Crankshaft won't turn over completely for TDC

This is my first build, FYI I'm trying to install a new distributor on a 283 SBC in my 50 Chevy, and am trying to get it to top dead center. For some reason, I can only rotate the crankshaft about 270 degrees. I can only get the alignment notch on the harmonic balancer about 45 degrees away from the timing tab on each side of its' center....and then nothing, it's like it locks up. The engine is currently attached to the trans, and is sitting in the car. I had a similar problem when I was swapping out the trans that was originally on it, while taking off the torque convertor. I don't even remember how I got it to let go so I could get to all of the bolts back there, but somehow I did...now I can't repeat it on the front end. I loosened, then straight up removed the spark plugs to allow all the compressed air to escape....to no avail. My neighbor is the one who gave me the engine, and he said the engine performed fine when he swapped it out for a 350. I have no reason not to trust him, and he was as perplexed as I was that it will rotate freely except for that 90 degrees of rotation. Here's an image (not my engine) illustrating what's going on.

 

There is probably something in a cylinder.....

 

Pull the valve covers and make sure all the valves are doing the hokey pokey. You can bop the valve tops with a plastic hammer to be sure they're free.

Remove all plugs so you can turn it faster by hand. Do you hear a clunk at contact? If so there's your clue. If not you may have a rusty bore and when the rings hit rust it stops.

Good luck

 

(EDIT -- I was slow to hit send -- what they said)
Is it possible any liquids seeped into the chamber? Water, oil, and gasoline could put you into hydro-lock. But if you pulled all of the plugs out that shouln't be an issue.

Is it possible a valve is sticking open? Could be rust or sludge holding it open so it interferes with the piston. For the price of a set of head gaskets and manifold gaskets you could find out for sure.

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Maybe something fell in a cylinder, maybe something fell in the intake holding a valve open? just some ideas

 

Sounds like it has been covered very well.

 

You either have a bent or stuck valve hitting a piston or a foreign object is sitting on top of a piston, stopping it from rising all the way.

 

I would be looking real hard at the torque converter/flywheel bolts

 

I'd bet it's a bolt sticking out too far somewhere....flywheel, TC maybe?

 

check your torque converter bolts

 

Torque converter bolt hanging up(***uming the engine was running prior).

 

my guess as well

 

My vote is on an intake valve stuck open. Like Shifty sez, give it a bop.

 

by my crude calculations , with it stopping at 45 degrees before TDC the piston would be 3/4" from the top of the bore. i can't imagine a hung up valve hitting the top of the piston

must be something big inside the cylinder

 

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I'll try the rubber mallet trick and see what happens. I removed all of the plugs, and it doesn't turn any easier...still have to put some oomph behind it. I can't use a torque wrench on it because there's no bolt at the center of the crankshaft. I've been manhandling it....now I've got sore palms! doh.

No clunk on contact that I can detect...it feels like a hard stop, but not solid like metal hitting metal.

I found two of the plugs on the driver's side had some moisture on them, all others were dry.

bolt /nut/ fastener somewhere it doesn't belong

-I haven't messed with any of the inner workings of the engine, only replaced the valve cover/intake gaskets (problem existed before that...just didn't register as I'm a noob).

bolt in a cylinder

No metal on metal feeling when it stops, was able to get 360 degrees of rotation when installing the new flexplate/torque convertor/trans through some dumb luck that I can't replicate.

loose con rod bolt hitting side of block

wrong bolt in flywheel/ converter flex plate

New one was exact replacement, matched it all up prior to installation...used same bolts.

How are you turning the engine? Does it have a bolt on front of crankshaft?

Don't I wish....I've just been manhandling it...and getting sore hands

Remove the plugs to ease the situation

Removed, no improvement.

I don't remember---on those can you remove the converter bolts with engine/ trans mated? If you can get the converter loose and "back" a fraction, you should be able to free wheel it, and eliminate something "to the rear" as a problem

You can indeed do that. But my subsequent same problem at the beginning, then with the new trans installation, and then through dumb luck getting it to rotate freely...I would think that would negate the problem from the flexplate back. It's definitely got some resistance when I turn it, if there's no force applied it doesn't keep turning.

I'll try the rubber mallet option from above....and see what I can come up with. One thing of note, while I didn't notice any corrosion of any type in the motor when I had the valve covers/intake/oil pan off...I did have a decent amount of water drain out when I drained the oil pan. Everything in the engine still had oil on it...no visible rust...but perhaps something occurred inside one of the cylinders?

