Cman01

They all looked good but #6 cyl. plug looked a bit darker than the rest of them and also showed oil residue on the threads



All the plugs looked like the left plug and cyl. 6 is the right one.

Heads were done 3 years ago by AHP at just under 18,600 miles when new plugs were installed, car now has 23,000 miles on it. I also just got it going about 3 weeks ago from winter storage if that has anything to do with this but then I figured they all should look the same and not just 1 cyl.

Tony

Unreal

You are correct and that definitely should require some further investigation. Time to pull valve covers, and possibly do a compression/leak down test.

Apocolipse

Wiggle wiggle time

MAD Matt

AHP heads....Only 5000 miles....Wiggle test.....Really ???? Make me wonder if "The Fix" IS the problem.

Cman01

That's what I was thinking and I haven't even gone to 5000 miles yet...…………..seems like any issue posted up on the LS7 and it's bad guides, fix the heads etc etc.

I'm scheduled for a retune in May at another shop. I sent the pic to the person doing the retune and I'm waiting for a response, meanwhile another friend of mine that has his own shop (general maintenance stuff not Vettes or specialty race work or whatever but he's a car nut just like me). He thinks possible running rich in that cyl but I smelled the plug when I pulled it out it didn't smell of fuel or whatever and my car doesn't burn oil at all. He also thinks a leaking injector can cause that.

I just did an oil change for this season and the Amsoil came out golden brown colour not even dark/black. I changed to Pennzoil Ultra 5W30 for this season.

I went for a drive this morning car runs nice and strong but after it cools down a bit I'm gonna pull that plug and have a look along with 1 other one to see how they compare.

edit: PM'ed Kohle with the pic we'll see what he says (if he replies).

Landru

Sub'd.

Apocolipse

Yes 5k miles. Its not an issue with the heads - its the CrN coating on the valves that can fail.

Other thing could be running rich...but 7 is typically lean. How is your bank 1 LTFT and STFT?

Cman01

^^^^no idea at the moment on the LTFT and STFT, the next time I drive it I can run my "Torque" app on my phone and have a passenger keep an eye on that while I drive.

Again CrN coating failing after 4600+ miles on done heads seem far fetched.

Just to confirm #7 cyl. is pass side second last hole in block correct? Is that cyl. known to usually run lean compared to the rest of them?

Apocolipse

7 is rear driver side. 8 is rear pass side.

And yes - the coating can fail in even less time than that.

Cman01

My bad...…………..change the bad plug to cyl. #6 not 7. The plug did come out of the pass. side second to last cyl.

CDNZ

AHP did the heads, which guides did you go with? What else did you have done? “Stock” build?

Cman01

I went with their regular powdered metal guides (not the moldstar version), heads are ported by them.

VR Kaotik cam, headers, Peak Speed radically ported stk intake and TB, 10% ATI, YT 1.8 RR.

Cman01

So I pulled out #6 and #4 to take a look. As mentioned earlier today I drove the car with the new plugs installed so basically did about 40 or so miles (maybe a bit more) mainly highway 70-75mph, some idling in traffic and minor city driving @ 35-40mph. Some decent acceleration not WOT.

Left plug is #4 cyl. (which will be like the others) and #6 is the right plug.



Again smelling the plugs after removing them I don't smell fuel and again it looks like obviously oil is somehow getting into #6 cyl. and making it's way past the threads onto the body below the insulator area of the plug.

Will probably need to pull the pass. valve cover to have a look...………………..maybe tomorrow.

corvettenutz

leaky injector? swap the injector and check it again

Apocolipse

Oil is straight giveaway its getting in somehow. Pull the cover and see if your seal is still on properly and give the valve a lil wiggle.