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2010 3.6L LLT - not your typical engine problem.

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  • 2010 3.6L LLT - not your typical engine problem.

    Hi all!

    New guy to the site. Googling the net for information on the 3.6L LLT engine led me here. With so much confusing information on the web these days, this site seemed to be very informative with its answers ... so here I am! The vast majority of my engine building experience has been with old-school carbureted pushrod operated V8s. So this overhead cam computer controlled LLT V6 is all new to me. I need some help from those that have worked on this engine for a while ... that's where you guys come in!

    A little background on my current project. I recently picked up a 2010 Synergy Green Camaro LT with the 3.6L LLT and a 6 speed transmission. The previous owner bought it with a blown engine that ultimately seized. He bought a remanufactured "long block" from Advanced Auto Parts and built by Spartan Engines of Texas for them. He took the remanufactured long block and the car to a shop where they pulled the blown engine, swapped the necessary components over to the new long block and then reinstalled it into the car. Previous owner stated that the car ran fine for the first 19 miles and then started to run like crap. He took it to a different shop, and they discovered that it had bent a #3 exhaust valve and tossed a rocker arm. Previous owner got into a big pissing match with Advanced Auto Parts and the shop that installed the motor with each blaming the other for the engine failing after only 19 miles. After getting nowhere with Advanced Auto Parts and the installation shop, the frustrated previous owner decided to wash his hands of the whole mess and put it up for sale. This is where I came in. It has a little over 100K on it and a sick motor, but the Synergy Green and the price was too much for me to resist. So I bought it and am now doing "forensics" on it trying to figure out what happened to the engine.

    I pulled the engine and completely disassembled it down to the bare block. Here is what I found. As stated, the #3 engine bent an exhaust valve for some reason? When it bent, it wouldn't fully close and that created enough slack for the rocker arm to pop off. But why did the valve bend? Camshaft timing was perfect. There is no evidence of the cam timing being incorrect or of the valves hitting the pistons. I could not find any evidence of any foreign object being in the combustion chamber and jamming the valve. The surfaces of the pistons, valves and combustion chambers are clean and damage free. Oddly, I did find a small bit of oil on top of the #3 piston. The cylinder, combustion chamber, valves and spark plug all had a fine layer of oil on them. Perhaps since this cylinder wasn't firing (due to the massive compression leak through the bent valve) there wasn't any combustion pressure on the rings allowing some oil to slip by? I removed the piston to check for ring damage and found none. Oddly this engine has two pice oil rings (instead of the traditional three piece) oil rings installed - a spiral oil spring inside of a one piece u-shaped tension ring (never have seen one like that before)? All of the other five cylinders and pistons looked okay and like they had been firing, although a little on the rich side (perhaps trying to compensate for the badly misfiring #3?).

    Searching for something, I finally found a potential culprit in the intake plenum. When the original engine blew and seized, it apparently had a catastrophic piston failure. Very small parts of the failed piston blew back up the intake runner and collected inside of the intake plenum. Apparently the installation shop never bothered to look inside of the plenum. They just removed it from the blown engine and transferred it to the new one. I theorized that it may have been possible for a piece of the failed piston inside of the plenum may have been sucked into the #3 cylinder and somehow got jammed in there bending the valve. However, as I said before, I could find no physical damage to the piston, valve face, valve seat or combustion chamber. I would think that if a piece large enough to bend a valve got in there, it would have left some telltale evidence in the form of nicking or gouging the surfaces in there? So even though my theory is plausible, I don't think that is what happened.

    I'm really stumped on this one. I can't figure out what caused just that one valve to bend and then left no evidence other than the bent valve itself? I was really hoping to find the "smoking gun" before I start to put this engine back together. Maybe it was just a cheap quality valve used by Spartan Engines? Excessive valve guide clearance allowing the valve to "wander" on the seat? I just don't know at this point.

    So, if any of you experienced 3.6L LLT engine builders out there have any insight as to what may have happened, I would sure like to hear from you! Thanks in advance for your time and help!

    Cheers,
    Tom

  • #2
    Welcome! Not a lot of people around but maybe I can help. How bent is the valve? 19 miles on it means it wasn't bent from the rebuilder, and only 1 cylinder means the timing is fine. How does the guide and valve stem look? Valve spring is good? There really isn't a hell of a lot that this can be, and if there is trash in the plenum, you have the most likely source of the problem.
    Ben
    60DegreeV6.com
    WOT-Tech.com

    Comment


    • #3
      Thanks for your reply Ben.

      "Not a lot of people around" ... on this site?? Really?? I was hoping that I would find a lot of V6 experts here ...

      Yeah, this one has me guessing. I like the theory of some foreign object from the plenum getting sucked in there and bending the valve ... but only if I could find some tell-tale marks of it being in there. As I said, I could not find any nicks or gouges ... anywhere. Here's a few pics of what it looked like when I took it apart. I shone a flashlight in the exhaust port and you can see the crescent of light around the bent valve. In the vertical picture of the combustion chambers you can see that the affected valve is bent in towards the other exhaust valve. There's a pic of the cylinders with the pistons still in them. Somehow they seem excessively carbon'd up for only 19miles?? Lastly, there is a picture of what the inside of the plenum looked like showing all of the garbage left in there.
      Last edited by RzeroB; 10-04-2024, 06:42 PM.

