Archive for March, 2013

1994 Mazda Miata Engine Rebuild – Part 2

Well, in my previous post I wrote about some interesting cylinder marks on the #2 and #3 cylinders. Today I measured the head and found .033″ runout on the plane. I was so surprised, I literally measured it 9 times. The tolerance is .004″

After accepting that it was badly warped, I decided to do a more thorough inspection, and quickly found these little treats on the #2 and #3 cylinders:

 

#2 head crack

#2 head crack

#3 head crack

#3 head crack

So that explains it. #3 had the worse looking cylinder, and also the bigger crack.

For what it’s worth, I was never expecting to find this in my engine. The car burned oil, but it’s well documented that these engines seize their oil control rings. It never used any coolant as long as I’ve had it, and thought I was just going in for some routine (every ~150,000mi) maintenance.

Boy was I wrong.

Well, I guess I’m in the market for a new head, and seriously considering getting some more extensive work on the bottom end. I was content with just deglazing the cylinders, but now I know that the engine has had some bigger issues in the past (probably overheating) and it makes me much more suspect about the bottom end.

 

1994 Mazda Miata Engine Rebuild

 

For starters, these are just pictures of some weird issues in Cylinders #2 and #3 that I’ve never seen before. Photos of Cylinder #1 provided for reference.

 

1994 Mazda Miata engine with 180,000mi. Rebuild due to burning lots of oil. Found the oil rings on all four pistons to be seized.

I may update this post in the future with more info/pictures to make it a real post, rather than just a placeholder to share images.

 

Good looking cylinder #1

Good looking cylinder #1

Another angle of Cylinder #1

Another angle of Cylinder #1

 

Cylinders 2, 3, and 4.

Cylinders 2, 3, and 4.

 

 

Close up of cylinder #3

Close up of cylinder #3

Different angle of Cylinder #3, showing marks in sidewall

Different angle of Cylinder #3, showing marks in sidewall

 

Closeup of mirror-like finish in cylinder #1

Closeup of mirror-like finish in cylinder #1

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