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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: thirsty on March 12, 2012, 12:59:34 pm
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Well the time came to start my truck this past weekend. It didn't go so well. I have a problem with something only letting my motor rotate about 270 degrees at the crank.
Here is the history on the motor. I bought a C10 with a blown transmission just to get the cab. I drove the truck home with it dumping tranny fluid. The motor ended up in the truck I bought out of necessity. It was a spare race motor for a local race team. It is a post 86 non vortech with low miles. My build changed directions and I ended up dropping that motor in. I know it ran well because I was the last person to drive it. It has been sitting for 3 years now. The only bad thing that has happened to it was that it was in my truck during my failed body job that never got done. It sat outside in my chassis for 9 months. Other than that it has been in the heated garage since it was pulled from the donor. Currently it is in front of a SM465.
When we tried to start it I was more worried about the starter or the carburetor from sitting. So I got everything set and hooked a booster pack to it and bumped it over. It started to turn then stopped and wouldn't go any further. At the time it sounded like the booster didn't have enough charge to do it so I swapped it out for another and it did the same thing. Then I realized what was happening and turned it by hand only to find that it turns perfectly until a certain spot in either direction. Pulled the plugs everything seemed normal but it is hard to see in there. Pulled the valve covers, everything seems to be normal there. Pulled the starter, flywheel cover, and fork boot but didn't see anything there either. Had someone depress the clutch pedal and it still stops at the same spot. It almost feels like there is a wrench stuck somewhere binding it up.
The distributor has not been removed since it was driven last either. My next plan is to try and get a scope and look around with that. Then pull it out and try it just to rule out the clutch and tranny. Then I will open it up if I have to.
I'm having a hard time believing that it just broke a rod or something. It was never raced but put in the truck when built motors where no longer legal to race and ran for a few years during the summer with no problems.
Anybody got any ideas what it could be? I would really like to find something stupid but it's not looking that way as of now.
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Big dent in the oil pan or something fell down into the intake?
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Big dent in the oil pan or something fell down into the intake?
:'( Remove all the spark plugs and turn it over by hand until it stops, then peer into the cylinders to see which piston pair is up and check out those two cylinders first. It has got to be aggrevating after all the care you've taken! >:(
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I've had rust on the cylinder walls stop a motor from turning over. It wasn't horrible, but enough to stop it. I hosed the cylinders down with Marvel Mystery oil, made a sacrificial crank pulley with holes in it for a bar. Then just kept working it back and forth until I could turn it 360. Then I fired it up.
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Big dent in the oil pan or something fell down into the intake?
I never had the carburetor off it either. It's funny you mention the oil pan because I did think of that and checked. Not that I wanted to see a dented oil pan either but that's what it acts like.
:'( Remove all the spark plugs and turn it over by hand until it stops, then peer into the cylinders to see which piston pair is up and check out those two cylinders first.
That's what I was thinking and also why I mentioned the approximate degrees the crank turns. I have a feeling that I am going to find rust where the pistons sat. If it was just from humidity I would think that it would not be bound in that spot. More than likely it has a lot to do with the mud flap that was thrown on top of my engine to protect it after they took my front clip off and let it sit outside.
This is how I found my truck sitting one state away when I went to check on it during the body work that never got done.
(http://www.suitorsgarage.com/jsuitor/truckoutside.jpg)
Then I got it back but couldn't bring it in the shop so I covered the engine and it had to sit like this until spring.
(http://www.suitorsgarage.com/jsuitor/snowedin2.jpg)
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I've freed up stuck motors before but never had one that would move then stop like this one.
Blazin did yours move or was is stuck right where it sat?
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Hate to say my guess is rust in the upper part of one or two cylinders, once i delivered a small block without an intake an intake bolt got dropped down the lifter galley and fill right in one of crankshaft counter weight drilled holes and the engine turn than lock solid in ether direction
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Thirsty I hate to say it, but I do not know if I would be trying to force it to turn over. I would be more cautious and take the heads off so I can see what was going on. Especially since you said you have checked the most obvious problems.
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I haven't been forcing it to turn over. Just trying it when I look into a possibility. When it gets to the bound part I stop there. I have access to a scope but wouldn't you know it is being repaired by snap-on at the moment. If money was not an issue it would already be pulled and torn down. I'm trying hard to be patient and wait for the scope and not guess and start pulling it apart. I really am leaning towards rust in one of the cylinders. If that is the case I am hoping for honing the cylinder and new rings on the piston. If it is worse then it will get the old 73 2 bolt that was in it before just to make it move. That motor had head issues but was strong back in it's day. Then I will have to decide on what engine to rebuild. My choices would be the post 86 that's in it now, the 73 2 bolt that it had before, a 77 4 bolt that is in nice condition and never been rebuilt, or a 400 4 bolt that is still original with even the 2 barrel still bolted to it.
For now the cylinders are soaking in mystery oil just in case. The scope was supposed to be delivered back to my buddy's shop yesterday but never showed. As soon as he gets it back we will use it on my motor and hopefully it will tell us something, good or bad. It is killing me not knowing though.
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Mine would turn about half way around. It took 4 days to get it completely free. Every day I would work it several times during the day when ever I thought of it. After the second day it would turn farther and farther. Third day was about 3/4 to 7/8 around, then the last day it turned 360.
Dropped it in the truck, and ran it for 2 years before selling the truck. The guy I sold it to ran it for 3 years with that motor in it.
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It does sound like possible rust in the cylinders. I would be reluctant try to break it free because it could damage the cylinder walls, not mention possibly break a piston ring and then a teardown would be necessary. Also just a thought: make sure every cylinder is free of water or coolant. I doubt that is the problem but def worth checking.
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I found the issue to be rust in #7 cylinder. I wasn't horrible but enough to stop the piston. It was soaking in mystery oil for 5 days. I also used compressed air to move the mystery oil all around the cylinders. I never forced the crank to turn, just would move it until it stopped. Then I noticed that the marks that I made on my crank pulley were going just a bit further. I've unstuck motors before with success and knew that patience is the your only chance. I was doing the same thing Blazin did just without the sacrificial balancer. Finally during the morning/evening ritual of oiling it and moving the crank it just went around. Even soaked it some more hoping for the best with the rings too. I haven't done a compression check yet either. I was just glad to find out what it was.
Looking back if I would have really leaned on the ratchet (not that I would if I could do it again) I would have noticed it starting to move and known what it was right away. I was being careful trying not to do anymore damage to whatever it was. I have never seen one that would turn that far then stop. Any other stuck motor we have dealt with has been stuck right where it was.
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So if you do a compression check I would be interested in seeing the results. If you do please post, just curious.