One would think the use of a keyway and dowel pins by now has been accepted as the simplest and most reliable way to secure a pulley or a gear to engine camshafts and crankshafts and to provide marks for timing an engine. That might be an established way to do things, but that is not what you find when you remove the timing and cam cover gaskets from a Mazda MZR engine.

Nope. Those engines use a different method that kind of had me scratching my head. The MZR engine uses no keyways, has flat flanges on the snouts of the crank and cams, and those flanges accommodate a wafer-thin friction washer that keeps the gears tight enough to hold them in place. Those friction washers must be replaced if you remove the gears from the cams or the front pulley from the crank. They can only be used once. The crankshaft pulley bolt and cam bolts also can be used only once.

The 2.5-liter MZR uses friction washers to secure the crank gear and cam gears. They can be used only once. The bolts that hold the crank and cam gears also are one-time-use only.

The friction washers maintain a great deal of torque. The cams get torqued at 50 to 55 foot-pounds, which is not insignificant for a cam pulley. The crank, however, gets torqued to 90 foot-pounds, then turned another 90 degrees. You need a long breaker bar and a strong mechanism to lock the flywheel in place to do this. It’s kind of weird when you’re used to working on the BP engines of the previous-generation Miatas, which use a timing belt and pulleys with keyways and dowel pins.

But the MZR engines were introduced in 2001 in displacements from 1.8 to 2.5 liters, so it would appear the system works. In the North American 2006 MX-5, it displaced 2.0 liters. In the 2017 Ford Fusion, which was the donor car for this NC MX-5 engine swap, the engine measured 2.5 liters in displacement — for which there is no replacement, right?

Mazda stopped development of the engine in 2011 when it introduced its Skyactiv line of engines, but this engine design is still in production to this day, and used in Ford products.

To time the engine, you will need some special tools. You can just Google the words, “MZR timing tools” and find everything you need.

Now, since we didn’t need to remove the cam pulleys, we didn’t use those washers and bolts we bought. Because you do have to use the pulley from the 2.0-liter on the 2.5, you must remove the timing cover and the friction washer on the crank and install a new one. No getting around that.

It’s worth pointing out that because the crank pulley bolt gets torqued to such a high spec, then rotated 90 degrees further, it was difficult to remove the bolt from the older 2.0-liter with more miles and age. We had to soak it for a day in penetrating oil and hit it hard repeatedly with a big impact wrench. It came off the newer 2.5 more easily, but be ready for some difficulty. The flywheel stop is essential for removing and installing the crank pulley bolt.

Remove the crank pulley bolt so you can remove the pulley and the timing cover to replace the crankshaft friction washer.

However, before you remove anything, the simplest way to time the new engine is to bring the 2.5 engine to top-dead center on cylinder No. 1. The simplest way to do that is to pull the spark plug, insert a long zip tie in the cylinder and rotate the crankshaft till zip tie rises to its highest position. When it’s at that point, use the cam position tool to ensure you are at the top of the compression stroke rather than at the top of the exhaust stroke.

The slots in the back of the cams are what time the cams, not the orientation of the gears on the front of the cams. There are no keyways or dowels on these cams. When the engine is at TDC on compression stroke of the No. 1 cylinder, the tool will fit into the slots on the back of the cams.

Essentially, if it’s at the top of the compression stroke, the cam tool will fit into slots on the back of the cams. If it’s at the top of the exhaust stroke, the tool will not fit in. It the cam tool does not fit in the slots, rotate the engine another 360 degrees till the zip tie is at its highest point. The cam tool should slot right into the cams.

The slots in the back of the cams are what time the cams, not the orientation of the gears on the front of the cams. Yeah, it’s kind of weird.

Here’s another look at the tool fitting into the slots on the back of the cams.

Once you have that done, you can take the front of the 2.5 apart so you can remove the timing cover, crank pulley and replace the crankshaft friction washer. Put the new friction washer on the crank and, while you’re in there, replace the crank seal because it’s cheap and easy while the engine is out, and then reinstall the timing cover.

To replace the friction washer, you will need to remove the pulley and the timing cover.

Here’s where those other special locating tools come in. There’s a threaded hole in the passenger side of the block with a 10 mm bolt in it. Remove the bolt and thread in the special tool, which won’t thread in fully if you’re not at TDC on No. 1. But we already did that, so it should go right in.

There’s a threaded hole in the passenger side of the block with a 10 mm bolt in it. Remove the bolt and thread in the special tool, which should go right in if you’re at TDC on the compression stroke on No. 1.

There’s another hole on the crank pulley that has a threaded hole that locates it with the hole in the timing cover below the crankshaft. This hole orients the pulley trigger wheel to the crankshaft position sensor.

Up top, you need to ensure the cam locator tool is still in the slots on the back of the cams. OK, now your engine is in time. Now you need to lock everything down with those torque specs we talked about earlier.

The crankshaft pulley has a bolt hole for the locating tool, which aligns the crankshaft pulley trigger wheel with a hole in the timing cover below the crankshaft. This is what aligns the crankshaft position sensor.

We used the Flyin’ Miata flywheel stop to lock down the flywheel so we could torque the crank bolt to 90 foot-pounds and then dial in an additional 90 degrees on the bolt with the breaker bar. Be sure to remove the special locating tools from each position before you torque the crank bolt.

Here’s a good look at the differences between the 2.5 pulley at right and the 2.0-liter pulley at left. The 2.0-liter only uses one belt, and the trigger wheels are different.

VIDEO

The bolt through the crankshaft pulley locates the pulley so the teeth on the trigger wheel align properly with the crankshaft sensor. The factory spec is to center the sensor on the fifth tooth from the large gap that precedes the first of those five teeth.

Images courtesy of Eric Green and Eric Green

2 COMMENTS

  1. Always a fun idea on paper to swap engines until you find all the little items that go into it, but that old saying of no replacement for displacement comes to mind. Timing cams with slots isn’t an uncommon industry practice and id imagine it’s a cost savings somehow as I remember Chrysler doing it back in the mid 90’s on the new at the time 3.5L v6. The most exotic timing setup procedure I’ve heard of was the Lotus Esprit v8 where the tensioned belt gets strummed and the frequency is checked.

  2. I’ve did many head gasket jobs but they’ve all had markings I started the Mazda and I just made markings my self before I took the timing chains off no though in mind that the crank pulley needed to be aligned also I’ve been looking for days on information and all it needed was the crank bolt loosened and lined with the whole on the timing cover. Before I lined the crank pulley the car would not start due to the crank sensor I tried lots of ways still no start at (all) and now that with your information all I needed was to loosen the crank pulley turn the crank pulley half an inch and line it up then tighten it back down without spinning the motor and everything turned out great!

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