D15B8 block, PM8-1 head (8-valve)

I have a 91 CRX that used to have a D15B7 block and PM9-1 16-valve head, DPFI. The head burnt a valve and the rings are shot.
Now I have a D15B8 block, PM8-1 head (8-valve) with DPFI, same distributor and main pulley as the b7. All the timing marks line up perfectly for TDC. When it's running the timing is at the red middle mark which is where it's supposed to be for the 16v head. but it idles at ~1200 even with the bypass plug jumped. The IACV was still plugged in which might make a difference, but I think my Chilton manual says the D15B8 is supposed to be at 12 degrees timing? I've searched and can't come up with anything about 8 valve timing

 

the PM-8 head is from the 88-91 CRX HF - ignition timing for the HF is 14 degrees BTDC (+ or - 2 degrees) at 600 rpm

 

Thank you, that helps a lot. I went to check the timing again tonight and it was at the middle red mark on the crank pulley I have (B2 or B7). I'm ordering an adjustable timing light to be able to set it from the tdc mark instead of guessing at the distance. But when I was checking timing, after a minute or so the rpm's dropped from 1000ish to 850ish and the timing light was showing TDC. The timing wire was jumped and EACV was unplugged, all accessories and lights off. If I gave it just a little gas the timing shot back up to within the marks. I let the car sit again and timing was at 17 (assuming the pulley I have is marked at 18)
Does anyone know why the timing light would all a sudden jump to TDC? the motor definitely sounded a little different so I'm assuming the light was working properly

 

Also, should I adjust the idle before setting timing? Even with the 16v head it idled at 850-1000. I cleaned the EACV and it was still higher than spec. Would the ECU have anything to do with it?

 

Well, I just took it for a test drive, it smoked whiteish but that might be burning off whatever is gunked up in the cat. It's running a little hot but will cool down if I take it easy. it also seems like its lacking power. Does that sound like a timing issue? The idle is also bouncing between 1000-1200 even after cleaning the eacv, i'm going to clean that again and see if it helps. at this point i'm stumped as to why it's running so bad

 

Bad timing can make it run hot. Is this a recent issue? Did this start happening after you've done something in particular?

 

I think the issue has something to do with the motor swap and running an 8 valve HF head on a 16 valve DX car? But I'm leaning towards the timing being too advanced and making it run hot. The next thing i'm going to try is running it without the cat to see if it still smokes or if the cat is just dirty from the old motor burning a lot of oil. Compression is at 120 across all 4 so the rings could me starting to go but craigslist be like "motor runs good"

 

I doubt the head is the issue. The HFs are MPFI though, i'd be more inclined to think that there's a wiring fault when converting mpfi - dpfi.

If you can get the ignition timing to line up to within a few degrees of the marks, that's not enough to cause the motor to run perceptibly different. If you're struggling to get the marks to line up though, double check the mechanical timing.

I'd be working on those codes first though.

 

I don't think it ever was a MPFI car though, when I bought it it had the dpfi intake manifold and still does now. I just double checked the mechanical timing and it's still lined up. I checked the ecu and it says PM5 on it. It threw a cel on the test drive a couple minutes in like it always did even when it was running fine (Idk why I never tried checking before to see what it was) but when I turn the key the red light goes on then off but doesn't blink any codes. Am I not checking for codes the right way? They should be stored in the memory


www.hondata.com/techecuid.html
^ecu identification
The last 3 are A30 so it might be the original ecu for the car. But will swapping from a 16 valve to 8 valve head make a difference? It's still the same cam pulley and distributor and the blocks have the same dimensions and specs. So unless the pistons and head are that much different it should work unless I'm missing something which I might be