This past weekend Im boosting through 3rd and some of 4th gear. Pulls strong, no unusual noises. I let off because Im quickly doing triple digits speeds. I coast for about 10 seconds down to a normal speed and when I get back on the throttle it sounds like its running on 3 cylinders.

I gently drove the quarter mile back home and pulled the plugs. Spark plugs 1-3 are fine but this was #4.



<U>Relevant Facts</U>
1.) Built GSR motor, assembled by me. Has 3,000 boosted miles on it.
2.) CP 9:1 Dished pistons.
3.) 89mm LS crank, Pauter LS rods.
4.) Benson sleeved. Block Deck was milled too much as adjustable cam gears are required to line up cams and crank to both be TDC. Cams set to -1*. Its unknown how much was taken off but its evident more than expected was milled.
5.) Stock GSR head, never milled or altered in any way.
6.) OEM head gasket bored to match 84mm.
7.) BKR7E spark plugs used. Gapped to 32
8.) Tuned by me, AEM EMS. Safe AFRs and safe timing values. No signs of detonation.
9.) Compression tests are OK so no serious damage done thankfully. All cylinders ~190psi
10.) Turbo is using a screen mesh instead of a filter but it's intact and undamaged.
11.) Compressor wheel appears undamaged as well, no signs of foreign matter.
12.) Was not over reved.
13.) If anyone replies to this thread and asks for information already provided, I will kick your ***!

Help me analyze what caused this. This has never happened before so I doubt it is a result of the engine however I do not see any signs of foreign matter. I see silver blotches on the grounding strap and electrode that may be melted aluminum. This has me very concerned! The only thing that is different this time is I torqued the plugs to spec which is tighter than I normally do it by hand. But it shouldn't be this close to the piston anyways!

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Update2 on page 5


Modified by Muckman at 12:18 AM 8/4/2005

 

hrmm, could this be a freak accident of a piston hitting the spark plug? if it did, wouldnt it bend 2 of ur valves in cylinder 4? since ur compression numbers are fine, i wonder what it could of had been.

 

The spark plug sits in the middle of the 4 valves so it would not come in contact with them. Since the electrode was not destroyed Im assuming the ground strap was just kissed lightly by whatever. Thankfully there is no major engine damage, yet.

 

Maybe the spark plug got so hot that the electrode became soft, then the boost pushed it upwards? .....hahaha...that's the dumbest thing i've ever said, but the only thing I can think of.

 

have you looked down the plug hole with tha piston at tdc ??? i would use like a flash light and see if there is ant marks on it , a 9.1 piston is dished so it would hit the head b4 hitting the spark plug, i know from a past engine that was decked way to far

 

Wow, man I cant really think of anything.
maybe you could get your hands on something that would allow you to look into the cylinder, to see if it did contact the piston.
Maybe it ran lean on cylinder #4 and the groudstrap got very hot and shrunk and when you let off the gas it allowed it to cool?

Eh both my ideas are iffy at best, if you need another opinion gimme a pm and ill swing through and see if i can provide some help.

 

I looked down into the cylinder and it looks ok actually. Some people suggested the blotches were detonation but none of the other injectors show any signs. Ive been using this calibration for 3 weeks now and never logged any knock.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">I looked down into the cylinder and it looks ok actually. Some people suggested the blotches were detonation but none of the other injectors show any signs. Ive been using this calibration for 3 weeks now and never logged any knock.</TD></TR></TABLE>


Check the rod bearing in that hole

 

but the psiton is dished and it is a gsr head so it would hit the head first and never hit the plug ,

 

Agreed. Perhaps something foreign entered the cylinder. Any chance a spark plug could arc itself together?

 

I take it that this happened earlier today?
Today was uber hot out some stations were saying it reached 100 degrees in the city. Maybe it did detonate. Running a custom intake manifold? maybe some weld broke loose inside?

 

hope it turns out good muckman

 

maybe a welding booger broke off from your ic pipes?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2point2 &raquo;</TD></TR><TR><TD CLASS="quote">maybe a welding booger from your ic pipes?</TD></TR></TABLE>

Possibility.

 

i think i would just put a new set in and check your a/f ratio and timing , and just go from there , cus your piston did not hit the spark plug , and for anything to get sucked into the turbo it would be smoked and you said it was fine , so i would just try again and see what happens

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C1CYA &raquo;</TD></TR><TR><TD CLASS="quote">i think i would just put a new set in and check your a/f ratio and timing , and just go from there , cus your piston did not hit the spark plug , and for anything to get sucked into the turbo it would be smoked and you said it was fine , so i would just try again and see what happens </TD></TR></TABLE>

Aggreed. Just take it easy and keep checking the plugs, just slowly work your way up into boost. and keep checking.
Goodluck Muckman

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B6tPoweredMx3 &raquo;</TD></TR><TR><TD CLASS="quote">I take it that this happened earlier today?</TD></TR></TABLE>

Actually it happened this past Saturday. It was cool that day about 70*-75. I just havent gotten time to look at it since then bc Ive been moving into my new house.

Thanks for all the responses guys. Im going to write it off as a freak occurance, put a new set in and drive it. If it breaks its gonna be on your conscience!

 

It's the heat that caused the electrode to bent upwards. It happened quite often for my other turbocharged car (a Toyota), but I kept replacing the same plugs over and over again and it would keep doing the same thing after a couple of hard highway pulls. That could also be an indication that the plugs might be a tad too hot for your power levels. Sometimes the car's tune can run great for a period of time, but it takes some carbon build ups, some unusual heatsoak, etc... to create a ltitle more heat in the chambers and bend the electrode.

When I swapped to colder plugs, it solved the problem.

 

Wow now theres a very insightful answer. Thank you!

Im already running 7 heat range. However my intake temps are on the high side (~130* on a hot 90* day) so that could explain things. I ran my NA plugs (gapped at 44 lol) for a week with a 6 heat range and it ran great but the strap showed definate signs of over heating. Ill try 8 heat range plugs.

 

higher numbers = colder plugs,

if you have a 7 then you want to goto an 8

 

Yeah I just realized my mistake and edited my post. I freaked out and thought I was running stock heat range plugs for a second.

What do you think about Tonys theory?

 

Tony's right, it's the heat, usually detonation will cause a huge temp spike.
Sometimes a cooler plug helps, sometimes not.
I've seen this in an SRT4 in cylinder 1 and in a blown mustang that had 4
of the ground straps actually droop down past the center electrode.

 

wow some very insightful info in this thread.

dont gsr's run 6 heat range stock as b16's do? if so then the 7 is only 1 step colder...

muckman do you have an egt gauge to check things out, especially since you said your iat's were in the 130 range. either way good luck with everything

 

I have seen this before aswell, it is the heat. change them out and your good to go.

Also, that is a great pic of that plug. What camera?

 

Good info Guys