I went to look at a 20b yesterday and I can't seem to find any codes on either the housing or the irons. I'm guessing this is a pre-code one and not for me. I took some pictures but they didn't come out that great...








thewird

 

none of the pics are really of the right spots... generally on the rotor housings the number is stamped next to the 20B. on the irons its more toward the top.

remember they started with 1 and ended somewhere in the E's (i think, its been a while, actually last time i checked they still had new shortblocks available in japan).

since new 20B parts aren't stamped, an engine with no stamps means that housings were replaced.

examples.

i had engine #246, so there was a 246 in all 7 housings. i was lucky enough to get a fairly complete engine, so not only was it "numbers matching" but it didn't look like the airfilter or the oil had ever been changed either.

my friend has an engine, i forget the numbers, but it has a mix of a few different numbers, and some housings have the original number scratched out, so its been rebuilt, from at least two cores.

we also have a few new housings in boxes and these have no number stamp, so we could build an engine with no numbers, from new parts.

i'm not really an expert with the 3 rotors, but i've done a few swaps, and tripped over 20B parts cause they are all over the shop for years

 

So there was no generation of engines that had no codes? Any other way to identify it? Aside from taking it apart?

thewird

 

The engine has to be stamped.. Look in the correct places..

Your pictures are not great...If I had to guess, I would say its not a C or D code..

 

What are the other places to look at? I know my pictures are terrible. I realized that after I got home so I dont have any others. This one was a picture of the rear iron though as that is the only one i could easily see and there was no code. I could go look at it again but I'd have to know where else to look or what to look for.



thewird

 

there were 'pre A' code engines. early generation before they started labeling a b c etc.. so if you had 246 then it was an early production pre a code engine. pre a, a and b had some minor differences from c d and fabled e code engines. its my understanding that the later generation ones are the more desirable engines if you are looking to make a lot of power.

 

So every 20b ever built by Mazda should have a number somewhere whether it has a letter or not? Unless it was rebuilt in which case some housing may not have a number? Is it at all possible for their to be no numbers at all?

thewird

 

1st year: No letter stamp, only a 3 digit # (000-999)
2nd year: A code stamp and 3 digit # ( A00- A999)
3rd year: B code stamp and 3 digit # (B000-B999)
4th and 5th year: C code/ D code and 3 digit # (C000-C999/D000-D999)

 

^ Yah, I know that. I just wasn't sure if there was a generation with no numbers at all.

thewird

 

All of them are stamped..

Easiest place to see it is on the rotor housings.. but some engines failed and where overhauled by Mazda Japan under warranty. Those engines usually dont have the stamp/ stamps on the rotor housings, or it was machined off. The plates would still be stamped, unless those would have been replaced too

Very unlikely to have had an engine overhauled where all the plates and housings were replaced..

Cant find #'s anywhere... then...

Just look and the dowel pin lands where they meet the rotor housings..

If the sildeplates are taller than the rotor housings ( like FD engines) where they meet, then it has the 4mm larger dowel pin land side plates that you are/seem to be looking for..

Yet none of this matters if you plan to make big HP and run alot of boost. C/D code engine can still break the dowel pin lands on the sideplates. All of the engines can break in the same spot, on the thick center plate ( hardest to get and most exspensive ) when makes upwards of 600hp.

Plan on making BIG HP? Then plan on buying a 12.7mm stud kit and doing the required machine work on the block.

Problem solved..

 

yes. the only way to have no numbers would be to buy all the parts and assemble it yourself

 

Thank you Japan2LA. My concern about needing a later series 20b is for the bigger dowels & strengthened e-shaft. I do plan on studding it regardless of what engine I get. So your saying if I stud it, it doesn't matter if I have the bigger dowels? Do you know when they upgraded the shaft?

My goal is to make a reliable 600+ rwhp setup for the circuit but be capable of 800+ rwhp at high boost for the street (or really just because).

thewird

 

The stampings will be next to the "20B" on the housings, near the pocket on the rear iron, on the lift ear on the front iron, halfway up on the intermediates. On this engine pictured, 2 rotor housings and the thin intermediate were replaced so there are no stampings. The C & D engines have all the updated parts.

 

Here is an A series we just tore down for rebuild that the markings are a little easier to see

 

Awesome Banzai, thats what I needed to see where all the codes should be. Thank you.

thewird

 

I have limited knowledge about the 20b, and are wanting to know about the different type's between the 20b's A,B,C... ect and which series is best and why please?

any new housings ect, what model are they based off?

any info would be much appreciated, thank you.

 

C and D is the best series because it has the upgraded dowels on the irons for better strength similiar to the FD size. It also includes all the fixes from previous series like stronger e-shaft and extra 12mm tension bolts.

thewird