KenGPW

OK to try to make a long story short.... I was driving along and a Z28 wanted to play. I dropped gear and when approaching 8k rpm the car just stopped accelerating and there was a sudden power loss. I knew what ever it was, was not good. I limped the car home on basically 2 cylinders. Car was backfiring and of course putting. Motor was knocking and tapping. Crazy thing is that once I hit 3000 rpm the car ran fine so I kept speed low and made it home.

When I got the car home First thing I did was pull the plugs. The tips of the spark plugs in cylinders 1&2 (front of car) were broken off and the white part around the electrode was missing. The plug in cylinder #3 was loose and backed out 3 1/2 full turns. The coil was also covered with carbon because of the leak. Cylinder #4 (closer to windshield) spark plug was still intact but the white part around the electrode was loose but still inside in plug. The plugs that I am running are Denso Iridium IK24

Today I did a compression test using the Actron compression tester from sears. This test was done DRY with the motor COLD. I did not want to risk putting new plugs in to warm the motor up. These are the numbers I came up with:

Cylinder 1 182
Cylinder 2 176 (worst looking plug)
Cylinder 3 215
Cylinder 4 230 (best looking plug)

Where should I go from here..... Should I do a leak down test???? Or should I just start to tear down the head and take a peek inside. Do I put new plugs in and see what happens??? I would also like to know how this happend and what its called. Any info would be helpful.

I can tell the motor ran very lean by the way the plug looked. I just filled up 10min b-4 it happened with 93 octane. Is it possible I got bad gas or gas with water in it????

MODS: (see sig)
Comptech S/C 5psi no ac (all comptech hardware FPR, EMS, etc......
Stock block and Head
DC Header
Spugen exhaust
That is all that is relative to the motor.

I'm going to get pics up of the plugs soon. Prob later tonight. I will also post more details tonight.

Thanks for reading
Kenny
ken_s2k@yahoo.com

Here are some pics of the plugs as promised.....
From left to right Is Cylinder 1-4


These 2 are cylinder 1 & 2

These are 3 & 4

Sideways

Plugs going like that are certainly indicative of pre-ignition. A bore scope would allow you to inspect the cylinder walls in one and two. Sorry to say, it sounds like a teardown and sleeve job in your future. On the bright side you can increase the size and drop the compression.

jasonw

With that much variance in compression, it sounds like the rings are bad.

mario_speed

Don't know if you have done the spark plug recall? but here is a link.

https://www.s2ki.com/forums/index.php?showtopic=275214

KenGPW

I agree with u there...... Lately I have been getting a lot of black on the rear of my car. Sometimes there is small oil drops also. My gass mileage is pretty poor. And I have to empty my small (Home Depot Special) catch can about every 400-500 miles.

Should I just take the head off tomorrow morning. Most likely I will just buy a new/used motor and drop it in. In the long run It would be cheeper then sleeving, rods, pistons, bore, bearings,.....etc. Plus I will prob have some bent valves at best or even a shot head. I know there is quite a bit of spark plug fragments floating around my motor or cat......

Hey Sideways....... Would you be willing to give me some info on your motor???? What sleaves, pistons, rods did u go with and who did the assm.. for u?????

Spoonie

Same exact thing happened to me. There were deep slashes in each of the cylinder walls. Total cost of rebuild $4700 dollars. That also included a Clutch job and completely new bottom end

S2KenC

Here's a thread awhile back that documents Iridium Sparkplug failures. The thread starter posted about Denso IK22s that failed.

https://www.s2ki.com/forums/index.ph...ic=326331&st=0

FF2Skip

I feel ya, KenGPW.

If you do not plan to go ahead and up your FI system, then I say just drop a new bottom end in, have the head looked at/taken care of and go.

If you had any plans of going larger, then I say do as Sideways suggested. Laskey Racing's bottom end build is around $3400, return shipping included. If you have time, I'd recommend that path. They also do head work(mine's enroute).

Any chance those plugs were regapped after they had been run in the engine for any amount of time?

Billman250

Dam.....this is the fifth engine I've seen in which the IK24's fell apart.

The number 3 plug was not tight enough plain and simple. A properly tightened plug will not back out.

As for the others, the pieces danced around in the motor and destroyed the cyl walls and possibly the valves/head.

I'm pretty confident you will be pulling the engine.

Do yourself a favor next time around, don't use those plugs anymore. I've seen them fall apart right in front of me with less than 100 miles on them.

Sideways

There are plenty of cars running the Denso Iridium plugs and boost with no difficulties. The pictures show what appears to be severe detonation. This is not the falt of the plug.

Earl Laskey has a good track record building bottom ends. His price is $3550 including shipping.