StealthFormula

iTrader: (35)

I recently took the car on a trip and when I got home I noticed that the two last plugs on each bank (cylinders 7 and 8) were carbon fouled. The rest of the plugs appeared either normal or whitish-gray. Plugs were Autolite 104's gapped at .040". Picture below represents what cylinders #1-6 look like:



Pic of cylinders #7 and #8 carbon fouled plugs:


Whether correlated or not my car starting to make a ticking noise at cruising speeds. The noise sounds more like a spinning type noise at idle. I have done alot of troubleshooting but have not yet found the culprit.

Today I installed new MSD wires and NGK TR6 plugs gapped at .038". I drove the car for five miles and then checked the plugs. Cylinders #7 and #8 are beginning to foul out and have white speckles on the ground electrodes while the remaining six plugs have extremely white ground electrodes. Pic below shows one of the white electrode plugs that represents cylinders #1-6 and the fouling out plug that represents cylinders #7 and #8:




FWIW the car runs without any type of hesitation and doesn't appear to be down in power. Thoughts?

ThreeHonks

iTrader: (10)

wow you are having some weird issues just like me.

My number 7 cylinder is extremely rich, but my number 8 is decent

RamAir95TA

iTrader: (2)

Just a thought, but did you use thread sealant on the rocker studs that protrude into the intake runner? I know you have LE ported heads...

StealthFormula

iTrader: (35)

Yeah I made sure to do that when I installed the studs.

It's weird because for two and a half years I never saw this with my plugs until now.

quik95lt1

iTrader: (7)

i ran into an issue like this and it was actually a leaking intake gasket......i was sucking vapor/oil from the valley into the cylinder..........just a thought FWIW

YodiBrodi

those 2 cylinders could either be burning more hydrocarbons (oil or fuel) than the other cylinders or the spark isn't hot enough or have enough duration. compression could be a factor as well since it too will affect the efficiency of a cylinder. egr valve might be able to contribute since when open it technically makes for a rich condition (less oxygen). egr port is at the rear of these IM's right? that's where 7 & 8 are. seeing your sig though i somehow doubt you have egr still on the car

AChotrod

iTrader: (17)

I would look into the IAC thing 96caprice mentioned.

StealthFormula

iTrader: (35)

I'll have to check that out, thanks.

Yes the EGR port is at the rear of the LT1 manifolds and it is long gone lol. I could perform a compression test just to eliminate one more possibility.

I thought about that after he mentioned it but for the 2.5 years I've been running my undrilled 58mm TB I haven't had this issue with the plugs. I've been thinking about doing the drill mod regardless but I am a little hesitant because the car idles perfectly and I have heard of people in the past performing this mod and having high idle issues so I'm on the fence right now.

StealthFormula

iTrader: (35)

I forgot to mention and just a thought...the car was driven at a constant 70mph for several hours if that has anything to do with the plugs looking how they do. Typically the car is driven short distances but driven very hard and the plugs always look clean. Maybe I need to take the car out and really beat on it and see how the plugs then look?