Something In my #5 Cylinder?

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A fiend of mine sucked the air cleaner stud thru a B1 head at redline in second .
The stud had backed out during the run , dropped into the carb and the intake valve went
Yumyumyumyum......

If I had seen the carnage with my own eyes I would have called BS !
 
stixx said:
What is the average distance of a spark plug to the piston at TDC? For sure less than one of the valves when open. So no way in hell the rod bearing can devellop that much clearance as to let the piston hit the spark plug. A loose bearing can be heard when it's out by ... 0.01"? Sure the spark plug is farther away than that...

Otherwise... what oldmanmopar said: something broke off somewhere and went through cylinder #5.
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I'm sure something went through it.

But the idea you can hear .010 extra clearance isn't true. I've seen .040 not make noise. It sounded funny on the starter, but it ran and would close up the plug.

It also depends on the piston he has. Something is closing the gap WHEN THE RPM GOES UP.

That tells me it's gaining length somehow.
 
When you get into everything, let us know what you find! Curious to see what is going on there.
 
What pistons do you have in that engine, OP? I'm wondering on your actual CR and also how it could hit the plug. What exact plug are you using?
 
I'm a little curious about the connecting rods. Are they aluminum? are they new? did the builder check and record the deck height on every cylinder?
one thing I noticed from the bore scope pic is that whatever made all those dents in the piston crown is obviously (much)harder than aluminum. I think I would definitely pull the head, because there has to be corresponding damage to the combustion chamber.
 
I cast my vote in with the guy that recommended a complete teardown.
And agree with the guy who said something like; "you can pay me now or you can pay me later.
I haven't seen that kindof damage often, but every time I did, it was way worse than what the boroscope showed.
If I hadn't seen the no-other-damage, just a closed-gap plug...... it might be a different story. But that plug could be keeping a deadly secret.
 
Crazy things happen inside these engines and sometimes you get lucky sometimes you don’t. My sons engine broke a 5/16-1/4 inch piece of a stock Edelbrock valve off. (Number 3 cylinder) We did a leak down to find it. We pulled the head and I repaired the head. While he was gone I decided to work on it and don’t ask me why but I climbed under and turned the engine over by hand. The engine suddenly stopped so I turned it the opposite direction and it stopped again. I pulled that head and the valve piece was stuck in number 6 piston. The piece went through the intake to the other side. I dressed it up and reassembled it and ran it three more years of 10 second passes. On rebuild I found it smashed the ring land slightly but not enough to hurt it. We lucked out and I hope you do too.
 
Demonracer said:
IMHO, I'd pull the cylinder head & check the inside of the cylinder as well as the top of the piston. I would also roll the motor over by hand a few times just to see what might be happening. Just my .02.
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I`d pull both heads ! If u end up having to pull the engine it would be liter anyway !
 
Thanks for the reply guys. Bore scoped again last night and found a chunk of #5 piston is gone. See picture below. Well, regardless of what happened I'm pulling the engine this weekend. I did Drag Week this year with this new combo. I think I was running too much timing and got into some detonation. Backed the timing way off and now had the tune just right but I think the damage was already done.

Boost learning curve I guess. I'll inspect all pistons and bearings but maybe I'll get lucky and only need to replace #5 piston rings and bearings? We'll see. Hopefully the head isn't also hurt.
 

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Was that a forged piston?
 
Walker434 said:
Thanks for the reply guys. Bore scoped again last night and found a chunk of #5 piston is gone. See picture below. Well, regardless of what happened I'm pulling the engine this weekend. I did Drag Week this year with this new combo. I think I was running too much timing and got into some detonation. Backed the timing way off and now had the tune just right but I think the damage was already done.

Boost learning curve I guess. I'll inspect all pistons and bearings but maybe I'll get lucky and only need to replace #5 piston rings and bearings? We'll see. Hopefully the head isn't also hurt.
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Glad you found that, but to me, that doesn't explain the plug getting closed up.

It's hard to tell from a picture but from what I see that doesn't really look like a detonation issue. Usually detonation looks a lot more ragged. I suppose if you had enough time on it after the failure, the heat from combustion could have smoother it out some. And the piston is usually pretty thin there so if it was detonation, you may want to get your piston guy to drop the rings another .100 so the tune up isn't quite so sensitive.

I'd rather lower the rings and get the tune up window wider than keep the rings up so high a small tuning error will eat parts.
 
