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Discussion Starter · #1 ·
Doing LS swap and finally got the motor in and married up to the th400. When trying to connect flex plate to the converter, I noticed I could only rotate the engine so far, about 270 degrees, give or take.
Pulled the pan and can’t see anything there, I took out the bolts connecting converter to felxplate and that didn’t do anything.
Prior to installation I pulled the front timing chain cover and water pump to put in a new oil pump. I can’t for the life of me remember if I turned the motor completely over by hand after doing that but it definitely did before and I thought I rotated it over completely after the oil pump It seems odd that it turns over very smooth until it hits a certain point each time.
2 thoughts, something going on under timing cover after instal of the oil pump. Or second option is something got dropped into an exhaust port or intake port or something and won’t let the motor turn past that point.
really would rather not tear it all apart just searching.
Maybe something anbout being connected to trans now even though Converter and flexplate aren't attached. Converter spins freely.
Any ideas before I dig in?
 

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Discussion Starter · #4 ·
The motor is a stock 5.3 that came out of a running truck so I felt pretty confident that the valvetrain was installed correctly. I was trying to think back to changing the oil pump if that could have changed anything but I can’t think of how that would happen.
I tried to look in spark plug holes and didn’t see anything.
I may need to start pulling it apart as I am scratching my head what could be the problem
 

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Discussion Starter · #19 ·
I used an alignment tool for the oil pump so felt like it should be ok. I will triple check how I set the timing marks but remember clocking them in per the instructions.
 

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Discussion Starter · #21 ·
Good question. I out a piece of tape on the balancer at 12:00 and rotated it until it stopped and it stopped at 9:00. I rotated it back and it stopped at 12:00 again. Very consistent. It only leaves about 90* more rotation left
I agree about the timing. It sees like that would be way to much rotation to be able to happen base upon timing being off. I am going to decouple from transmission first and see if there isn’t something hanging up there, but I don’t think that’s it. After that start pulling it apart and see what clears it. Intake off, timing cover, oil pump etc.
 

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Discussion Starter · #23 ·
Pulled the motor free of the transmission today, still locks up. Pulled oil pan and can’t see anything that is blocking rotating assembly. Pulled the front timing cover ans removed the oil pump, still locks up. Pulled the heads off of it, sure that I was going to find something in a cylinder and nothing there, and still locks up.
I had bolted it back up in the motor mounts to hold it when I pulled heads etc so I am going to pull it out, throw it on the stand and pull the flex plate and flip it over to look closer in the rotating assembly.
I don’t feel like it could be something loose inside the motor as it rotates freely right up until it hits a certain point every time. I keep looking for where I could have out a bolt in the goes through the block or something to hang up a rod or something. Will update as I keep digging.
 

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Discussion Starter · #24 ·
Well finally figured it out and it is not what I was hoping for. The top of cylinder 8 had enough rust that it would not let the cylinder go up. I cleaned it up a little so I could see what I was facing. Doesn’t look good.
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Discussion Starter · #28 ·
I bought it from a “reputable” restoration shop locally and the owner gave me the details on how he got it and that it was a very good running Yukon that was wrecked. But to answer your question, nope, didn’t hear it run. I had talked to the guy a handful of times and he does a lot of swaps into c10’s and some Novas. Kicking myself now for not doing a more thorough inspection. Plan was to throw a new oil pump in it, knock sensors and run it.
I have a call into them now and will hopefully talk to them this week about it. I don’t feel confident that I am going to get a great response as it has been 10 months since I bought it but who knows.
Initially I was hopeful that it could be honed with some level of satisfactory results, not sure that is in the cards.
 

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Discussion Starter · #31 ·
Was told it has around 140k miles. If I had to guess, it may have had 140k (who knows) but it sat for a long time. Only way I can see that happening.
 
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