Misfire! P0306 - dropped valve seat!

point taken

how much ‘ boost ‘ ?!?!?!?!

we have found if boost exceeds the spring.............................

the valve is held offf the seat resulting in dinging the piston = bent valve

again how muc B O O S T actually measured ??

 

2.5 should peak around 10 lbs or maybe a smidge more at sea level

Good work so far OP! Keep after it, i'm rooting for you. It will feel great once you get the issues sorted and put it all back together again

 

stock engines out of japan run minimal seat pressures...............many times less than american engines

some weve measured in the 30’s................under boost we had to increase the springs

no less if U are saying 10lbs boost

i actually asked for MEASURED Boot..........NOT Conversational boost

common mistake when talking boost weekday hhoters guy disregard Normal atmospheric Pressure ( Aircraft guys NEVER would )

thats Another ‘ BAR ‘ or 14pounds

 

Just googled “V” blocking. Got to do some reading.

 

With my catless exhaust and at sea level I was just under 9 psi on boost guage.

 

machinists use ‘ V ‘ blocks to determine if a rod is straight & round.............only takes a minute

with the stem n the block

turn the valve will show if the stem is straight & round

if the stem is bent or warped it wont roll correct in the ‘ V "

no less if the head o valve is 90 degrees to the stem

if the head is bent .......the stem straight........the head will wobble

if U have a machinist friend it shouldnt amount to more than a beer to check a few

 

in fact at 9psi Ur only recovering the losses of the engine

stock cams U should have seen almost equal gain torque & HP

with a turbo more HP near redline

the 99% mistake

at sea level its 9+ 1 bar corrected !!!!

typically rule o thumb IS 14-15 psi so its really 24 psi................doesnt have to be minutely correct

technically it changes at elevation no less actuall weather barometric pressure

always remember its boost +atmospheric ..............get it

on 1 of our normaly aspirated race engines the valve springs were stock only 35psi

after building a turbo DOUBLING ( stock cams )the HP 55s were necessary

had to put in 55s or the boost would keep the valves slightly open

 

Anyone know what size chase to clean out headbolt threads?

 

11mm. Can't remember the pitch. You have the bolts though. Double check

 

According to Felpro and ARP required thread chase should be 11mm x 1.5 pitch.

 

Got the heads off and looks like the #6 intake valve seal got pushed or sucked down and is keeping the intake valve open. All the intake valves were pretty black and gunked up on both banks. Original head gaskets were intact so no failure there. Also some black soot showing I may have had small exhaust leak coming from #6 exhaust port on back side of thorley long tube headers. Here's some pics of heads and valves:

https://photos.app.goo.gl/ZGK4VgdiHHxKntBp6
https://photos.app.goo.gl/9MsJnN2N6ziTwZoH7
https://photos.app.goo.gl/sPfvBPBJ34UGBMwz9
https://photos.app.goo.gl/An27ASrsXCGEU4CY9
https://photos.app.goo.gl/FjiQcuq36ozeMBd3A - this last pic you can see the seal sticking out.

 

commenting on the obvious

on ALL the photos the engine is running several factors Rich in each cylinder

no less there is quite a consistent bit of ‘ blow by ‘ piston rings ALL cylinders

resulting in widespread / excessive carbon buildup in ALL combustion chambers/ ALL cylinders

while IM not the arbiter Iv NEVER seen the extent of blow by & buildup in ALL cylinders B4 ever

hard to believe there good compression numbers present

no sure how the engine was NOT exhibiting bad running low speed running

+ compromised mid range

that last photo truly brings it home

U mention it as a ’seal ‘..........................??? is it NOT the valve seat ?

strangely enuf no extensive damage has been done ( closer examination i cant assess= im not there )

if it is Undeed the valve ‘ seat ‘ it might be repaired seating IN Another ( maybe )

if not another head............all cylinder cleaned up no less be certain straight = new rings

possible bottom end NOT harmed

decrease fuel to air ratio......................raw gas is washing the cylinder walls contributing to ‘ blow by ‘ !!

resulting in excessive carbon build up

 

Yeah, engine seemed to be running perfect just before all this, my A/F guage seemed to be showing proper A/F ratios. My tune even runs a little lean when highway cruising on purpose 14.8-14.9. I'm new to dealing with cylinder heads so It does look like it's the valve seat that is sticking out. All piston cylinder walls were unscored and clean (probably washed out like you said).

I am running a 7th injector system that shoots fuel down the intake of the supercharger which should only turn on if I'm going wide open throttle - but hardly ever run the truck that hard. I don't have a way to tell when it goes on. Will update once shop checks heads for straightness.

 

You are correct. Valve seat. First time that I have ever seen this as well. Intriguing.

If the head is not damaged, a new valve seat may be all that is required.

 

Just look at the 7th map? I have a 3.4 with the same setup. Mine starts at 4psi and 3000rpm. But you’d have to pull up your map.

Anyway. Everyone always talks about what AFR should be WOT (~11AFR-11.8) But it’s never clarified if that is the entire rev range of if it should ramp from closer to 14 at lower RPM to the desired AFR at redline

Because we’re supercharged and heavy load is going to give you mostly max PSI all the way from low RPM to redline what should we be aiming for throughout the rev range?

 

‘ engine seemed to runnin perfect just before all this ‘

ok this where we differ...............................................

the initial photo of the 2 spark plugs DID NOT LOOK GOOD

that engine IS WET !!!!! the Tune ( ?????) Is W A C K !!!

its been decades since Iv seen that much carbon build up in a cylinder let alone ALL 6

EXCESSIVE FUEL + EXCESSIVE BLOW BY + SLOW RUNNING

putting it back together under the best circumstances aint good

 

I assume you mean I should also tear down the block at this point.

 

What about those plugs look so bad?

 

Your only problem was the valve seat. Unless your desire to build the block is nagging you since you're in there, stick with fixing the head.

Since you are in there, this is the perfect time to upgrade the valve train components, if you have the time. Springs, valves, retainers. Once a machine shop determines if that recessed area around the seat is OK or not, you'll know what you need to do.

It all comes down to your time frame and budget.

 

from my very

from my very 1st response I knew there were other major issues .................

U say it was running ‘ perfect ‘

‘ blow by ' works in BOTH directions which means Ur crankcase oil was severely

contaminated

if i had a shop & put out work like that the mob with pitchforks would leave frankenstein alone

both heads are bummed up excluding consideration of the valve seat

if i were to put it back together FREE I would NOT on the suggestions already made

I can see plainly whats WRONG with Ur engine

U are likely to be satisfied just to get back on the road

show photos of both heads in current conditions to good mechanics

it would take shop time just to clean them up

suggestion.................if thats ALL U truly intend to do

BE CERTAIN ALL disassembled parts go back IN EXCATLY where they came from

thats EVERY nut / bolt/ screw / washer/ valve & springs

good luck