NGK plugs cracked porcelin

[misfitsfreak81]

Just wondering if anyone has had issues with NGK plugs cracking the porcelin in an SR20? Ive had 3 sets of plugs do this now. usually only one plug out of the 4 and not in the same cylinder. the porcelin is cracking to the point of it causing the plug to misfire. Its happened to both regular copper NGK'S and Iridium plugs. Ill try to post some pics later tonight or tomorrow.

Mike
North Shore Performance Auto and Fabrication

[Sileighty_85]

never heard of this.
Possibly Very high EGT's

[ultimateirving]

You're overtightening them! stop it

[4x4le]

I use ngk copper plugs exclusivly and have never had trouble with them in my srs kas or cas

[misfitsfreak81]

thanks for the input guys. as far as high egt's i supposed its a possibility. i should have been more clear as to which part of the porcelin was cracking. its the upper section that is inside the boot of the coil, not the part thats in the combustion chamber.

Im sure im not over tightening them, im a stickler when it comes to following torque specs. they have always been torqued to factory service manual specs.

Ive heard from some others in the industry that NGK is producing some of their plugs stateside and some in japan. apparently the japanese ones have supperior porcelin due to less strick manufacturing restrictions. just a thought though, i have no 100% way to confirm this.

Mike

[4x4le]

How quick are they going bad? I replace mine more often that necessary out of habit. What heat range are you running? A function of the plug that most people dont consider is that they are to help cool the combustion chamber. Maybe not enough heat can excape which why people are asking about egts. You may need to step 1 or 2 cooler

[misfitsfreak81]

they are going bad about every 3-4k miles. Im sure i could go a step colder and not have any issues. however the spark plugs dont act as heat sink the way you mentioned that they do. not to any messurable (without extremely expensive equipment) amount at least. the function of the different heat ranges is for identifying the ability of the plug to absorb heat from combustion without creating a "hotspot" in the combustion chamber.

Im going to try one step cooler next time i change them out. i had an extra set laying in my tool box luckily so i just popped those in while waiting for the other set to hopefully be warrentied.

Mike

[4x4le]

how is that different than what I said. I know they are not for controlling egt's but other than hotspots what would it even matter the temp of your combustion chamber? Youll have hotspots long before your worried about melting valves.

[army240]

I'd say the heat range is wrong too, try that first and keep us inform on the results.

Frank

[misfitsfreak81]

how is that different than what I said. I know they are not for controlling egt's but other than hotspots what would it even matter the temp of your combustion chamber? Youll have hotspots long before your worried about melting valves.

agreed. i just re-read my response and realized that i basically just re-stated what you had said in another way. so i do believe im gonna go a step colder next time i change plugs and see if that makes any difference. ill keep this updated.

Mike

[4x4le]

wait, I just re read it again and I do think were on a different page still. They actually do act as a heat sink. they wont turn into a hotspot if they take too much heat out. The only reason you dont run as cold of a plug as possible is because it wont stay hot enough to keep its self clean. It wont become a hotspot itself unless its too hot of a range of plug.

wether or not were on the same page no biggy. just more food for thought as far as whats going on inside and what their function other than sparking is.

[Almasxxx]

detonation problem knocking piston and cracking need check crank timing