If you can turn your crank back and forth about 1/4 inch either way usually means the crank is free but the pistons are seized in the block. The engine will definately have to be taken apart. Engines are funny people. One day they love you and the next day they leave you.

HOLD UP!! Don't get too anzy and start taking everything apart. Using a large socket and torque wrench try rotating the engine the opposite direction!! This can un lock the probable cause which could be a timing chain that broke in at obe of the pinned connectors causing the chain to wrap around and JAM the engine. Start out by removing the timing chain cover instead. This is why i am telling you to turn the engine in the opposite direction, because this would reverse the condition that caused the lockup.

Another thing to look for..Take a large screwdriver and underneath the truck turn the flywheel by turing one tooth at a time. Many times vehicles without dust covers can get an iten stuck in the flywheel area. But anytime an engine runs okay without knocks or clanks and locks..generally it will be something more external such as timing chain wrap around from a PIN coming loose in the chain assembly.

If the timing chain broke or jumped a bunch of teeth, the pistons may have hit the valves - Ugh - unless the 360 is a free turning engine.

I don't have information about your engine. If it has a distributor, remove the cap and rock the crank back and forth. The rotor should move, maybe with some play. If the rotor does not move, this is a clue.

If your engine does not have a distributor, remove a valve cover and rock the crank back and forth. Do any of the rocker arms move?

Let us know what your find. You've got us curious.

If he takes a valve cover off of the engine, he needs to observe as to whether one of the retainers came loose from a valve top and dropped a valve in a cylinder, causing a totally loose rocker arm as well.

As far as checking for movement of the distributer shaft under the cap, that is wasted time simply because it won't move if the crank assembly is "LOCKED", nor would that relate to the issue at hand of assembly lockup.

And if a timing chain breaks or skips that CAN NOT MAKE A PISTON TOP TOUCH A VALVE,...because crank and rod assembly does not change it's stroke height because of timing or chains or cams, as it is a pre assembled fixed rotating assembly. The only way a piston can protude in bore assembly height is to disengage from crankshaft at insert and bearing cap.

Ok guys. Thanks for the replies. I haven't had time to do anything to figure out the problems. I am going to hit a few tries as rotate the crank with a large socket to see if it might be the chain that broke or a dropped valve. Take the plugs out to reduce some pressure. The valve covers first because they are the easiest to do. That is if the engine does turn with breaker bar. I might have to make a custom socket with arms on it to catch on couple of the pully bolts to keep from loosening the balancer bolt as I try to free it backwards. I will get back to you all in a few hrs. Thanks for the replies all.

Not looking good here. I have to pre fab a socket with arms to catch a few pully bolts now. If it doesn't turn then I would have to say a piston seized in the block. But it doesn't make sense though. 30mph and it stalls then I start it again and pull off road and it stalls and locks up.But I have to wait till tomorro to fab my socket. I could pull the balancer and put a rag around the crank and then use a pipe wrench on it. I don't have a special socket with groove for key way. I think I will just pull the balancer and use pipe wrench. It would be stronger and I could use a pipe for an extender and try to free that puppy up. See what gives.

Before you go and remove your balancer, have you tries removing your dust cover and prying with a screw driver at the edge of the bell housing and flywheel teeth??

And yes, taking the valve covers off is a time saver because if you dropped a valve you are going to have a rocker arm with 2 inches of play for sure.

For an egine to run smoothly without a metalic noice is strange, but could be a valve dropped and inserted at a cylinder angle and locked everything.

Let's ease up a bit. Remove the spark plugs to make the engine easier to turn (under normal circumstances). Apply a socket and handle to the damper/pulley nut and try rocking the crank. Under normal circumstances, the crank is fairly easy to turn and can be turned either way without loosening the pulley nut. If you have to apply very much force, its jammed and forcing it will do no good.

There is one more item to check - the starter. It is rare and happened on cars made from 1930 through 1953. I haven't heard of jammed starters in recent times. The starter can engage the flywheel, then go bad and jam. This locks the engine until the starter is removed. On old cars, sometimes we could unlock a starter by turning the engine backwards. (It seemed to happen on Saturday night dates.) This only works with a manual transmission. Have an assitant sit in the driver's seat, put the engine in a forward gear either second or high, then while the assistant holds the clutch in, the second person begins to rock the car or roll it backwards. The assistant lets the clutch out as the car moves backward. This will bump the engine backwards (without any tools). Often, this technique would release a jammed starter.

Unfortunately, I have little hope that it is a jammed starter. I see in a later post you stated that the engine stopped while going 30 mph, and was restarted and the engine quit again.

