oufan2929

Some people call it the shoulder strap, wikipedia calls it the side electrode. Anyways, what are some options when the side electrode bends over and touches the center electrode. Basically closing the gap. It's got a tiny nick on the side of the electrode as if something hit it. Car was running funny, then put a new spark plug in and it's running like a champ again. Checked the compression and it's perfectly fine. It's done this twice. The first time I was hoping for a fluke, but it's done it again, so now I'm counting my blessings I didn't hurt anything. What are some possibilities from you FI experts. Oh, and it's got a paxton on it making about 15lbs. of boost. Thanks!--Andy

crashly

its called a piston.....

SilverSS

iTrader: (30)

simple as that. that piston wants out.

dschmittie1

iTrader: (64)

You might want to try indexing the plugs to help prevent that from happening.

98Z28CobraKiller

iTrader: (17)

Pull the motor and check it before it really lets go. I have had that happen to 2 motors and both times I wasted the block by not taking it apart. This is NEVER EVER a good thing.

oufan2929

can someone expand on this brilliant observation? what causes the piston to be able to reach the electrode?

Fireball

iTrader: (21)

if you're running a stock shortblock at 15 psi...it means you probably are quickly running out of borrowed time

oufan2929

Built bottom end...I'm wondering if the machine work was done improperly...

Fireball

iTrader: (21)

wonder what your effective deck height is.

but the fact that it doesn't happen all the time makes me think something is stretching which is a sign its about to go *poof*

Shawn @ VA Speed

iTrader: (3)

the heads would have to be milled excessively for a piston to hit the plug.I'm leaning more toward detonation-can you post up pictures of the plug

oufan2929

Unfortunately I regapped the plug. So I don't have a pic of what it looked like. Could it be a main bearing gone to crap?

'Trust'

iTrader: (24)

On the yellow car? Could be detonation, throw some 101 in there and see what it does for awhile.

98Z28CobraKiller

iTrader: (17)

I vote to take it apart or atleast get a bore scope in the hole soon.

Dean95z28

iTrader: (7)

I agree with this guy!!! You need to get a bore scope in there to at least see if it is the piston hitting the plug.

98Z28CobraKiller

iTrader: (17)

May have busted a ring land.

oufan2929

There's a few nicks on the top of the piston, about where it'd hit the spark plug. Compression is still good though. My latest thought is worn out rod bearing?

crashly

piston rocking in the bore : wrong piston clearance or wrong pistons
big end bearing wear or wrong clearances
cylinder head machined excessively , too much taken off
block machined excessively, wrongly set up in mill
wrong spark plug reach or type of plug, there is a 3/4 reach and shorter...plus projected plugs , and non projected...

it that a brilliant answer or what ???




Quote:
It's got a tiny nick on the side of the electrode as if something hit it.

oufan2929

Just what I was looking for crashly thanks.

Now, if the heads or block were milled excessively, would I not be hitting other spark plugs?

Could it be just as simple as buying a shorter spark plug? None of the other plugs the same length hit...

I was told by a very informative guy that he thingks its the rod bearing which makes sense. Allowing it to stretch a little at high rpms. Thoughts???

John at J&S

How could the piston hit the side of the electrode?

Do a leak down on that cylinder. Sounds like there was something flying around in there.

oufan2929

So would adding a washer to the spark plug be asking for a blown motor? My shop is wanting to do that to "see if it fixes it"...