Cracking spark plugs

So after wasting about $1500 trying to diagnose the issue here: https://www.mazdaspeeds.org/index.p...old-issues-still-haunting-after-rebuild.8988/ I figured my spark plugs crack for some reason. They crack in the coil boot area as you can see in this picture here:

I finally realised that when I noticed similar marks on the supposedly new spark plugs after I pulled them after about 800 miles and compared with the old ones which also stayed in the engine about 250 miles and were replaced just as a precaution because I didn't know what else to do.

So far this engine cracked within about 1200 miles from the rebuild:
- two spark plugs on cylinder 1;
- two on #2;
- one on #3;
- none on #4 (yet).

Since the sparkplugs look normal on the cylinder side I'm not sure if I can blame the heat or anything else, since they worked absolutely fine with the previous engine which was pretty much identical less the CS cam shafts and the Mahle 4032 87.5mm pistons instead of the 88mm pistons I have now.


So what's the catch here, why do they crack? I just threw in a new set yesterday and after a few pulls another one cracked.
The sparkplugs are NKG 6510, purchased from EdgeAutosport only, and judging by their aspect, marks, markings, texture and everything there is absolutely no chance they are counterfeit.

The spark plugs are installed with a spark plug socket, and I'm always careful not to lean sideways when torquing them. Also, it never happened before, it started happening with this engine only.

 

Since the only truly different thing is the CS cams, could it be that there's some weird vibration that is tearing them apart?
I'm using Crower springs but this is what I had in the past with the other engine, on OEM cam shafts though.

 

This is pretty crazy. Everything I read is saying it could be detonation but you don't seem to be having those issues.

 

Have you always used the same brand of plug? I wonder if they are a hair longer than other brands and that combined with the new pistons you may not have enough clearance. Also try a different brand. There was denso I believe that was notorious for cracking at one time

Did you deck the block when you chamged the pistons?

 

Someone help me out and circle the crack. I can't see anything on my phone

 

I actually just looked at my last set when I thought I was having blow out issues and one of them was cracked pretty bad on the cermaic. I was using NGK 4 pc Iridium IX Spark Plugs - 6510 LTR7IX-11. I will take a picture when I can. I didn't even know this was a thing to look out for.

 

what the fuck? try a different brand

 

Ok, went from bad to worse. Probably I just fucked up a 2000kms old engine.

 

There is a spring in the coil boot so if the spark plug is a bit longer, assuming it's not a lot longer, that spring will compensate for that.
As for the pistons... the spark plugs need to protrude quite a lot into the head to comein contact with a piston, Like an inch or so. It's not physically possible.

I thought about that. But the other decent brand is Denso, and the ITV22's used to crack (usually on the cylinder side) on stock cars with just a tune. I used them for a while back in 2012 while I had the GTX3071R... but I moved to NGK because some people reported these issues with the ITVs.

 

I didn’t realize this was a thing either but I haven’t had any issues with my plugs doing this so far (knock on wood). So I take it that it melted the strap as well as cracked, or is the strap in the cylinder? Lol

 

That last spark plug you pulled out looks like the strap snapped off from something like severe detonation.

Have you started tuning the new engine with the new CS cams yet?

 

I wish I took a picture of mine, but lately I noticed 6510 are really easy to crack, I cracked 2 sets already one lasted 50 miles the other is like 150, mine cracks worst than that tho, as in falling apart. BUT 3 out of 4 of my coil pack are using copper rod, and 1 is using spring and the spring still cracks the plugs, I used a motorcraft platinum forgot the part number its like $16 for the set and this didnt cracked at all but to test the 6510 again I just bought another set of 6510 and gonna see if they crack again this time before I finally try their "rethuriam!??!?!" new plugs

 

I was logging when it happened... KR was 0.7 during that pull.

Yes, it's that engine...

 

You know... some engine builder/tuner told me the same thing on a Facebook group (it's a good group, not one of those bull of BS).
I used copper rods in the past when I was having a problem and those sets did not crack with or without the coils modification. Actually back then I was changing these spark plugs at 15-20k kms. This started happening all of a sudden with spar plugs I purchased from Edge in the last few months or so.

 

This is the last set I pulled out when I was having issues. It is also cracked like this on the other side. Only one did this. I got mine from HERE

 

This is also something to think about.

Detonation Problems in Turbocharged Engines with Direct Injection
Some late model turbocharged engines with Direct Fuel Injection can experience detonation at low RPM following a cold start or after prolonged idling. The problem seems to be due to gasoline mixing with residual motor oil on the cylinder walls in the upper cylinder area. Many motor oils contain large amounts of sodium as part of their detergent additive package. When the sodium mixes with fuel, it forms a compound that can easily detonate when the engine is lugging hard under load or accelerating. The cure is to switch to a motor oil that contains less detergent, or less sodium in its detergent additives.

 

Ok, the engine is fucked. 2200kms from rebuilding it and like 6 WOT pulls.
I replaced the NGKs with Denso ITV22s and when one of these cracked they released a shot of porcelain inside cylinder #3.
Cylinder 3 probably lost most of its compression so about 700ml of oil were pushed up through the dipstick tube in the engine bay.


Even though everybody mentions detonation, I picked nothing significant during the pulls that I was able to make.
This is how the ITV22 looked like on #3, while on #2 it was perfect.


After replacing the spark plug on #3 the engine sounded kind of normal though:


I suspect the sparkplug cracked after this 5th gear pull but not during it. the engine ran perfectly normal until next WOT logging attempts about 5 minutes later.

 

That really sucks, sorry to hear that.

 

Revised Mazdaspeed NGK spark plug gap guide:




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