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Discussion Starter · #41 ·
Another question:

Since my current plan is, to pull off the left cylinder head and check/fix the valves (thinking of lapping them unless I find something more "nasty" in there), and leave the right side head carefully alone, is there any potential risk in doing so?

From what I've seen/read/heard, it's really the left one that has been "bothersome" statistically, and I figure with consistent compression readings (150psi) on the right side, it would fall under "if it ain't broke, don't fix it", unless I'm missing anything.

Please let me know if there may be any such thing :)

By the way, what is the "normal" compression value range for the Pentastar? Is 150 "perfect" or "so-so"?

Thanks!
 

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150 is a great compression for this engine. I would do just as you are saying and only pull the one with the issue.

If it were a failure from overheating, I'd do both whether they tested good or not. Reason is sometimes small leaks may only show up when the engine is warmed up.
 

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Discussion Starter · #43 ·
150 is a great compression for this engine. I would do just as you are saying and only pull the one with the issue.

If it were a failure from overheating, I'd do both whether they tested good or not. Reason is sometimes small leaks may only show up when the engine is warmed up.
Thanks, and sounds good! :)

Now when you say failure from overheating, do you mean like a blown/burned head gasket after losing coolant or something?
 

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Yes, if the engine hit 250+, bad stuff happens. It really doesn't like anything past 235. Thermal protection (engine limp mode) kicks in at 244. All that really sucks when you consider normal operating temps are 203-222.
 

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Discussion Starter · #45 ·
Hi everyone,

It's been a while and I wanted to give an update.

I had to find the right tools and the right time, and went ahead and pulled the left cylinder head.

It was nasty but could have been worse.
Audio equipment Automotive lighting Gas Automotive tire Auto part


Valve seats fine, just badly pitted exhaust valves, some of those having straight lines through the sealing surface, which can explain the leaks.
Automotive lighting Motor vehicle Automotive tire Automotive engine gasket Rim


#2 head, which was the worst:
Automotive tire Automotive engine gasket Motor vehicle Rim Circle

Automotive tire Alloy wheel Audio equipment Rim Motor vehicle

Automotive tire Rim Automotive wheel system Auto part Circle


Valve from cylinder #4 that was still running fine:
Wood Audio equipment Musical instrument Musical instrument accessory Microphone


From #2, the leaky one:
Automotive lighting Hood Bumper Automotive tire Automotive exterior

Door Rim Steering part Gas Automotive wheel system


So - valve lapping to the rescue:
Automotive tire Rim Motor vehicle Gas Automotive wheel system

Wheel Automotive tire Motor vehicle Rim Alloy wheel


The good news:
When I put everything back together, I only had 2 10mm bolts left over extra :D :D (looked like body bolts so I'm not super concerned).

But, more importantly, the car is now PURRING like a kitten, oh so nice and smooth!

THANK YOU ALL who helped me figure this out, its truly appreciated!
 

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That's some nice work. What compound did you use?
 

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Discussion Starter · #48 ·

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Discussion Starter · #49 ·
Sweet! Good to hear you got it fixed. Something hard must’ve been injected to damage the valve like this, very odd and unlikely for sure.
Thanks! And believe me, it's quite a relief (especially that I didn't have to "explode" the whole engine and it was something relatively simple).

You know, I was wondering myself why they pitted in the first place - if this is common or very rare, but in doing online search I did get the idea that (especially) exhaust valves do pit sometimes.

I don't know if I should bet my life on this never happening again, but I just do hope that even if it does, it will "leave me alone" for a good chunk of tiem before it does...

One thing I was wondering, if the original valve seat might have been a little too narrow to provide the valve sufficient cooling, and maybe that contributes to overheating and softening - not sure.

One thing that does seem strange, is that the right bank had no issues, and the left one had multiple - if something got in the engine, I'd assume it'd affect both sides. But I mean that's even a mystery to me, with the early (2011-2013) Pentastars dropping valve seats only on the left bank...
 

