I am in the process of rebuilding my motor, I've read that generally rotor housings are compatible with each other, within the same series. I was planning on using one from an 88 13bt(jspec), and one from an 87 13bt(north american spec).



I am concerned since the leading spark plug holes are not in the same spot. The leading hole for the 87 housing is closer to the trailing hole, while that of the 88 housing is further down away from the trailing plug hole. THey differ in vertical position by about 1 cm.



Will this cause a problem with my motor? If not, which should i pick as the front housing(or does it matter)?



I have the other housing from the 88 motor, but it is not in as good shape as the one I plan on using.

 

i wouldnt mix those housings on the same engine. one spark plug is more "advanced" than the other.

 

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I measured them as follows: the circles in the diagram are the threaded spark plug holes, distance D is measured with vernier calipers.



88 Jspec housing, D = 4.17 cm

87 North american spec housing, D = 3.55 cm



Is it a Jspec thing that makes these different? could someone possibly measure their own 87 or 88 housings? I need to know what would be compatible with these housings now...



Thanks,



Nik

 

I just measured what I'm pretty sure is a 87 uspec housing and I got 35.89mm.



This piques my curiosity now since I thought it was only the 89+ housings where this spacing differs.

 

see, i'm not quite sure about it.



but if it's a japanese 13b-t, then it very much could be the same design as the north american 89+ 13b-t.

the japanese do after all, get japanese cars before we do. take the FD for example. which began sales as a 1991 model car in the japanese market.



on a second note..

i'll tell you honestly that i didn't even know the spacing was different on a series 5 engine.

 

Ok, this seems reasonable to me, so should I start looking for an 89+ housing now?

 

i guess we should both start looking for them.



the only logical reason i can see the how spacing would effect how the engine ran..

i guess looking at it from a mechanical sense, it would mean that the spark to the leading plugs would be retarded in comparison to that of a series 4.



don't take my word for it though, as i haven't had the opportunity to actually build an engine before. i'm just here to learn about it so that when the time comes for me, i'm as prepared as i can be.

 

ive seen a couple of s4 jdm housings, they have n318 cast into them by the metering nozzles, and the leading plug is advanced over the usa housing.



ive never seen an s5 rotor housing with the plug advanced btw, and ive looked too

 

These do indeed have n318 cast into them! So there is no US counterpart that would have this "advanced" plug?



Thats unfortunate since the other n318 housing I have is unusable due to a chip in the chrome, about 1 mm wide and 1 mm deep.

 

If someone has some time, could you please measure the plug distance on an s5 or FD rotor housing? I would really like to know if this housing is compatible with anything available here.





Thanks ahead of time...