 

Regarding the torque convertor bolt hanging up, when I mated the trans to the motor, I had the problem of it not wanting to rotate that 90 degrees...same as now...but somehow, I did something and was able to get it to do 360 and can't figure out what the hell I did.....now that its all bolted up and in the car....I'm having the same problem as before, but this time it's on the other end, rotating the crankshaft from the front.

 

It looks like everything has been covered.. To save your palms... Take a piece of 1/8 inch plate / flat stock.. whatever.. Drop a lower pully onto it somewhere around center.. Mark the 3 bolt holes and drill them... drop a 1 inch nut in the center... weld it to the plate.. (weld the inside of the nut) .. Bolt it to the balancer..**** A center bolt.. Best part is... It turns both ways without backing off...

 

***uming the problem is with cylinder #1, yes, but there are 7 others. #2 would be close to TDC when #1 is about 1/2 way up, or so.

 

Manual transmission FLYWHEEL bolts used on an automatic trans FLEXPLATE would be my guess. Does your neighbors ride have a stick shift?

Do you have a front pulley on it yet? Maybe one pulley bolt too long and hitting the front of the block and/or timing cover? Where the motor is untampered with I kinda doubt its internal, unless something went down the intake like others have suggested.

 

I'd be taking the three bolts out of the converter and slipping it back enough to clear the flexplate. It should go back about half an inch without any trouble and then you can see if the crank will turn 360 degrees or it still stops. From your photo and the marks I would say that you have a foreign object on top of one of the pistons. When engines get pulled and stuff gets moved around or they sit for a long time they can tend to eat things that aren't good for them such as bolts, screws and wing nuts.

I didn't think about the wrong flywheel/flex plate bolt thing that 42 hotrod mentioned but you might be able to see or eliminate that by looking up between the crank and seeing if you have one longer then the others that is hitting something.

 

See? Rewards come for trying to help people....I p***ed 400 posts on that last post and am now a member instead of a grenade inspector... Karma I tell ya

Scot

 

Turn the car upside down and shake it and see if anything falls out the intake!!

(Just kidding, hope you figure it out without pulling a head!

 

sounds like rust in the cylinder above one of the pistons maybe try some marvel mystery oil in the cylinders and the fixture someone suggested to turn the crank.you wouldn't be able to turn it by hand to get past the rust

 

Item of note.....I found wet spark plugs on cylinders 3 and 5....and #1 was su****ious.

Nah, the 283 was originally in a 65 Impala with a Powerglide, automatic. Flexplate was from an identical 283...matches in every way...tooth count, measurement, etc.

The front pulley is indeed on the motor, and is the original one. Again, the thing that gets me is that I was able to, somehow, get it to do 360 after I got the new trans mounted. When the old trans was on it, it locked, now that I got the new one on and it's been ***embled for several weeks, I'm experiencing the same thing, but now from the front.

Good idea on the making of a front nut.....1st thing when the rain stops is checking the cylinders, but I'm still confused as to how I was able to get it to turn 360 after I got the new trans on....I was able to turn the torque converter and the flexplate together, it wasn't easy, but I could do it.


Either way, TONS of good ideas, I'll investigate as many as possible in the next few days....providing the rain stops.....and report back!

 

Good luck man. I hope it turns out to be something simple and cheap.

 

Take the torque converter bolts out and back it up into the trans., check to see if you get 360. You can turn the flywheel with a big screwdriver or pry bar, might be slow, but you can. Sounds like too long of a converter bolt, but if not check the valves, or rust in a cylinder, also have all the belts off the engine. It's just a process of elimiation. Keep your cool and just try one at a time and you will find it.

 

You say you had a "decent amount" of water in the oil pan. You shouldn't have ANY.

Did the water in this motor freeze recently? If so, it may have cracked a cylinder wall and the wall got pushed into the cylinder. It will break right above the top of the piston. The piston is hitting it and will not go all the way up. The excess water went past the rings and into the pan.

I have personally seen this happen to a buddy's motor.

I hope this is not the case for you. Best wishes.

 

check flywheel bolts, then valves before taking off the heads and finding something died in there

 

So you never heard it run? How long has it been sitting around? Inside? Outside? Does your neighbor have kids?

Hmmmm......

 

Converter not fully seated in front pump and binding?