Hey all,

I've been searching low and high for information on Mazda's warranty motors to no avail.

I understand that the black paint on the branding section of the rotor housings (where it says Mazda 20B) suggests the motor was a factory rebuild, as well as the lack of engine number stamps on the rotor housings.

What I wanted to know was whether anyone had any insight into whether there was a standard rebuild method, or if it varied from engine to engine.

In the case of an A series engine I have seen, that appears to have gone through this process, is it likely to have a late model eccentric shaft, or other updates, or were these just rebuilt using factory internals?

I understand this could potentially be a difficult question to answer.

 

Black on the housings doesn't mean anything, no numbers is considered a factory rebuild.
It would be worth checking over the rest of your engine for any other numbers (not just housings)
Checking for the engine number on the plates may help to have some insight as to factory rebuild protocol. checking from the outside of the engine look at the rear plate and see if it has the larger bossing.

 

The motor is being torn down for a full build with porting and stud job regardless, but wasn't sure if there was standard practice within Mazda for these builds.

Numbers on end plates were A532, but housings didn't have any. I awaiting the arrival of the motor from Japan, as I buy every 20B I have access to on the ground over there.

Will have a good look at it all once I have it in my hands.

 

Well if its coming down proof will be in/on the shaft.

 

as you probably know, an original engine would have stamps on all the housings, rotor and side. new parts are not stamped with the number. so if the irons match, but no stamp on the rotor housings, that means the rotor housings were replaced with new ones. the Eshaft should be stamped with some kind of marking too, although figuring out what the marking means may not be obvious.

i actually wonder if Mazda rebuilt engines, or just replaced with a completely new one, as i'm not aware of them ever rebuilding an engine, nor is there a part number for one (although there might have been a bulletin or something, and we wouldn't have that). we checked and they did have new 20B blocks as late as, i think 2010, but they were $$.

possible the rumor comes from the cosmo shop manual and parts manual, not having the engine section, so the dealerships couldn't rebuild it even if they wanted.

 

Yeah I'm assuming it had new housings at a minimum, but will be interesting to see once it's all opened up.

The motor will be far from stock so either way there should be no issues with it once I'm done. This was more a question out of curiosity than anything.