Hi;
Ive got a question about the different block series of the 20B, whats the differents between A, B C and D?


Can anyone explain it to me please.

Thank you

 

the castings were stronger starting from A-E..... E being the rarest and strongest housings of the irons.


i've read somewhere on the 20B section that the early build A and B codes could only handle minimal hp gains over stock before certain places cracked

 

"E" Series...Has anyone actually seen one. Not pictures, but actually seen one? I've heard stories that Addkins had two, but has any one really "seen" one?

I've actually heard astute people like Steve Kan and Bob Putman, say that the "E" series are just myths.

 

bob are you talking yourself up again? lol

 

Mazda never did a run of "E-series" engines but they did rebuild plenty of engines after the "D-series" for warranty replacements. You can tell the warranty engines from the black paint on the top edge of the rotor housing were it says Mazda 20B

REgards

 

So the differents between C & D is just harder iron castings for more boost, less friction.

Ok if thats all

 

Is there a difference between C and D series?

D has dowel pins; do A and B have them?

 

All rotary's have dowel pins.

 

Upgraded E-Shaft

 

From the "What 20B# Do You Have?" thread on this forum (https://www.rx7club.com/showthread.p...light=what+20b) :

This is a basic way to understand your 20B engine

000 - 999 = 1st batch
A000-A999= 2nd batch
B000-B999= 3rd batch
C000-C999= 4th batch
D000-D999= 5th batch
E000-E999= 6th batch (only heard of these, never seen one)

I have never heard of an F-series. Since Mazda made just under 4000 20B version Cosmo's I can also picture that the E-series was for warranty replacements if they exist at all.

If the engine has black on the rotor housings & the batch number stamp isn't on there, then its an internal factory rebuilt engine. (meaning its been out in a car & returned after failing within the warranty period)

The last engines to go into a car would have stopped around "D500" for fitment into a Cosmo. For example.........

The last Cosmo sold by Mazda = JCES-100633

However, Mazda quote selling just 369 examples of this series-II version so how it got to #633, I really don't understand.

The latest Cosmo we have ever imported is JCES-100309. Its engine batch # D442 It was a AUG-95 car & production ceased in Sep-95.
If you have any quiries then conact us via http://www.dmrh.com.au


The A series engines were prone to failure because of weak intermediate irons. This was corrected early on in the B series engines.

 

i had #246, it was stamped 246 on all the housings and had black painted "mazda 20b" sections of the rotor housings.

mine was not a rebuild

 

Mine is #756. All housings are stamped. No black paint anywhere. It shows signs of possibly having been rebuilt. I'll know which shaft it has after I open it up.

 

Is there a letter (A-D) in front of the #756? If not, then yours is an original first series engine.

 

No letter. It's an oldie. That's why I've got to open it up to check out the shaft to see whether it's been upgraded because the engine shows signs of possibly having been rebuilt. If it's the old style shaft I won't even bother boosting it. It'll go into a 1st gen NA so it ought to last a long time and make plenty of power in the chassis.

 

whats the difference in the shafts?

 

The later style has a front taper and is stronger where the front rotor journal collar sits.

 

so if i was looking for a reliable 20B, which one would i look for?
or does it just matter how much boost?

 

you want a B,C,or D

The 0 and A series had weaker castings around the factory dowel pins, meaning they break under high boost and/or detonation.

I have broken mine twice at 18-20 PSI (600+WHP) due to wastegate issues. Fortunately, welding technology has progessed to where even cast intermediate irons are repairable. I haven't had any problems with the e-shaft.

Pat

 

You mean about B8XX and up as the early B code motors are small Dowel pin land...

 

awesome thanks!
one more thing,
could someone tell me which thread would be right to ask about buying a 3rd gen RX7 and putting a 20B in it?
i looked around and im confused of which thread to ask that in...

thanks!

 

Pm me with your telephone number and I'll be glad to tell you all about it!

David Hayes