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      • #4
        Aluminum is softer than steel, so it will just bend a valve and be on its way. If the piston is good and the bearing on that rod is good, then it looks like a new valve and check that it holds vacuum might do it.

        Most of the people who were on here are now on facebook. I have no idea who might still read the site, but I see a handful of people join every week so you never know. Might get some more VVT DOHC owners active on here.
        Ben
        60DegreeV6.com
        WOT-Tech.com

        Comment


        • #5
          I'm still in here every so often. Even though I haven't owned a 60V6 in probably 10 years. But, against Ben's wishes, my next one will most likely be the 3.6, albeit the twin turbo out of an ATS. So I'm keeping an eye on this one...
          -Brad-
          89 Mustang : Future 60V6 Power
          sigpic
          Follow the build -> http://www.3x00swap.com/index.php?page=mustang-blog

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          • #6
            Thanks for the replies. I have considered just installing a new valve. However, the presence of the oil in just that one cylinder concerns me. In addition to not being able to pinpoint the cause of the bent valve, I also can't pinpoint the cause of there being oil in just that one cylinder? The two are somehow interrelated, but I haven't been able to conclusively figure it out. I can't figure out how it got there? Maybe it came up past the piston rings, or down from the valve guides? How is the valve guide clearance measured? I'm reading of a technique using a micro dial bore gauge and a split ball gauge? In the past I would use a dial indicator to measure the lateral movement of the valve stem. That's all I have to work with without buying some new tools, wonder if it is still relevant?

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            • #7
              At one point I found the complete specifications for the 3.6L LLT engine on this site. Now of course when I'm trying to relocate it ... I can't find it. Can someone point me to it again ... please. Thanks!

              Comment


              • #8
                I swear it's on here somewhere, but I can't find it either. It should be here: https://www.60degreev6.com/vb5/artic...nt-dohc-vvt-aa
                -Brad-
                89 Mustang : Future 60V6 Power
                sigpic
                Follow the build -> http://www.3x00swap.com/index.php?page=mustang-blog

                Comment


                • #9
                  You would measure the side to side movement of the valve rather than the guide itself. They typically don't wear straight in the guide, and the hourglass (best way I can picture it at an extreme) is in the direction the rocker arm pressed on the valve. What you could do is pull a good valve and see how it feels in its guide, and the guide with the bent valve. If its not the same, then it could be the guide.

                  If it only has 19 miles on it, perhaps that cylinder didn't have the rings broken in good yet? I don't know where the oil is in the pics.
                  Ben
                  60DegreeV6.com
                  WOT-Tech.com

                  Comment


                  • #10
                    Thanks for your reply Ben. It's kind of like the chicken or the egg paradox - I don't know which one came first - the oil in the cylinder having something to do with the valve failure, or the valve failure having something to do with the oil being there? The best theory that I can come up with is the valve failed first, then with no compression in that cylinder there was no combustion, with no combustion there was no pressure on the rings and with no pressure on the rings, then as you said, the rings in that one cylinder were not broken in? As I said, it's just a theory.

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                    • #11
                      Oil isn't going to bend a valve, nor are you going to see that much oil going past a valve stem seal in 19 miles. You would see it in the intake port, not the exhaust. Without cylinder pressure, the crankcase pressure could push oil past the rings much easier. I can't think of a scenario that oil bends a valve.
                      Ben
                      60DegreeV6.com
                      WOT-Tech.com

                      Comment


                      • #12
                        Thanks Ben, I would tend to agree with what you said. I think I'm going to lap-in two new exhaust valves and see where I'm at. I don't have a flow bench so I can't vacuum check the valves. Thought I would leave the cams out, temporarily reinstall the heads on the block and do a leak-down check to test them instead. Now I just have to find the specs for how wide the seat to valve contact area needs to be ...

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                        • #13
                          Valve job machines have a vacuum checker built in usually to check the work. I made my own that uses an air compressor as a source.



                          Take that apart and use the black piece inside, with some threaded pipe and a vacuum gauge.

                          These plates have a closed cell foam applied for an exceptional seal. Several sizes available. Replacement parts and accessories sold separately.


                          Stick one of these on the end to see up the intake/exhaust ports.

                          Click image for larger version

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                          Ben
                          60DegreeV6.com
                          WOT-Tech.com

                          Comment


                          • #14
                            I'm not sure I'm following Ben?? Take the air pump apart, modify it with some threaded pipe and a vacuum gauge and put a Goodson foam pad on the end to see up the ports?? Maybe I can find a YouTube video on what you are trying to tell me?? Thanks!

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                            • #15
                              Click image for larger version  Name:	LLTSpecs1.jpg Views:	0 Size:	178.5 KB ID:	427496 Click image for larger version  Name:	LLTSpecs2.jpg Views:	0 Size:	189.2 KB ID:	427497 Click image for larger version  Name:	LLTSpecs3.jpg Views:	0 Size:	198.0 KB ID:	427498 Click image for larger version  Name:	LLTSpecs4.jpg Views:	0 Size:	226.5 KB ID:	427499
                              Last edited by SappySE107; 10-10-2024, 12:24 AM.
                              Ben
                              60DegreeV6.com
                              WOT-Tech.com

                              Comment

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