Spark plug crushed... how bad am I screwed
May 21, 2009, 03:55 AM
#1
Spark plug crushed... how bad am I screwed
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.
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.
Last edited by recompile; May 21, 2009 at 03:58 AM.
May 21, 2009, 07:41 AM
#2
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.
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.
May 21, 2009, 08:27 AM
#6
Evolved Member
iTrader: (6)
Join Date: Mar 2009
Location: Reading, PA
Posts: 503
Likes: 0
Received 0 Likes
on
0 Posts
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.
May 21, 2009, 08:58 AM
#7
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?
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?
Trending Topics
May 21, 2009, 09:24 AM
#8
Evolving Member
iTrader: (1)
Join Date: Jan 2007
Location: cali
Posts: 247
Likes: 0
Received 0 Likes
on
0 Posts
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?
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?
May 21, 2009, 10:27 AM
#10
Former Sponsor
iTrader: (44)
Join Date: Jun 2004
Location: Charleston SC
Posts: 1,159
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
May 21, 2009, 10:35 AM
#11
Evolved Member
iTrader: (1)
Join Date: Nov 2004
Location: Corona, CA
Posts: 583
Likes: 0
Received 0 Likes
on
0 Posts
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?
Last edited by turbolarry; May 21, 2009 at 10:41 AM.
May 21, 2009, 11:45 AM
#13
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?
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.
May 21, 2009, 12:00 PM
#14
Evolved Member
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...
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...
