I went to the drag strip last night, my first run the car felt odd in 4th gear. As soon as I let off I could hear a strange rumble to the engine, basically a Subaru mod. I knew one of the cylinders wasn't firing, I was sure I had floated & bent a valve and the engine was junk. Pulling into the pits, I was able to identify the cylinder by pulling plug wires until there was no change in idle.

Not 100% sure what happened to my car, all I know is something smacked one of my plugs. The ground strap was smashed into the tip and the insulation cracked in half.

I towed it home to be safe, and did a quick compression test... came back fine

:: big sigh of relief ::

I had some random plug (not IX plug), put it in and the car idles fine. I'm gonna put a new set of plugs into this afternoon and see if it idles & drives OK... hopefully no major damage but who knows.

Looking back at my log, I only revved to 7700, but I have doubts about FP 4R on stock valvetrain even though they claim it's safe to 8K. There was a bit of knock but nothing major... 1's, 2's and 3's

Any thoughts would be helpful.

 

UPDATE: I borrowed a borascope and looked in the cylinder. I can’t see anything wrong in there.
I used a brand new compression gauge and got 130 lbs on all of the other cyls and 120 on the one that had the bent spark plug. I put some oil in that cyl and did it again and got 120 again.

Maybe some minor valve damage? I suppose a leakdown test is in order.

 

seems like this type of issue is becoming more evident in the community.


Ibe intersted in learning wat actually caused it


did you check you check the blades on the back side

 

Subscribed!! I have seen this come up a few times in community and I am also very interested in finding out what is really causing this.

 

i know someone this had happend to, his engine sounded like a subi.

he chipped a piston, the car would start fine though.


GL man hope you sort everything out,,,, dont take this the wrong way but good excuse to build the engine

 

Id hate to do it, but Id pull the head and see if that chunk is in there. I would hope its just a chipped valve or maybe just lodged in somewhere where i t cant fully close or something. Prob gonna bet with a chip though.

 

In it for details......if the piston hit it WHY?

If the comp test was WNL i suppose a part of a valve could have broken off but it seems like a good amount of compression of the ground strap enough to crack the insulator from what i can see.........interesting......

Just throwing this out but i'm sure you had the correct plugs in there right?

 

You sure there are no marks on the piston, in that cylinder? I don't see how a valve could have hit it as the valves should always open fully without interfearing with the plug and the only other thing in there is the piston.

Maybe drop your oil pan and check to see if a rod stud has stretched allowing the piston to slide higher in the cylinder hitting the plug.

BTW is this on cylinder #1?

 

It's cylinder #3

I had one step colder Denso IKH24's in there. I put them in about a month ago, shortly after installing the cams. Before that, the car only had ever used the factory NGK ILFR7H's.

 

something was in your cylinder that caused the clearance between the piston and tip of the plug to close. could be a piece of the stock piston, could be a piece of the head casting that chipped off.. i've seen tons of them fail at your posted HP.

i would suggest pulling the pan and the head. check the bearing and that piston for damage..

on the flip side this had happened to me before and i threw a new plug in finished up One Lap of America and came home... 6 months later i pulled the motor to find a stock piston missing a pretty big chunk.

 

Sorry man, but a crushed plug like that is knock. I like the optimisim though.
"Really bad detonation can physically crack spark plug insulators..."
http://www.machv.com/broksparplug.html
or there's this one;
"Extreme detonation can also cause plug meltdown."
http://www.machv.com/melsparplug.html
Don't take that the wrong way and I'm not trying to be mean. It sounds like the motor is checking out and hopefully your luck holds out.
How much boost were you running?
What octane did you have in the tank?

 

My plug looked the same when I pulled them. This is what I found when the head came off.

 

This was a quarter mile run, and I only hit about 28psi. 93 octane + meth.

It's hard to see in the pic, but there is physical smash mark on the ground strap (see how there's a shiny part with no carbon?) so something definitely hit the plug, it was not crushed because of knock.

 

wow, this happened on my dsm last year...

out of whack-tune + detonation = intake valve gets cracked and a piece drop into cyl #3 = dsm sounds like a subaru = not so fun times.... lol

and youre compression test #'s were only 130????

good luck man...

 

ouch