Trying to finish 5.0 timing job, engine not rotating smoothly

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SailLaser

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Hello all, brand new to the forum.

2011 LR4 with ~140k miles. No timing codes but decided to do the preventative timing chain and guide replacement. All was going well but I’ve hit a snag.

Followed shop manual to a T to reassemble new guides, tensioners, VVTs, and chains. I was pretty sure I timed it correctly. Next came the instruction to check the timing work. Inserted old crank bolt with a washer and started turning. But I hit a couple of stops going through the two rotations. I can’t say it was a metal hitting metal stoppage, but since there is a chain connecting things, it might have made it feel a little cushy. I eventually got it through the two turns by being able to go backwards a few degrees and progressing forward quickly (some stoppages taking many, many tries to get through). At two turns, cam locks did in fact slide back in nicely.

Second guessing myself, I tore everything back apart and reassembled. Removed spark plugs. Started turning, but same situation. Distraught, I bought a borescope, and in fact regained some confidence knowing that at least at the first two stoppages, valves are not hitting pistons.

Is there anything else one can think of that would cause this sort of stoppage? Having ruled out valves hitting pistons, my next idea was bent valves, but there doesn’t appear to be visual damage from the top of the head. Damage to piston heads is more mysterious as I learned yesterday that the pistons have little indentations where the valves are anyway.

Next inquiry is whether the pumps, oil and fuel, driven by the bottom chain could be causing resistance. I found the chain to be quite slack on the static guide side, but the tension guide still had some travel in the spring. I know there is allegedly a timing mark on that chain, but don’t see how a specific timing offset could cause any problems with gears that just turn pumps.

Any help or ideas are greatly appreciated. Thanks so much.
 
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powershift

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I'd re-assemble and fire it up if you haven't already. There is going to be resistance rotating the cams against the valve springs. There are a lot of springs one for each valve so that is 32? If you had the heads off and it was like that then that would be sus.
 

Rover Range

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Another tech at work here had the same issue.
Pulled everything down and retimed the engine.
Eventually, said f it.
Fired up and ran great.
 

LR4 2011

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I thought my engine locked up also but I determined the valves, cams and springs were dry. I used a paint brush and brushed the cams down with clean engine oil and the rotation became smooth again.
The engine is tight like mentioned above, so keep a smooth turning motion going when rotating on and off of the multiple cam lobes.
 

SailLaser

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Following up to thank you all and in case this thread might help anyone else stumbling through the dark as well.

I solved the mystery a little while ago but life has been getting in the way of putting everything back together and actually making sure everything functioned.

The stoppage was...."Gunk". Not valves, not fuel pumps, and I wasn't going crazy...
For the affected cylinders, it was restricted at the top of the cylinder which meant that I couldn't get a clear view of what was happening with the borescope. I took a third look, this time carefully rotating the crank while the camera was inside each cylinder, allowing the camera to travel up with the piston. Attached pictures are what I found. It's what I would estimate to be about 1/2 - 3/4 of a centimeter of slightly rust colored but mushy chips of "gunk" stuck to the flat part of the cylinder head between the two exhaust valves (red circle in one of the images). Some weird amalgamation of what I would assume to be carbon, oxidized metal, and other foreign materials. I really can't say where it came from, it may have even been there to begin with and been knocked into an obstructive position.

It shares a very similar color and consistency to the residue left in the injection ports and seats. The weird thing is that when I started taking out injectors and the valve cover off of one bank, I realized upon visual and tactile inspection of the injector ports that I definitely should have vacuumed or blown with compressed air around the cover and injector seats, as there was much debris on the seats and making it's way further down. And when stripping the other bank, I did exactly that. In fact, both vacuuming and blowing compressed air. The seats and ports were much cleaner upon removal of the injectors and valve cover this time. And yet, there were ~4 cylinders, 2 in each bank, that had this debris stuck to the head, barring the piston from reaching the top of the cylinder.

I spent a couple hours knocking it loose to fall onto the piston face then vacuuming very thoroughly until the piston faces and cylinder walls were flake free and the head where the buildup was was as good as it could get. I did this in each cylinder that created a full stoppage (~4 cylinders, 2 in each bank) and ones that were just causing a slight bump but could push through (2 cylinders). Other 2 were completely fine for some reason.

Engine turned over by hand completely smoothly after that. Finished putting the truck together today and started right up. So glad to have her back. Perseverance is key as mentioned frequently in other threads.

Thanks again to everyone for helping and replying, in this and the many other timing chain threads.
 

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powershift

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Corrosion probably dropped down on top of the pistons and fell between the piston and cylinder wall and on top of the rings while cleaning it. I would have left it or removed the heads and cleaned the corrosion off on a bench because now there is potential for premature ring seal failure later on in life.
 

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