I believe you probably should drop everything and go get your lottery ticket right now. I'm guessing something being bent or otherwise deformed is the reason the plug keeps getting collision damage.
 
Ring gaps butted together and popped the piston top? Can’t seem to tell in the pic. I run my gaps at .032 on cast pistons. But you’re running 10 psi w/o an intercooler on gasoline - risky combo. What is your timing retard pulled to at 10 psi?
 
Garrett Ellison said:
I believe you probably should drop everything and go get your lottery ticket right now. I'm guessing something being bent or otherwise deformed is the reason the plug keeps getting collision damage.
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Yeah, I thought about that. Maybe a good sized piece of that piston got bashed into the piston by the plug.

But...why is it closing the gap only at RPM. That's what has me head scratching.

I've run my piston to head clearance and intake valve to piston clearance as close as .040 and turned it over 8k and neither hit anything unless you were gaining bearing clearance.

I've done .048 on aluminum rods and it cleaned the carbon off the piston but it never touched the head or the intake valve, and that was shifting at 8800.

The fact that it's RPM related is what is bothering me the most. The fact that the engine either failed a piston or swallowed something is relatively benign.
 
T56MaxTorq said:
Ring gaps butted together and popped the piston top? Can’t seem to tell in the pic. I run my gaps at .032 on cast pistons. But you’re running 10 psi w/o an intercooler on gasoline - risky combo. What is your timing retard pulled to at 10 psi?
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Wow. Hadn't considered that. But a real possibility.

You can't see enough of the bore though to see the damage that happens to the bore when the rings butt.

But that's a very real possibility.
 
I don't if it's bushed for floating rods, but if it is, I'm thinking bent wrist pin. At low rpm it's probably seized up enough to keep the bend situated downward, but at high rpm, the inertia gets high enough to spin the bushing in the rod bore, effectively lengthening the stroke. If it's pressed fit, it would probably involve the pin bore being cracked.
 
These are CP Carrillo forged Boost spec pistons. Was running 27* of timing during drag week. When I saw signs of detonation I dropped that back to 23*. It seems very happy at 23*. I think I was also running too hot of plugs? During drag week I ran NGK BKRE6-11 plugs which is a 6 heat range. I have since dropped back to a 7 heat range NGK... should I go colder when it all goes back together?
 
Walker434 said:
These are CP Carrillo forged Boost spec pistons. Was running 27* of timing during drag week. When I saw signs of detonation I dropped that back to 23*. It seems very happy at 23*. I think I was also running too hot of plugs? During drag week I ran NGK BKRE6-11 plugs which is a 6 heat range. I have since dropped back to a 7 heat range NGK... should I go colder when it all goes back together?
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How much boost? Even a 7 is pretty hot if you are going over 10 pounds.

IMO, when doing drag week or just driving around, you can use a pretty warm, extended tip plug. Just don't mash on it.

When you get to the track, don't use a projected nose plug. Even with the same heat number the tip gets too hot for boost.

I ordered a NO Good Kind plug catalog and the dilrods sent out a non automotive catalog. If I had the right book I'd look that plug up and see what it is exactly. I don't know my NGK numbers very well.
 
Ok, so I used the catalog to see what you have.

That plug is a 3/4 reach, 5/8 hex resistor plug with a factory .044 gap. Unless you have a big ignition that gap with boost may cost you some power.

Still can't get my head around NGK nomenclature.

I need to do more research.
 
Ok, that plug in a Champion is an RC12YC and that's way too hot for any boost. And that extended tip is not good for boost.

I think to get your tune up under control and happy you need to run that plug when street driving and run an 8 in an NGK under boost, and maybe a 9 if the plug says it isn't happy.

And never an extended tip while beating on it.

Just my humble .02 and it's worth way less than you paid for it!!!
 
Walker434 said:
These are CP Carrillo forged Boost spec pistons. Was running 27* of timing during drag week. When I saw signs of detonation I dropped that back to 23*. It seems very happy at 23*. I think I was also running too hot of plugs? During drag week I ran NGK BKRE6-11 plugs which is a 6 heat range. I have since dropped back to a 7 heat range NGK... should I go colder when it all goes back together?
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A piston manufacturer doesn’t matter as much or forged or hypers, if the ring gaps butted together. Butting them up on boost is a common issue around the forums.

I’m glad you run water/meth, what ratio?

In my opinion, your timing was way too high at 27. That’s less than 1 degree of timing per psi of map. If you experienced detonation, you may have damaged it then. Detonation is a wild animal under boost.
 
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