2003 Jeep Grand Cherokee Overland Build

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JimBill

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Well, I've been holding off making this post because it's both embarrassing and humbling, but here it is: I f@wked something up real good. I got it all back together mechanically (front clip still largely off, starting the winch install) and got fluids in it and went to give it a test fire. I was in the car, but a buddy helping said he heard at least 2 *bad* metal to metal sounds as it tried to fire and died. We confirmed we were getting fuel and spark, so I did a compression test and the driver's bank of cylinders were fine... passenger bank was 0... like needle not even wiggling. To be dead zero a valve basically has to be hung (timing being off a tooth or two would just make it have poor compression generally). YAY. I got a borescope in there and confirmed bent/hung valves. No good deed goes unpunished, and this is what I get for changing the timing set that was perfectly fine.

So WTF went wrong? Honestly I don't know. I ordered a reman longblock yesterday (which includes some improvements to address known 4.7 flaws) and once it comes in we'll rip this one out and pull the valve covers and front cover and such and figure out what happened.

During the course of working on it I had several friends helping. For the T-set portion I had a buddy who is a professional mechanic helping every step of the way. We triple-checked everything and if you scroll back you'll see we got pictures of every single timing mark in the right place. We cleaned, loctite'ed and torqued every bolt to spec. I even had a 2nd professional mechanic friend (20+ year master tech w/ Lexus) stop by before the front cover went back on and he verified everything.

All I can think of is something in the new timing set let go. I'd like for that to be the answer so I don't have to blame myself so much... but it just doesn't make sense. For the valves to bend as badly as they did the timing had to be WAY off so I don't think it "jumped a tooth" (plus chains don't usually do that, that's more of a timing belt thing). Not to mention, we rolled it over multiple revolutions by hand successfully with the front cover and valve covers off before we put any of that on. Turning it by hand we would have felt/heard piston to valve contact (we had the spark plugs out so it'd roll smoothly specifically so we could feel for any issues). Something had to have let go... and I just can't fathom why, other than I must have been a horrible human being in a past life... my CARma sucks.

I'll follow up with my usual pictures from what got done, but I had to put that out there first...
That simply sucks. But don't forget you are in good company because many (and I'm no exception here) have had similar experiences.
Be grateful there was only mechanical carnage as a result.
The expense in time and money hurts for sure, but you are deep into hobby you enjoy and you can't take the money with you.
Just this weekend working on the old 76, as I troubleshooted a 2 year old remanufactured carb (I paid handsomely for it) which components literally fell apart inside the fuel bowl....

I had to tell myself "this is supposed to be fun dammit!".

Now just scale that up to a long block.....
 

tjZ06

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That simply sucks. But don't forget you are in good company because many (and I'm no exception here) have had similar experiences.
Be grateful there was only mechanical carnage as a result.
The expense in time and money hurts for sure, but you are deep into hobby you enjoy and you can't take the money with you.
Just this weekend working on the old 76, as I troubleshooted a 2 year old remanufactured carb (I paid handsomely for it) which components literally fell apart inside the fuel bowl....

I had to tell myself "this is supposed to be fun dammit!".

Now just scale that up to a long block.....
Thanks for the kind words, and you're certainly right. I just keep looking back at all the pics and trying to figure out what went wrong - everything checks out in the pics (all grenade pins pulled, all tensioners and guides in the right places, all timing marks correct, etc.). I really want to think something just broke, which would make no sense but strangely would make me feel better.

-TJ
 

tjZ06

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New motor arrives today. I guess we'll find out WTF happened this weekend when we pull the covers and whatnot off the old one.



-TJ
 

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1581381964581.png

Motor came in today (and my buddy who's been helping me work on it's new Snap On boxes - all 4 of them, they're worth a loooooooooot more than my old WJ lol).

-TJ
 

TJDon

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HOLY COW MAN!! What a soup sandwich! Sucks about the engine. It’s been a while since I’ve gotten a chance to catch up on your wj stories. I’m curious as well of why the heck the valves decided to go crooked.
wondering if a rocker arm got cockeyed? I was a Jeep tech for 25 years and seen some crazy unexplainable stuff also
 

tjZ06

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HOLY COW MAN!! What a soup sandwich! Sucks about the engine. It’s been a while since I’ve gotten a chance to catch up on your wj stories. I’m curious as well of why the heck the valves decided to go crooked.
wondering if a rocker arm got cockeyed? I was a Jeep tech for 25 years and seen some crazy unexplainable stuff also
I thought about the rockers too, since we had all those off to do the HLAs. I *guess* it could just be pure chance that only the passenger side rockers popped off and maybe one got hung-up in a valve spring on each of the dead cylinders keeping the valve open, forcing the piston to bend them. But what are the odds one bank has that happen, the other doesn't? Plus, we turned the motor over by hand a few times after the HLAs to ensure the rockers were properly seated for exactly this reason. I just don't get it... but might know more this weekend!

