resellers the one I used insisted that all Miata BP long blocks are the same. Also, did I mentioned that the engine was damaged when it arrived? And I was up-charged $300 shipping? Don't order your engine from these people.
The biggest problem with getting an earlier engine is that I had already bought an ECU and several harnesses for a 1996-97 car. Since 1.8 liter Miatas are not very frequently intact when they appear in the So-Cal salvage yards, it had taken me about 6 months to get these parts. Worse, I had passed by '94 ECUs along the way. Frustrating when you have little patience and less money, but after a few more months of looking and a couple bad eBay purchases, I got what I needed from the salvage division of Flyin' Miata. A great resource.
I will say it here, and say it again in the Electrical section, you should really buy a whole Miata or a front clip or whatever it takes to provide yourself with an engine, transmission, harnesses and ECU that all fit together. It takes a whole lot more time, and more money, to pull together all the bits and pieces, and the variation among those bits and pieces is surprising and enough to make things not work.
Nevertheless, here are two sources for rebuilt Miata engines that I came across:
-"Precision Rebuilt Engines" has rebuilt 1.8L Miata engines, long block, for $1520. They are located in Houston, Texas.
-"Best Rebuilt Engines" allows you to specify which 1.8L engine you are getting (e.g. the 3/95-11/97 with sensor on oil pump) from $2544

The engine arrived on this pickup and we hoisted it out with my 2-ton hoist and some 1000-pound rated climbing rope from an army surplus store. That rope is handy stuff.
Quick and dirty stands cut from 3/4" plywood I had found in the alley behind my house in the morning before my engine arrived. Later I added 2x4s along the bottom edge because that thin tongue in the back had to take a lot of weight once I bolted the transmission on. Very solid stand, though, at a decent height, for working, for free.
The test fit looks really good. But, this is just the engine. Everything changed once I bolted on the transmission and tried to center and level the drivetrain. Thus began the era of hacksawing bits and pieces off. It's most serious for the transmission, but what follows is what I cut off the engine.

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