Engine turns halfway and locks up?

Hey guys, I am about to spend some time on my Merc and now the motor is locked up. I rule. Story is I had a plate over the carb hole on the intake, and somehow in the past few months of rain it must have gotten water in it, it's been sitting outside for two years in the chassis with no issues until recently. So, it turns over between 1/4 and half a turn and locks up. Where should I be looking? Am I wasting my time pulling the heads? Most likely the problem around the crank? Any insight would be appreciated.

 

Piston(s) probably hitting rust. Put MMO or simular it & let it saok a bit. work it back n forth & see if it'll break loose after a bit. Pull the plugs?

 

It sounds like you have a cylinder nearly full of water, it's hydrolocked. Pull the plugs and try it again if that dosen't work it's time to pull the heads. It's unlikely the bottom end is causing any problems.

....................Jack

 

Sorry, I forgot to add, I pulled all the plugs figuring hydrolocking was my first route. Nothing. MMOd the death out of it, and nothing changed. Sorry about neglecting that.

 

Flathead? If so, it is probably a stuck valve. They can stick shut and the cam/lifter won't budge 'em.

 

Have you have checked the oil yet? I had issues with water getting in my engine last summer. Come to find out the oil pan was full of water to. I managed to free my engine up by working it forwards and backwards, spent almost a whole day working it back and forth. I've run it for short periods of time, but because of a rad leak, I have yet to run it long term to be sure it is OK. Seems to smoke a little right now, but its only had a minute or so running time per start. The new rad came in yesterday, hopefully I can get it installed and get some running time on the engine. Gene

 

Any chance something like a nut or small bolt fell down the intake and is sitting
on top of a piston?

 

This may sound really crazy but I had a small block that had the same symptoms and when I pulled the heads there was a large mouse nest in one cylinder!

 

Just how cold has it been there if you got water in a cylinder or pan could it be ice.

 

Stuck open valve on a OHV engine could do this.

 

My guess is rust in one or more cylinders. Don't force it, pull the heads and clean up the cylinders and valves.

 

First , can you tell us what engine are we talking about ? That might help us figure something out for you .
I would drain the oil pan and see what comes out . If the engine is turning over some it really sounds like something is in a cylinder that is stopping the piston on the compression stroke .
The best thing to do is pull the engine and remove the heads to see what the problem is . If it's just rust starting in some cylinders , just clean the cylinders up and see what happens . But honestly if the engine is out of the car with the heads off , then you might as well just finish the job and hone the cylinders out and install new rings . Hopefully that will be all it needs . That way you won't be guessing if the rings would still be good or not when you go to start it the first time .
I build engines and it's not that hard to do a re ring at all . It's easy and then you know the engine will be good to go for a long time and not leave you stranded some night .
Just a thought !

Retro Jim

 

That's easy to figure out. You pissed off the Merc gods when you cut up,and scrapped that Merc frame.
That'll teach you.

 

my uncle bought a y block that was like that for 10 bucks...had a dirt dobbers nest in it .

 

Just from sitting, rusty cylinder is most likely. Not much going to freeze the crankshaft itself. You sure it's not in gear???

 

Thanks guys, it's a 51 Merc but the chassis and drivetrain are 1977 Olds 98. So, it's an Olds 350 with some sort of automatic. My wife is sick and still sleeping so I am starting out late, but if I can get this turd shoebox out of my garage and get the Merc in later today I will report back with my geological findings in there. Thanks guys! PS...Jim, the engine is still in the car and I would really rather not pull it. If I were to ideally I would pick up a 455 for it's place, and then remount it 4" back as I had some clearance issues, then cut a driveshaft (which is already installed), redo the trans linkage that's already there....so...it would really be opening a can of worms.

 

OK, since it isn't a flathead, my best guess is that you have a cat stuck in a fan belt.

 

Ha!

 

If the starter/flexplate is still attached, maybe thats stuck inguaged.

 

If you have not turned this engine over since installing the trans and converter, check the length of the converter and flex plate bolts.

 

I had it happen last year on a Corvair engine I bought that had been shelved in Florida for a decade. It turned over about 3/4 and then locked.
I hosed down the cylinders with PB Blaster and let it soak for a while, then slowly kept turning it back and forth, lock-to-lock.
It eventually freed itself.

I'm sure it was surface rust toward the top of the bore, catching the rings.
I could feel it working away as I rotated the engine back and forth.

Engine has been driven daily for the last 5 months, without any blow-by.

-Brad

 

Same deal here - A friend had a '35 Phaeton with a strong running 265 ahead of an early Ford trans. We pulled it apart to do chassis and brakes, and a year later went to start it and... Well, no! Ended up hosing everything down with MM and a day later put it in gear and spent the better part of a day pushing it back and forth. About 3:00 it just kept rolling down the driveway instead of stopping! Fired it up, and drove it to LARS a week later.

 

I remember someone over here having a similar problem, bolts on the timing gear were too long and only allowed the engine to rotate so far.

 

I'd pull the valve covers and check for a stuck open valve.