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Discussion Starter #1 (Edited)
Hey everyone.

I went to the track today to take my '93 del Sol Si for a spin. It has (or had...) a built NA d16z6. During the last Dyno tuning I made 158whp. I love this little SOHC but today something happened....

I came around a corner at the track, tried to downshift and it felt like I missed the gate. I can't recall if I over-revved the engine (I'll have to watch the video) but I heard a noise. I pulled off the track and tried to start but all I got was a CLUNK.

I had it towed home. I pulled the plugs to try to move the engine at the crank. I noticed plug #1 had what looked like some markings on the base of the plug around the electrode. Then plug #2...

Trying to take #2 was much harder than it should have been. When I finally got it out I could see that the electrode end looked entirely smashed in. I pulled the valve cover off and everything there seems ok. Doesn't look like. Valve dropped (I can see all 16 shafts and the connections to the springs).

What could it have been!? Did I actually drop a valve? Valve float (I'm using the Rocket Motorsports valve springs and Ti retainers with the stage 4 re-grind camshaft)? Detonation?

The timing belt still looks good (I have the cover off to access the adjustable camshaft gear) and the camshaft gear is still sitting at 1* advanced.

I've attached pics.

Plug from cylinder 2:


Plug from cylinder 1 (much less damage but still evidence of something contacting the plug):
 

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Meat Popsicle
91 CRX Si
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2,936 Posts
Have a cylinder leakage or compression gauge?

Can you turn the engine over by hand?

Is the mechanical timing still correct when you rotate by hand?

I would imagine that even severe detonation would melt the electrode and cause a misfire before the entire tip of the plug melted.
 

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Discussion Starter #5 (Edited)
I think I may need to start preparing for the possibility that the motor has given up her ghost...

I have a d15b sitting in the garage that I bought three years ago when I spun a rod bearing on my stock d16z6. That spun bearing is what eventually lead to this current build.

I have to see what is salvageable from this motor and what I can transfer over. I think stock bore and pistons will suffice this time! A high-revving d15 sounds nice!
 

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Discussion Starter #7
You think the bearing went out and hit the plug?
I'm starting to think that it dropped a valve. Wouldn't be surprised if one of the valve heads broke off due to fatigue from the extreme stress. It might also explain why plug #1 was slightly damaged. If the port is open due to the valve breaking off, some of the debris may have gone into cylinder one.

I had ACL race bearings installed when the block was rebuilt. But at this stage anything is possible.
 

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97 honda coupe
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thats alot of aluminum, not just a little. i would be scared to keep running that motor if that much aluminum came off of my piston. could have easily been a clogged injector leaning out 1 or 2 cylinders and causing detonation.
 

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Certified O.G.
A Shitbox
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could have easily been a clogged injector leaning out 1 or 2 cylinders and causing detonation.
My first thought exactly.

I know it's a slim chance as I don't recall if you're using an RTP or some sort of logging, but if so..... were you datalogging while running at the track? Seems to easy I know but I figured I'd ask.
 

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Discussion Starter #11
First step is to see if you cracked a cylinder wall like I did.
We'll find out soon enough.

My first thought exactly.

I know it's a slim chance as I don't recall if you're using an RTP or some sort of logging, but if so..... were you datalogging while running at the track? Seems to easy I know but I figured I'd ask.
It would really be a shame if that were the case. I had intentions of installing RDX injectors before my last tune but fortunately/unfortunately that didn't happen because the hats were missing (eventually found them).

To answer your question, I m not data-logging.
 

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Discussion Starter #12
I downloaded the video of the incident onto my Mac. I'll get around to posting it for everyone's viewing entertainment.
 

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Classic Man
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Ive seen this. Chances are some valves wont have their heads attached to their stems anymore. :(

1-2-1, 2-3-2, 3-4-3, usually the causes.


The collateral damage is from massive amounts of metal flying around and oscillating in your intake system.

The last time I pulled a plug like that, the head looked like it was blasted 60-70 times with a shot gun, and the piston was see through.
 

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Discussion Starter #14
Ive seen this. Chances are some valves wont have their heads attached to their stems anymore. :(

1-2-1, 2-3-2, 3-4-3, usually the causes.


The collateral damage is from massive amounts of metal flying around and oscillating in your intake system.

The last time I pulled a plug like that, the head looked like it was blasted 60-70 times with a shot gun, and the piston was see through.
Lol!!!

Yesterday I started the painful process of disassembling the motor with the minimal amounts of spare time I have. I only got as far as removing the throttle body before something else more pressing took my attention away but what I found has me convinced it was an intake valve.

The back of the throttle body butterfly has fragments of metal splattered all over it. There is also some oil in it as well. I can imagine how flying shards of metal likely flew up into the intake manifold and toward the TB. I expect that piston two might look a little aerated. I'm more eager to see the extent of the destruction now once I pull the head off than seeing if it's salvageable.

When I have it all apart I'll create a new thread with pics as a warning to others!! Ok... maybe not a warning. Perhaps more of a "learn from my mistakes" kind of thread.
 
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