Whatever you do, do not remove the damper/pulley and apply a pipe wrench to the end of the crank. This is a press fit surface and is precision machined to a tolerance less than .001 inch. Yeh, the pulley/damper is hard to get off the crank. It is keyed and pressed on. You'll need a puller to get it off, and will likely have to remove the radiator to get access and to prevent dings in the radiator. Let's reserve taking off the pulley until later. You only need to remove it if you are removing the timing chain cover. If you can not rotate the crank using nomimal force with the spark plugs removed, there is a serious jam inside and forcing it will do more damage.

As always test don't guess. An engine could be locked up simply because of an internal failure. But it really doesn't happen just out of the blue. There are always signs, it comes down to the driver noticing them. When one of these engines appear to lock up suddenly, it could actually be a transmission problem, or something as simple as the alternator. To find out, you'll have to first remove the belt and now see if the engine turns. Attempt to unbolt the flywheel from the torque converter (assuming this is an automatic, I didn't see where this was specified). Unbolting the flywheel can be quite difficult if the crankshaft in the engine wont turn. This only has a 7/16" front crank bolt, so be careful about how much torque you attempt to use to turn the crank by hand. If this isn't turning at 50-70 ft/lbs something is causing it to not turn. Its quite likely you may need to drop the pan, and pull main and rod bearing caps one at a time to see if you can then get the crankshaft to turn. You might even need to do this in order to unbolt the flywheel from the converter. Do not attempt to turn the crank with a pipe wrench with the damper removed. That would at the least be a waste of time, you can turn the engine with just the regular crank bolt, again watch how much torque you apply. At the worst, you could do more damage to the crankshaft, and/or the pulley key-way. Forcing the engine to turn now will not allow you to run it again without a repair, so don't damage anything else trying.

you have spun rod bearings and broke rods before? whew, you must be hard on motors. or maybe you tow a lot or maybe you don't maintain your vehicles? don't want to get you mad but very few people blow motors. yes some do fail out of the blue but its not common. they do sell crank adapters to turn over motors. gotta take of the balancer to fit it on though. a 96 chevy 350 is pretty cheap used. not hard to find one.

Take the serpentine belt off and try to see if it spins. You may have an alternator locked up.

not to be rude but there is no way in hell you have an
alternator lock up. Water pump lock up, power steering pump
lock up, or A.C. compressor lock up or all of the above at the same time. That will never stop and engine from running. It will burn the belt off first. My money is on Joe MN. You've spun a rod bearing. Bottom line. Why try to get it to turn. The motor is done. It has to come apart and be rebuilt or replaced.

One thing i forgot and no offence but i don't think Earl53
has much experiance in engine failures. You have no idea how many engines i've seen when the piston kisses a valve.
I can't count how many push rods i've bent on my 312 on an
over rev when the piston kissed a valve. not that common on
hydrolic lifters but normal on solid lifters. They call it
an interference engine. Timing belts are non interference
engines because the belt will break or jump as you drive.
Normal. Ever seen a hydrolic lifter " pump up " and punch a valve through the piston top ? Almost normal on the old
318 dodge. 390 had the same problem. When a rod bearing spins the connecting rod will also push the piston up higher than deck hight but if the valve timing is ok there will be no valve kiss. ( almost no valve kiss )if operated
at normal road speed. Please disregaurd this post if found
offensive.

a broken valve with piston bits in 1 cyl could make the motor turn over not well at all. could you pull some plugs and look for debris on the plug tips? maybe no oil pressure seized some bearings. crank, rod, or cam bearing?

kalinin.

An alternator can lock up and cause a no-start, no-crank, can't turn the crankshaft by hand on these! The 4.3l V-6's are known to do it as well. A good belt, with a good tensioner really grabs the pulley firmly.

I might partially agree with that. Usually a bearing seizes
as it stops moving and will not turn again on the next start. Funny thing you mentioned a 4.3. My brother had one
in his shop last month. Alt seized but didn't stop the motor. The belt caught fire and seriously damaged the under hood and related parts.They wrote the car off.

The reason I mentioned the alternator possibly being locked up is because that is what happened to me on my 1990 Silverado with a 350. The engine just stopped dead at a stop light. The starter would not turn the engine over at all, only engage and stop. I normally would not have thought that the alternator would prevent the engine from turning, until it happened to me. Sometimes we get lucky and it is the simple things we overlook.

LOL..I suspected this topic was made by someone, then either site administrators followed it up to make it appear somewhat real to the NOVICE or maybe a group of people "bored wanna be guys whom know one another" decided to play on a forum.

Other than my own replies..the replies are NONSENSE and FICTICIOUS. You sillies that are arguing and "catching and throwing" do not even know if the distributor is on the front or back of the 350.

As i said before..you clowns do not know who you're responding to with your nonsense.

Earl.

