D15B7 Top end in 89 CRX?

We may earn a small commission from affiliate links and paid advertisements. Terms


New Member
Hello to all… I bought my CRX DX in February of last year, it had the D15B2 motor with DPFI :eek:. I still love this car…. The gas mileage is great and it’s all-round a blast to drive, (now that I’ve rebuilt the entire drive train / suspension in the front end.)

Since I got the car I’ve read five different articles on swapping from DPFI to MPFI. I’m going to take the plunge and do it. Most of the articles focus on using parts from the CRX Si motor, D16A6, swapping in the D16A6 cam shaft as well, wrapping everything up with a PM6 ECU.

I’m fine with all of that, and I understand how to do the swap. My question is; Can’t one simply use the entire top end from a D15B7 instead of the Si? Before you answer…
The catch being that you must also commit to a OBD1 upgrade (P06 ECU)? Am I correct in understanding this to be the case????
My reason for considering going this route is that Si models are hard to come by in the local Pick-a-Part yards near me.

So, the only other thing I must make a decision on… The Head that is currently in my 1989 CRX DX is stamped PM#-13, 91… I believe that the head has been changed, doesn’t the 91 denote the year of manufacture?
Should I swap the whole head from the D15B7 over to my D15B2, or just swap over the cam? It’s my understanding that the head castings are identical. I’m just looking for suggestions on this one.

Thanks for all of the help… HondaSwap.Com has proven invaluable to me in doing my research on my CRX and it’s motor!!! Keep up the good work, also I plan on posting pics of my teardown / build. I hope that this will help others!
Yea that would work fine. but if you're going to go through the effort of converting to obd1 and swapping heads anyway, why not just swap a z6 head on there?
I'm pretty sure I could go that route... P28 ECU instead right? But everything else stays the same aside from the Vtec head (z6)? How well do you think a D15B2 block with 175K miles on it will hold up to all of this?

I know that it's been taken care of I have all of the original service paperwork. Oh and is there any way to verify the age of a Honda block, maybe by casting #'s, like on the heads???

I'm not certain that this car has the original motor in it given that the head seems to have a newer date stamp than the car. But i guess i'll get an idea of it's condition once I take the head off.
I have a y8 head with fairly new valves and intake. it needs vtec solenoid. let it go for cheap.
I would be interested!!! One question though. Wouldn't I need a different cam gear to run a y8 head -if it still has the y8 cam- on a D15B2 block?
When you do any sort of mini-me, no matter what head/block combo you go with it is recommened that you use an adjustable cam gear to zero out the cam timing, if not it will be 1/2 a degree off.
Guess I better start saving for the Skunk2 cam gear I was looking at!!!
i used stock gear on a b7/z6 and was fine. and I highly recommen ARP head studs and timing belt from the head you decide to use.
I was planning on the ARP Studs, even if I didn't go Vtec. But that bit about the timing belt is very useful to know. Thanks for the info / help!!!!

My original reason for not going with Si / Vtec parts... well there are two actually. Si hondas are hard to com by where I am in So-Cal @ the pick-a-part yards, often times the yard pulls the motor/trans before the car makes it to the lot. And second, smog checks are a SERIOUS pain in the ass in California!!!!

I'm going tomorrow to find out if my car is a "Test Station Only" vehicle.... That will be a big factor in what I decide to do. Thanks again for the info, it is all appreciated!!!!!
Can’t one simply use the entire top end from a D15B7 instead of the Si? Before you answer…
The catch being that you must also commit to a OBD1 upgrade (P06 ECU)? Am I correct in understanding this to be the case????
that is not correct - the OBD0 distributor for the 88-91 CRX/Civic Si/HF will bolt right onto the D15B7 head, so using the D15B7 head, intake manifold, etc. is no different than using the D16A6 head, intake manifold, etc. - however, there would be one difference: since the D15B7 has OBD1 injectors, you would not need the injector resistor box when making the DPFI to MPFI wiring changes
so you would strip the ends of all the wires going to the resisto box,and solder them all together
Oh how quickly plans can change!!!! I was out at the local pick-a-part today and came across a 1991 CRX that had a JDM ZC SOHC swap! Bingo! Pulled the Throttle body / Intake manifold, snagged the whole engine bay harness, and grabbed the dizzy, along with the PM6 ECU....

So, tomorrow I'm gonna go back and pull the head as well. I grabbed what I could, seeing as how these are the required parts to do the MPFI swap. Would have gotten the head but by the time I found the car I only had 30 minutes untill the yard closed. Didn't want to chance missing out on the parts I could get in the time I had. I'll post pics tomorrow or Saturday.
c-rex-beat; yes, it's a non Vtec head. Since emissions / smog checks are a real bitch here in So-Cal, I decided to stick with the A6 head. Draws less attention if some Highway Patrol Officer decides to pop the hood...:ph34r:

Checked out the Intake and Throttle body this morning; turns out the TB is stamped "JG Racing"
Looked them up and found this...
JGE Home
Turns out that if you send them your throttle body, from a ZC in this case, along with $135, they bore it out to the maximum diameter (59mm) and rework the internals too. So I'm super stoked now. Especially since the yard only charged me $50 for it... including the TPS.

So I made it back to the Pick-a-part today. Super excited... Pulled the head, got the complete head, along with the valve cover, cam gear, and timing belt cover. I also had enough time to get under the car and I managed to pull the entire rear trailing arm / disk brake assemblies, along with the factory rear sway bar!!!.... But that will be a discussion for another day, and another forum ( but I still might sneak a few pics of them, just cause I'm proud that I landed them :) )

I work in the morning Saturday, but I'll try and get pics taken and up once I get home tomorrow.

Thanks again for all of the input and ideas / suggestions. This is still a learning curve for me, but I'm having fun with it!
Made it home from work and got some pics taken, so here goes...

My 1989 DX Beater...



Engine bay is pretty much stock...

So here are the parts I picked up on my days off this week. Can anyone help me ID this head??? I have looked at several head Identification lists on several forums but I have yet to see this actual designation "PM3-6"






Looks yummy!!! not.... Hopefully I can get the head out to the local shop sometime next week. While they have it apart, I'll get them to give me the #'s on the cam so I can ID it. More pics in the next post....:D
i think its just a basic non-vtec zc. i cant recall if the actual a6 head said pm3-6 or if it said pm-6..

What are you going to have the shop do to it?
my A6 (off a 91 Si) is printed PM9-5... my Y8 (got off ebay... believe its off a 98 automatic Ex) is stamped P2J-4