Ok so I’ve done quite a bit of research on this topic. Both here and on d-series and I’ve noticed that none of the post have a definitive answer. I have found lots of conflicting information and would like to try and sort this topic out for myself and for anyone else that may need it. Lots of people asking about D15B1 block and A6 head compatibility. I’m in need of a head for my 90 hatch STD with the B1 motor and have found what I believe to be an A6 head from a 90 Civic Si.
So far my searching has taught me that…
-the stock B1 head and A6 head are from the same casting. Apparently the only real difference is the cam profile (springs too maybe?) and that this head will bolt on perfectly
-that apparently to be able to time this combo properly you need to run a different cam gear (y7/8) on the A6 head?
-After some more research however I have found that the part number for the stock cam gear on both the stock B1 and the stock A6 head is exactly the same. The website (hondapartsnow.com and every other site) also state that the part number is compatible with every model of 1990 Civic (STD/DX/LX/EX/Si)
-if this is correct I see no reason why I would need a y7/8 cam gear.
-there is also lots of confusion as to what timing belt to use.
I would like to state one last thing, I’m open to any form of criticism and would appreciate any help I can get on this topic. This is not a race car by any means and I know what a dog the B1/DPFI combo is and I’m ok with that, I’m after gas mileage and dependability since I drive a ton of miles for work. I notice one of the main reasons this questions stays so open ended is because everyone starts chiming in with “why would you want to waste your money on that…” or “why don’t you just swap a blank into it…” and I’d just like to try and stay on topic.
Any information/help is appreciated. Thank you all very much. ​​​​​​​

This is the head I have available for purchase. I would go with a stock B1 head (pm9-5) but I have none available nearby.

Pm3-4 head code

Stock 1990 Hatch STD cam gear

Cam gear compatibility

 

You can use the a6 head on that block. Not sure if your pistons have 16 valve reliefs though? Wasn’t the STD an 8 valve head?

You are right in that the A6 and D15 heads are the same casting, it will bolt on, you can use the D15 T-belt as the D15 and the A6 are the same height.

 

I appreciate that info. The D15B1/STD is also a 16 valve.