Fill out your member page so we get to know who you are, and see what your experience is. To get to my page simply click on the link next to my name. Now granted mine does need updated, I think its been four or five years since that one was written. But as an ASE CMAT, L1, A9 with over 32 years experience as a full time technician, who averages fifty cars a week inside my own shop, who owns fourteen FACTORY level, or otherwise known as O.E. scan tools, attends over 100 hours classroom training each year, and as an instructor, delivers approx 400 hours of continuing education classes for professional technicians all over the eastern United States I'm pretty sure that I don't have to tolerate statements like the ones you have made in this forum.

In your own words, "You don't know who you are talking to", but now you should have an idea. If those (my) VERIFIABLE credentials aren't enough, I'll get a few people from around the country to chime in.

Come on, Earl53, Lighten up. You have been attacking some of the best responders on this forum. It makes me wonder why?

My 91 350 truck lucked up .it was hydro lock from a stuck injector. Pull serpentine belt and spark plugs .then try to turn crank. Easy to try.

I have a 2003 Chevy Blazer 5 speed, about three weeks ago, after driving it all day, I went out to move it and the starter was slowly getting weaker and weaker then it stopped. Turned the key and nothing at all. No clicking sound (I've replaced a starter on a Chevy S10 before). Finally was able to get the starter out - one of the cables broke off (rusted through). Tried to take a socket and wrench to move the flywheel. I can only turn it counter clockwise. Haven't tried to roll start it since I took off the starter today. Any thoughts???

Okay fellows, my step son was driving my 2001 ford sport track, he stopped turned it off and would not start again, no warning no noise at all, oil pressure has been good, I replaced the starter after checking it being bad, the battery is showing 13 volts and with a jump the engine will not turn over, I tried to turn it by the crank shaft pulley bolt and will not move, and the other direction it just spins off the bolt.

Is it possible that a valve dropped just the right moment when the engine shut down as the piston was moving up ?

Can someone help me I got a chevy and I put some new head gaskets on and I crunk it up and ran good so I cut it off put water in it and then my starter was smoking so then I got a new starter and then I try ed to crank it and it seem liked it was locked up it'll turn a little bit when cranking it over but I try ed to turn crank shafts with breaker bar it hard to turn won't turn don't know what to do can someone help me please.

Hey My Gmc Yukon truck 2001 it's been down since April of this year. That I driving my GMC Yukon truck it was running good. The next morning when I went to gmc Yukon and crank it up it's was fine til I put it in drive got up the road the same day all suddenly my Gmc Yukon truck steer wheel had got hard then shut my truck off completely..Now my engine is locked up tried pulling on the belt to c will it turn nothing. When under my truck used a screwdriver to try to move one the teeth on the flywheel nothing won't turn at all.. Need help what must I do bout get my motor turn back over so I can crank it up again.... Replace everything on my truck but my motor will not turn at all.... I used a puller to put on the crank bolt it hard it will not turn it all... Help plz give me advice.. Didn't hear no knocking noise from engine cuz my engine is a1 what cuz it to lock up

Yes my 2001 Montero Locked Up out of the blue while idling. No oil light whatsoever. I just notice it suddenly lost power as I was about to park it. Then engine died in a way like it locked. Tried cheater bar to turn engine no luck. Recently though I charged the battery full and it budge a bit so I turned again with a cheater turning opposite direction and it did. It turn about half way. There is hope the engine can be fix while on the vehicle. Maybe bad camshaft or broken valve spring which bent the vavle. Worn rod earing would have thrown oil light or any bearing that is worn. I may add too that I recently rebuilt the head myself so there is a posibilty I may have Installed the valve train rod backwards which would cause the oil hole not to line up causing oil starvation on the cam shaft, I did notice loud valve noise when starting the engine that diminish once it start but gets loud when raising rpm. I also want to mention it also had broke valve spring on piston 1 but I fixed it amd ran like a champ before it locked up in me.

I have a 2000 Chevy Silverado 5.3 I can spend the engine counterclockwise all day long but go to spinning clockwise and it has a hard spot and will not move engine is not locked up what could cause this

I have the same problem with my 2000 4.3 chevy. My question is, is it possible that the motor locking up can happen multiple times because that has happened to me. I had a coolent going into the oil problem, wrongly diagnosed it as a head gasket issue when in the end it was a lower manifold gasket proble. The 1st time the motor locked up I was doing 30 mph and it shut down. Was able to start it again and move it out of the road. The next morning I went to pick it up and it started and ran about 200 yards and locked up again. I then towed it, did the lower intake manifold fix. It fixed it and ran ok in the driveway, took it for a test drive and it locked up again after 10 minutes. Any answers from anyone?

It has piston hole full of gas it will lock up fuel regulator