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I do know every time I take Pentastar heads in to the machine shop they replace all exhaust valves and seats. Never asked how common valve damage is, but they've told me they do it as a precaution because of the dropped seat issue. I never measured the seats before and after or asked about the process, so it may be that they bore them out slightly and put thicker seats in. I know the issue with them dropping is supposed to be due to the head getting too hot due to obstructed coolant passages around the valves (early heads).

Pitting could be from the valve sitting open during long times of non-use and developing condensation rust spots, or any liquid getting into the cylinder (oil, coolant, overly moist intake air). With your valves, the biggest head scratcher is that straight line. I have no clue what could have done just a single line like that and not scratched up a ton of other stuff along the way. Maybe a grain of sand on a spark plug during a change?
 

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Discussion Starter · #51 ·
I do know every time I take Pentastar heads in to the machine shop they replace all exhaust valves and seats. Never asked how common valve damage is, but they've told me they do it as a precaution because of the dropped seat issue. I never measured the seats before and after or asked about the process, so it may be that they bore them out slightly and put thicker seats in. I know the issue with them dropping is supposed to be due to the head getting too hot due to obstructed coolant passages around the valves (early heads).

Pitting could be from the valve sitting open during long times of non-use and developing condensation rust spots, or any liquid getting into the cylinder (oil, coolant, overly moist intake air). With your valves, the biggest head scratcher is that straight line. I have no clue what could have done just a single line like that and not scratched up a ton of other stuff along the way. Maybe a grain of sand on a spark plug during a change?
Hmmm, interesting...

From my online research so far, the seats on the early heads were softer - and working the ones on mine, I can definitely tell they are some hard a...s mofo's ;) (Not a lot happened to them vs the valves, while lapping) So to me it seems they could've well changed out the seats for harder types, after the early failing ones.

I also came across the datum that sand from casting molds would've stayed in and obstructed some cooling passages in the head, until I saw a post from a person that said they'd worked at the plant where those heads were made and sand was not used in their process... To me this is like going down a rabbit hole, trying to understand this stuff...

As for my car - I got it at a little over 1 year old, with 30000 miles, and now it's at 2 1/2 years old, with about 97000. When I pulled the plugs, they looked like the original ones (by their wear), so that scenario (sand in plug hole) is eliminated. Also, not a whole lot of standing unused for long periods, as I've been using the car regularly (the mileage should tell you ;) )

There was one, more recent incident, where the rubber boot of the intake pipe slipped off the throttle body while under way, and I drove it like that for maybe 20-25 miles (highway) before realizing what it was (the rumbling sound made me think something blew in the engine until I found it was the intake) and put it back on. So maybe (?) during that time something could've been sucked in to the engine and cause this? EXCEPT why only on one bank and not both? (Unless the intake manifold geometry might favor the cr...p going to one side vs the other.)

And all three cylinders on bank 2 had pitting, and both #2 and #6 had lines going through the mating surface (multiple ones), I just didn't thiink to take pictures of all of them (i.e. that line on the photo is but one of many). #4 only had pitting without lines.

Gotta love mysteries... It'd sure help my peace of mind if I knew WHAT I could DO to prevent such from happening... (Unless I can just get mentally prepared for regular head/valve overhauls, which seems a little excessive to me.)
 

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That intake slipping off the throttle body could have been it. Maybe there was some peculiar dirt/particles stuck to that intake tube and it got in as you drove.

Bank 2 may very well be the “favorite” side for heavier stuff. These intake manifolds are dry and not wet like carbureted ones, that is why spraying intake cleaner through the TB does not guarantee all valves to be cleaned equally.
 

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Discussion Starter · #53 ·
That intake slipping off the throttle body could have been it. Maybe there was some peculiar dirt/particles stuck to that intake tube and it got in as you drove.

Bank 2 may very well be the “favorite” side for heavier stuff. These intake manifolds are dry and not wet like carbureted ones, that is why spraying intake cleaner through the TB does not guarantee all valves to be cleaned equally.
That makes sense! Thanks!
 
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