So long story short I was planning to pull the head due to some oil leaks I was having. In doing so I was interested to see how the valvetrain and pistons were looking since I last pulled the head 10,000 miles ago. Below I've attached some pictures that I would like some opinions on. I have been having some issues with partial throttle knock and am interested if some of these teardown photos can give a hint to why. IE too much carbon build up. Note that in trying to diagnose this issue I ran 5 gallons of 110 leaded fuel through the tank about 300 miles ago (car still showed the random knock) so this may have some effects on the colors of the parts. Any other comments on what the parts are showing is much appreciated.

Picture 1: Exhaust valves. Valves themselves certainly look white, I'm assuming this is b/c of the 110 leaded fuel. The white flakes are brittle and rub off if I touch them, also from the 110?

Picture 2: Another cylinders Exhaust valves. Looks like one of my stem seals has bit the dust? I used a socket to tap them on, so maybe an install issue on my part? I noticed this on two other exhaust valves (intakes are good). The ones with a leak have less or none of the white flakes.

Picture 3: Overall shot of the cylinder head, noting some white speckle patterns around plugs in cylinders 2 & 3. See pic 4 for a closeup

Picture 4: Close up of combustion face on cylinder 2 (or 3). Note the speckles, is this from the 110 or signs of detonation?

Picture 5: Block/Piston tops at "2013" teardown. seems like a lot of carbon build up for 10,000 miles, reference picture 8 for same picture at "2012" teardown.

Picture 6: closeup of piston, is this carbon build up excessive? Could it be causing a hot spot thats giving me pre-detonation ?

Picture 7: closeup of the scale/build up on the piston. There was a mix of the soft build up that would scrape off and then this hard build up that would chip off.

Picture 8: Block and pistons from "2012" teardown, sure is alot less carbon (miles at this point was 60,000)

Picture 9: Closeup of piston from "2012" teardown for reference.


Below is a little history from the "2012" teardown.

The head was pulled at that time due to low compression in one cylinder, due to a valve not seating. While the head was off I went with all new supertech nitrided valves, manganese bronze valve guides, and supertech stem seals. I also had the head decked at this time. Kept the stock cams and used the oem MLS head gasket with some ARP head studs torqued to 80 ft-lbs per the instructions that came with them. (this time some 272s will be going in )

Beyond the info in my signature, AFR basically tapers from 11.5 to 11.0 from the time of full boost to redline. Cruise afr is still done by the O2 sensor and shows up on the gauge fluctuating high or low of 14.5.

 

Rest of the pictures

 

No one? I figured everyone likes pictures!

 

Some oil needs to get past the valve seal to lubricate the valve stem. Therefore, I wouldn't be too concerned unless the valve can wobble in the guide. You have to have the spring off to check for this.

 

2 and 3 look a little leaner, have markings on the head past the plug as well as clean pistons. Have you had the injectors checked? 1 and 4 actually look pretty close for pumpgas. Oil past the valve guides wont cause what we are seeing though.

 

Agreed, however it seemed b/c I can see a visual leak it might be a bit excessive on the amount of oil allowed past? I already ordered some more seals, I think while the head is off I'll go ahead and replace the 2-3 that I could visually see leaking.

I'll check the valve movement while i've got the springs off. Got a good recommendation on how to decided how much is too much movement :-) ?

 

Hey John, thanks, just what I was looking for. I've always been suspect of the injectors and actually have a spare set already on hand for this "rebuild". I must say I havent heard too much about stock injectors running pump gas fouling up, but then again I'm still learning. Think it's worth having the used set cleaned/flow tested before I put them in?

When you say "markings on the head", I assume are you indicating that the white specs are signs of detonation on the head?