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Discussion Starter #1 (Edited)
Hello everyone.

On May 22nd I took my car to the track. It's a '93 del Sol Si with an NA built high compression d16z6. During the last dyno tuning session it was making 158whp.

All was well until CLUNK... and then it wasn't. I had it towed home. All signs were pointing toward a dropped valve.

I finally was able to pull the head off and my worst fears have been realized... Painful destruction.

One of the exhaust valves in cylinder 2 dropped. The head is destroyed. The piston is destroyed. There are gouges in the cylinder wall of #2.

I'll likely use the d15b 3-stage VTEC that I've had sitting in my garage for the last 2 years and transfer what i can over. The camshaft, valve springs and Ti retainers are still good. I have a spare z6 head for it all to go into, it's just not ported and polished like the last one was.

Take a look at the pics. I took a shot of each of the pistons. It looks like some of them actually had some contact with the valves. I wonder if the 1* advance we did during the tuning session caused it. With P29's and a relatively aggressive camshaft and VERY narrow tolerances, I wonder if that led to the failure....

Head:

Pistons:


Piston #2:


Piston #1 (note the fragments):


Piston #3:


Piston #4:
 

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Discussion Starter #3
PG6s are a better choice than P29s for an OEM highcomp piston for your next build
In retrospect, yes. The PG6's would have been the better option.

If I use the d15b like I suggested in my post, I would consider the PMS-A00 (01-03 GX) with a y8/z6 head gasket. It allows for 10.81:1 compression and 0.030" piston to deck height.
 

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Holy piston destruction batman.

Edit: That valve didn't eat his wheaties that morning. Pussy. Just gives up like that.
 

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Stock or after market valves? drop at the retainer/keeper or the neck break?

Did you clay your engine prior to assembly?
 

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Discussion Starter #8 (Edited)
Exhaust valve, not intake.
You're right. It is the exhaust valve. It was late and hard to see through the tears. Correction made. Thank you!

That sucks big donkey penis
Yes. Yes it does.

Stock or after market valves? drop at the retainer/keeper or the neck break?

Did you clay your engine prior to assembly?
Stock valves. I had them serviced when the head was built. Lesson learned for next time.

It broke at the neck.

The engine was built in stages over two years. The bottom end was built two years ago. It was bored out to 75.5mm, crank was serviced, decked, P29 pistons, installed in 2015. I was using a stock head with a stage 2 Bisi camshaft at that time. In 2016 I had a spare z6 ported and polished and resurfaced. Rocket Motorsports stage 4 camshaft, valve springs and Ti retainers installed. They head was installed by my mechanic (helped to essentially build every aspect of the car). I honestly don't know if it was clayed but given his experience with building engines I would have no doubt that it was. If there were any concerns I would have been informed.
 

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They head was installed by my mechanic (helped to essentially build every aspect of the car). I honestly don't know if it was clayed but given his experience with building engines I would have no doubt that it was. If there were any concerns I would have been informed.
I would ask for sure . . . hitting every single valve relief points to it wasn't unless you did move the cam so far from where it was setup that they never checked where you ended up at.

How much was the head milled? I've noticed that on a lot of heads that were decked a bunch . . . the radial valve clearance goes away since the valve is moving physically closer to the piston yet the axial clearance still shows up fine.
 

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Once a valve head gets loose from the valve stem, the valve piston timing is all over the place and the probability that other valves would touch piston tops is very likely. That first stroke when the piston tries to smash the valve head into the combustion chamber stretches the shit out of the belt, if not making it skip teeth - so, the aftermath shows things that are artifacts of other damage.
 

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Discussion Starter #14
Hey thanks everyone for your condolences. She was a good little engine...

I think I'll be using the d15b that I have sitting in the garage and simply throw some of what I can from my z6 onto it. I don't expect to make the same kind of power I was with my z6 but my hope is that if I f*** with it less than I did the z6 it may be more reliable and still make decent enough power.

I'm not taking the car to the drag strip. I run it on a track. What's happening in the driver's seat is more important than how much power the motor is making.
 

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Discussion Starter #16
sad news, 158whp is sick for an NA d build.

Much good luck to yr upcoming d15b franko engine!
Thanks Crooked Muffla.

I was pretty f***ing ecstatic with it. Short lived but it was a blast.

Right now just looking to get a running motor in there. I NEED to hit the track soon. The d15b with the y8 head with the bolt-ons will do for now. I'll be looking to swap that Rocket Motorsports camshaft, springs and Ti retainers in there eventually - possibly even get the spare Z6 head ported and polished. Also have those RDX injectors. I hope to be somewhere in the neighbourhood of 140-150whp after that.
 

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Thanks Crooked Muffla.

I was pretty f***ing ecstatic with it. Short lived but it was a blast.

Right now just looking to get a running motor in there. I NEED to hit the track soon. The d15b with the y8 head with the bolt-ons will do for now. I'll be looking to swap that Rocket Motorsports camshaft, springs and Ti retainers in there eventually - possibly even get the spare Z6 head ported and polished. Also have those RDX injectors. I hope to be somewhere in the neighbourhood of 140-150whp after that.
I'd be curious to see a dyno of the d15 build too

The numbers and power curves on NA d builds are always curious.

:3dbiggrin:
 

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Discussion Starter #19 (Edited)
I'd be curious to see a dyno of the d15 build too

The numbers and power curves on NA d builds are always curious.

:3dbiggrin:
I think the chances for some decent power are pretty good. A friend of mine and DSO member has a d16y8 (stock head, stock bore, stock compression) with an Edlebrock IM, header, 2.5" exhaust, 255lph fuel pump and RDX injectors. He had his motor tuned by the same tuner and on the same Mustang Dyno as me (last year when I made 156whp - literally the very next day) and he made 150whp. Legitimate 150whp. He made a post about it last year.

I haven't seen the dyno graph so I can't necessarily compare the curves of his to mine, but for simple overall peak power, that's only an 8whp difference in spite of the 0.5mm larger bore and P29 pistons I was using.
 

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total goofball
1994 Civic coupe EX
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I think the chances for some decent power are pretty good. A friend of mine and DSO member has a d16y8 (stock head, stock bore, stock compression) with an Edlebrock IM, header, 2.5" exhaust, 255lph fuel pump and RDX injectors. He had his motor tuned by the same tuner and on the same Mustang Dyno as me (last year when I made 156whp - literally the very next day) and he made 150whp. Legitimate 150whp. He made a post about it last year.

I haven't seen the dyno graph so I can't necessarily compare the curves of his to mine, but for simple overall peak power, that's only an 8whp difference in spite of the 0.5mm larger bore and P29 pistons I was using.
wow, impressive
 
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