NA8 and NB8A Engine Question

forcedfive · Postby **forcedfive** » Sat Apr 25, 2015 11:17 am

Hi All,

Can anyone confirm if the block and crank from teh Na8 engine are the same as the nb8a block and crank?

Would anyone happen to have a NB8A crank lying around that they would like to sell?

Cheers

93_Clubman · Postby **93_Clubman** » Sat Apr 25, 2015 12:52 pm

http://www.solomiata.com/BP8.php
http://www.solomiata.com/Mx5Engine.html

forcedfive · Postby **forcedfive** » Thu Apr 30, 2015 2:25 pm

Thanks for the link. Not 100% sure from the info though that i am able to interchange a 1.8 NA short motore with the NB8A, Can anoyone confirm from personal experience.

slug_dub · Postby **slug_dub** » Thu Apr 30, 2015 4:46 pm

Pretty sure you can but you'll be dropping .5 compression ratio... NA B: is 9.0:1 and NB8A is 9.5:1 I thought?

forcedfive · Postby **forcedfive** » Thu Apr 30, 2015 5:29 pm

Thanks Slug. Compression is fortunately not a concern for my needs.

manga_blue · Postby **manga_blue** » Thu Apr 30, 2015 5:48 pm

I dropped an NB8B crank and rods straight into my NA8 block after a longnose failure on the original crank. I had them side by side and measured them up - they were identical. I couldn't imagine the NB8A crank being any different.

manga_blue · Postby **manga_blue** » Thu Apr 30, 2015 5:55 pm

Mazda crank part numbers:
NA8: BP06-11-300C
NB8A: BP06-11-300C up to 0522
NB8A: BP06-11-300D after 0522
NB8B: BP06-11-300D

forcedfive · Postby **forcedfive** » Thu Apr 30, 2015 6:55 pm

Thanks Magna Blue

I have heard there are issues with the NA8 cranks and your expeience seems to support that. Any else know of issues with NA8 cranks?

manga_blue · Postby **manga_blue** » Thu Apr 30, 2015 10:49 pm

It doesn't support that. My experience is that some dodgy mechanic put a crank pulley on badly during a timing belt change job. The crank nose started to fail after that, just as it could with any BP nose. I've never heard of anything inherently wrong with any of the cranks other than that.