Misfire! P0306 - dropped valve seat!

Haven't pulled head but cylinder 6 is showing zero compression, and leak down test exposed air noticeably coming out through intake. All other cylinders showed 180-190 psi. This is my daily driver so just looking at rebuilt head to decrease downtime.
There's a pic in the first post of this thread of the 5 and 6 spark plugs and they look rich. With the scope the top of cylinder 6 was considerably black and sooty as compared to the other cylinders. I did email URD racing and Gadget did reply " I think it might be from oil from the PCV system getting into that cylinder and reducing the octane and causing knock. Just the way the PCV is setup and they way the engine leans back seems to flow right into that cylinder."

Anyways I should have heads off this weekend, I might as well do both headgaskets at the same time (I'm at 109,000 miles).

 

Im not famiiar with the ‘ UCON ‘tune......

at this juncture not knowing what exactly has the engine at 0 compression

does the UCON tune advise U of the amount of ignition advance it provides.................


‘ Knock / Detonation ‘ ( 2 different creatures ) could have contributed to the cylinder failures

 

Something about the tuning of the Injector Dynamics and the UCON, or X-1, did not play well together. Clarification would be needed for the UCON.

 

Do you have a catch can? Will help reduce carbon build-up.

How much boost were you running?

What RPM limit?


It does sound more like a bent or stuck valve/s. Hopefully that, and not a really damaged ring lands.

If it is valves, and you are running increased RPMs, the it may be time to upgrade the valve train.

Good choice stopping when you did.

 

Stuck open valves will be easy to spot, when you pull your Driver side valve cover, and rotate the engine a little.

 

Hey Torspd! I do have a catch can and was just under 8 psi. Wasn’t foot to the floor but got up to5k rpm. Nothing started happening until I was slowly decelerating that’s when the shaking started.

 

What kind of progress have you made?

 

Hopefully start tear down tomorrow. By the way I came across another post about you using the 12mm snap on head bolt tool vs the 10 mm. You still swear by the STSm12E bit?

 

Only every used it and only ever knew about it, until that thread which you speak of.

Years ago, that was what came up as the part for the Toyota head bolts, when on the Snap-on truck.

I cannot say that the other will work better, or if there is a better tool. I just know that mine works.

 

sounds like a valve spring went south

the engine has enough clearance for the valve Not to strike the piston ( normal )

unless the spring split/broke allowing it to strike the piston resulting in a bent valve

 

Try a borescope, might see a bent or stuck valve. Doubt it's possible with a timing chain, but I had a timing belt skip teeth before causing a whole bank to misfire.

 

Took me last two evenings after work just to clear out the garage to make room to work LOL!! Got the charger and most of the top stuff off and I can clearly see down cylinder 6 intake runner and valve is stuck open, all other valves closed - couldn't get a clear picture with phone. Should have water pump and timing stuff off by end of day - so if I can find locally the special cylinder headbolt driver socket then heads should be off no later than Monday. Some side notes : seemed to be a lot of blow by oil in supercharger and intake runners - I do have a oil catch can though.

 

Looking at the cam for that valve, is there any obstruction on the top side?

 

stuck valves are unusual

not sure of the engine consistent operating environs

excessive piston blow by

leaking valve stem seal having given up

or both

 

So been doing what I can the last 3 days, my snap on head bolt bit arrived late this afternoon so that's a plus. Nothing on top side of cams show blockage or broken spring - heads will be off soon. Timing chain was nice and snug and main tensioner #1 showed no signs of extension or wear, small light scuffs on chain guides. I'm at 109,000 miles and 85,000 of those were with supercharger. Would you guys change all the timing stuff out at this point? Taking my time and blessed that I have not had any problems, issues, or broken bolts LOL! Here's some pics of progress:

 

Looks like time to pull the cams then.

 

something is holding the valve off the seat..............

if ALL the valve gear is OK .............something mightily strong would be to resist the spring closing the valve

UNlikely the valve will be reusable be certain to ‘ V ‘ block the valves when U inspect them

clear photo of head B4 !! disassembly

take close up of head at combustion chamber#6 !!!..............real close

maybe U can see whats holding valve open

 

Maybe a bent valve

 

Something valve related. Called it. Lol. I think you are the third (maybe 4th guy) of us blower dudes who has damaged something in the valvetrain. It makes me wonder the integrity of these valve setups as a whole now.