Piston hitting sparkplug

[jackhammer]

This is a NA shortblock with TT conversion. Its been running fine for a couple years, and all the sudden, this starts. Any ideas or theories? It doesnt make any knocking noises, the only noise is in the top where the piston and sparkplug meet.

My only theory is that this might be a longevity issue of the NA shorkblocks wearing out the piston pins because they dont have the oil squirters.

It could be a worn rod bearing, but the oil pressure has always been superb, all the clearances plastigaged out good, and a new pump was installed at the time of the TT conversion.

Discuss?

[Darkhelmet]

if the piston hit the plug you would have a broken piston, a broken plug, a broken rod and a fucked up crank.

[CHAN]

The piston would hit the valves before the plug.

Checked Compression?

I know i have seen some spun bearings and the oil pressure still be decent. With loose piston pins, From what i have learned it is not a noticable knock when they wear out either.

[jackhammer]

[quote=""Darkhelmet""]if the piston hit the plug you would have a broken piston, a broken plug, a broken rod and a fucked up crank.[/quote]As much as i would like to agree with you, i have a spark plug that has had its gap eliminated, and a piston that has a shiny mark directly in the center, and a car that otherwise runs fine

[quote=""92ttawdstealth""]The piston would hit the valves before the plug.[/quote]Seems like it, doesnt it?

[quote=""92ttawdstealth""]Checked Compression?[/quote]The owner of the car got 0 on that cylinder, but i dont know if he even knows how to check it

[Monochrome]

[quote=""jackhammer""]Seems like it, doesnt it?[/quote]

So what you're saying is, the motor is torn down and there are no signs of damage to the valves? Rockers didn't even pop off?

[bluej]

in for mysterious engine failure.

here's a really stupid question, is it the right part number for the spark plug? did something fail that made it longer?

could it be FOD? suck something in and somehow manage to squish exactly between the piston and plug?


just throwing out the crazier ideas to get you thinkin...

[jackhammer]

The motor is NOT torn down.

I stuck my trusty borescope in the hole and had a look around. I didnt attach the mirror to look at the valves, because we were short on time. Ill be taking a better look this weekend

[Monochrome]

[quote=""jackhammer""]The motor is NOT torn down.

I stuck my trusty borescope in the hole and had a look around. I didnt attach the mirror to look at the valves, because we were short on time. Ill be taking a better look this weekend[/quote]

Ah okay...

[Hannibalzero]

[quote=""jackhammer""]The motor is NOT torn down.

I stuck my trusty borescope in the hole and had a look around. I didnt attach the mirror to look at the valves, because we were short on time. Ill be taking a better look this weekend[/quote]

Well, he said there was 0 compression on that cylinder, no? Did you confirm that?

[jackhammer]

This weekend

[J-Groove]

In to find out. Because umm WTF? That just doesn't make sense to me.

-john

[jrod]

ya i have not clue, would like to know why though. In for results.

[Gray Haze]

Rod stretch? Piston Swell? Excessive EGT's?

Ive seen this happen on a lot of hondas.

[Wolf_Zero]

I'm a little confused as to how this is happening. I would definitely think the valves would be hit before the plug unless either the plug is longer than normal or was somehow put down in there further than normal.

[TajMan]

You got wrong spark plugs that are too long.

Its possible for a chunk of something to enter the cylinder and be pinched between the piston/spark plug closing the gap, but you'd know the difference if that happened.

No idea dude.

[Hannibalzero]

Any luck figuring this one out Jack?

[DCIV]

[quote=""Darkhelmet""]if the piston hit the plug you would have a broken piston, a broken plug, a broken rod and a fucked up crank.[/quote]

sorry jack but dark is right, thats the only way its goign to happen.


Coop