-TJ
 
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tjZ06

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I was wondering why you've been so quiet in the group text. I'm sorry man. :(
Yeah man... this is a tough one. I'm not even sure what I'm hoping for when I get it open: something I did wrong or something that just failed. For the rest of the group, JCWages and I were in a LT1/LS1-based (and later LS2, LS6, LS7, etc.) based car club for a decade or something back in the day. We both had 4th Gen Fbodies then C5 Corvettes (and later a LM7 I think it was pickup for JCWages... with boost). Between my own stuff and friends' cars I've probably done 20+ LS cam swaps, and a dozen with heads too. I still ran LS's in my sand rails 'til just 2 years ago, so I had plenty of wrench time on those two. I never had one issue with ANY of the cam swaps or anything. Now, granted the timing set is WAY less complicated, but the principles are the same, and on some of the LS-stuff we actually degreed the cam and all of that. I've built the bottom-end on small blocks too, though never an LS. Anyway, point being I might be a bit rusty but generally have an idea what I'm doing, and called in a friend (two actually) that's a pro for the important parts: the timing set and HLAs.

So, it's still entirely possible we screwed up. Or, I'm just the (un)luckiest guy on earth and something in the brand new timing set broke.

The lesson here: if your 4.7 timing set looks good with no deep grooves in the guides and no discernible slop... leave it alone! ;)

-TJ
 
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JimBill

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I thought about the rockers too, since we had all those off to do the HLAs. I *guess* it could just be pure chance that only the passenger side rockers popped off and maybe one got hung-up in a valve spring on each of the dead cylinders keeping the valve open, forcing the piston to bend them. But what are the odds one bank has that happen, the other doesn't? Plus, we turned the motor over by hand a few times after the HLAs to ensure the rockers were properly seated for exactly this reason. I just don't get it... but might know more this weekend!

-TJ
My bet is on something weird with the lash adjusters causing a cam follower issue. I can't see how two side by side valves could get hit with a timing chain issue. With the small oil passages in the 4.7, maybe the adjusters didn't bleed or pump up quick enough and spit the follower. I've soaked enough SBC lifters in my time and primed oil systems, but this is a different beast and I can't say what is the right thing to do on assembly.
 

tjZ06

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Took it to my buddy's because the picker, engine stand, etc. etc. all were there so it just made more sense. Plus his tools are there and he's just more efficient there.

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Got started working on it today. New motor:

IMG_20200215_142945.thumb.jpg.397bee9a402f97425f7bd4689ae7a16f.jpg

IMG_20200215_142951.thumb.jpg.e0550b52d7361d2acadb3eee40bed713.jpg



Got the old one out:

IMG_20200215_143002_MP.thumb.jpg.413cea2619671b6cd0bef3acd829b3c9.jpg

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Unfortunately, I didn't think about the fact that we need a specific puller for the ATI, so that blocked us tonight. I actually just ran out to Reno to pickup the puller (and hey, maybe I'll win my fortune while I'm here, right?):

IMG_20200215_192135_01.thumb.jpg.c2296386dc99172033e9a85dbb4d1fb4.jpg

IMG_20200215_191604.thumb.jpg.ab61fe2cd5f08caf6c3b64316a98410d.jpg





This is blocking us from getting the front cover off, of course and seeing 100% what happened. So far, NOTHING looks wrong. All of the timing marks are still in the right spots (note: the dark links in the chain will NOT line up after it's been rotated, but where all the marks are on the cams and crank are EXACTLY right - not even off a tooth):

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imagejpeg_0.thumb.jpg.003f473ea1bdabbddee918a4f665a02c.jpg

imagejpeg_2.thumb.jpg.7a463a4bd74c221bf5fadbcaa1531f41.jpg





You can also see the guides are still tight, meaning the tensioners should be fine.


-TJ
 

TJDon

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Interesting. Dropped valve seat maybe?
 

tjZ06

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It’s a Jeep. Anything’s possible
4.7-3.7’s are notorious
They certainly are... but just so weird it did it after all this work. Maybe the HLAs really were getting weak and the valves haven't been really opening 100% for a while... having the valves coming back to the seats from full travel was enough to knock a few seats loose?

-TJ
 

TJDon

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Hard to say. I’ve had customers state all kinds of scenarios when the engine “started to run crappy”
Dead cold start up
At a stoplight
Engine overheated then misfired (dropped seat, bent valves)

I’m also wondering if something accidentally fell down into the cylinder? Was the spark plug electrode flattened out? Like made contact with something?
Once the head gets pulled off, hopefully you’ll find a solid answer
 

tjZ06

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Something dropped into a cylinder was my next though but we covered the spark plug holes as well injector holes and obviously were careful. What are the chances we dropped something in two cylinders side by side and no others? Possible, but not probable...

I need to talk to the reman company Monday and make sure I can pull the heads on the core... but I really want to know what the heck happened...

-TJ