Jeep Strokers

I have a 4.7 in my 90 wrangler running '95 wire harness and injection (obd1). Build specs are 60 over block,kb944 pistons, stock rods, stock head, comp cam, hesco adj fpr, bigger injectors, stock ignition.
I don't remember the cam model or injectors. The cam is mild as I am in California and need to pass emissions.
I originally had this motor in my xj till a tree jumped out and totaled it. At about 5k miles I broke #5 piston and at that time it was assumed to be a vacuum leak. I changed the intake and verified I had no leaks after reinstalling everything. Since then I have installed the stroker into my yj and have broken #5 piston again.
The piston is broken at the top compression ring and appears to be a pre-ignition problem. I have installed a new piston and have everything back together and now have a bad rattle that sounds like detonation. Using a stethoscope the sound is strongest at #5 listening at the cylinder head.
Base timing is at 12 deg and total timing is at 34 deg, my wide band o2 is reading 12.4-13.8 afr and engine temp is at 210.
if anyone has any advice on what to check please let me know I am at the point of pulling the motor in favor of a v8.
Thank you in advance, any thoughts are welcomed

1990 yj 108" wb 4.7 aw4 231/d300 dana 60 kp 14 bolt on 40's

I forgot to mention that the pinging noise comes on about 1800 rpm and goes away at 2600 rpms. It's quiet at idle and higher rpms. With a stethoscope I can hear the noise at idle but not without it.

Update: I changed to ngk 7373 spark plugs and it helped a little bit. The range of rmps that I get the ping is smaller. Also I have isolated that it is coming from cylinder 5 only, when I pulled #5 wire the sound goes away completely.
Has anyone ran into the obd1 pcm advancing the timing on 1 cylinder only? Or is there any other ideas that could cause this?

It's not possible for it to advance the timing on one cylinder only. You have something else going on like a good spot in that cylinder or maybe a lean condition? I'd swap injectors just to try something, but you might have to peak inside. Got a boroscope? Cheap ones can be had that work with Android phones.

dirt5track wrote:Using a stethoscope the sound is strongest at #5 listening at the cylinder head.

How are you doing this?

SilverXJ wrote:

dirt5track wrote:Using a stethoscope the sound is strongest at #5 listening at the cylinder head.

How are you doing this?

I have a stethoscope with a metal rod in the tube. I just touch the rod in the area I want to listen too, then move it around to other areas.
I have determined that I have an internal mechanical problem causing my noise. It may be skirt slap so I have decided to pull the motor and go through with my v8 swap. I appreciate the help guys. If anyone is in central Ca. I will have a 4.7 for sale that will need one cylinder sleeved or a new block.

Denotation won't happen at idle or under no load.