My engine rebuild is progressing well after I got past the front eccentric shaft bolt epic. Now that everything is taken apart and is somewhat clean I am looking for some opinions on a couple questionable parts. All of the housings and rotors checked out alright since they are within Mazda specifications. However, the eccentric shaft is a little out of spec (.0005" - .001" too much oil clearance). From the pictures you can clearly see the failed front and rear main bearings.

Since Mazda sells variable sizes of main bearings, is it possible to compensate for the slightly out-of-spec eccentric shaft or is this one junk?

Even if it is possible, I am a little worried about the condition of the shaft. There appears to be some blue bands apparently caused by overheating? I thought this was the case except every used eccentric shaft I find online has the same banding.

Entire Eccentric Shaft

Rear Journal Surface

Front Journal Surface

Center of Eccentric Shaft


Most likely the missing chunks of bearing came out during dissasembly. The engine was sitting for about 9 months and was locked up when it was pulled out. It broke loose during the removal of the rear eccentric shaft nut.

Failed Front Main Bearing

Failed Rear Main Bearing

 

How much can another shaft cost ,used ? Someone will sell you one, I may even have one to sell . Do not use one that has been overheated or undersized .I have not seen your pictures but read the text .

 

A over heated (burnt) e-shaft will fail very quickly. Maybe 100 miles. The flaw will start near the banding and progress from there. You then can expect SEVERE progressive damage.

That engine was abused. The shaft may be ready to go south at any moment...

Don't confuse the heat treatment with the surface journal damage. The heat treat is normal, and required for the crank to have strength. When it is manufactured, the journal is electrically heated and then rapidly quenched in a special bath. This casehardens the journal to between 0.050" and 0.100" deep to somewhere around 50 Rc. In a crank's operating all the stress is concentrated near the surface, so harnening makes the metal stronger there.

Cracks, scratches, and impacts weaken the e-shaft, but not nearly as bad as re-heating. The smoked journal cools very slowly in the engine causing it to be anealed. The strength will drop in half or less. Some will suggest to grind the shaft...not a good idea. Grinding reduces strength, although there is margin to do so on a good crank. Keep in mind though that the heat damage goes deeper than the casehardness. In this case, a bad idea.

Call Kevin Landers and get an eshaft from him. The price will be right and the shaft good.