Track Dog Racing

Loctite Fix for the early (1990-1991) Miata Engine

Diagnosis

A. Verify it's a short crank.


The short crank engine uses a four slot pulley. Count the slots in your pully. If
it has eight slots, it is not a short crank engine. While all engines can fail if the
crank bolt gets loose, the short crankers are more likely to fail.

 

B. Is it really slow?.


Drive another miata and compare. If your car feels much slower, there could be an issue.

 

C. Does the pulley wobble?


It's pretty subjective, but when the bolt is really loose, the pulley will seem to wobble. Compare it to another pulley, such as the water pump, power steering, or AC pulley.

.
 

D. TDC Check

When the piston is at top dead center (TDC), it will be at the top of its stroke. If thekeyway is not damaged, the timing mark on the crankshaft pulley will line up with the timing scale next to it.

If one removes all the spark plugs, the engine can be rotated to TDC by putting a long rod down the first spark plug hole and "feeling" when TDC is reached.

You will need a 21mm socket on the crank bolt and a suitable wrench. Only rotate clockwise.The Mazda Shop Manual says never rotate counterclockwise.

You may have to remove the intake tubing to get room to turn a wrench here.

 

 

Here's what I saw on my car. The #1 piston is at TDC. The timing mark is about
16 degrees before that. It corresponded to the wear in the crankshaft keyway when I took it apart..

Too bad, no?

 

 

 

 

F. Remove Bolt and look

 

I've never done it, but have read it's also possible just to remove only the bolt. Then with a mirror, or digital camera, do a visual inspection. A good one looks like this.

 

 

 

 

 

 


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