Causes for a seized engine?

[chuckstp]

An update for anyone who might follow this. Based on the questions and feedback so far, I managed to turn the engine backward and forward through a rotation of just under 360 degrees of the crank shaft. It appears as if all the valves move properly and the ones on cylinders 2 & 3 are up when it stops. I pulled off the sump yesterday and everything looks good from underneath. I confirmed that pistons 2 & 3 are up, but stop shy of TDC in both directions.

It looks like the next step is to remove the head and see if I can find anything there. When I looked at the pictures of the front cover and the timing chain, I didn't see an easy way to account for an obstruction at 360 degrees of rotation. Thanks for the feedback so far, and hopefully I will get a chance to lift the head over the weekend.

[triumphtr7guy]

Sounds like its time for the head to come off, from what you have described, it sounds like you dropped a valve. The rockers will move as you turn the engine, but you would have to look and see if the valve stem is there, and it may have broken during the rapid ignition of fuel source re= the bang! And if the vehicle is as you said been sitting, probably wouldnt hurt to have the head done at this point, save some aggravation down the road with other problems that could crop up. Good luck, Bruce

[chuckstp]

Mystery solved!!! Once I popped the head off, it became fairly clear exactly why it got stuck like it did. At first this posed another mystery of how the lock washer got in there since it was too large to fit in the spark plug port. My neighbor suggested it may have gone in through the carburetor which is fairly likely. My guess is it dropped in when I first took it off to empty the stale gas.

[bugeye88]

How about a pic of the head #2 cylinder. The Piston doesn't look too bad.
Rob
Bugeye88

[westcoastkevin]

Hopefully you have not bent the connecting rod.

[chuckstp]

I'll send a picture of the cylinder sometime later when the sun comes up. Well, depending on the weather. It's raining here now. With my ignorant eyes though everything looks great in the engine. It looks like the washer got sucked into the engine while I was trying to start it so it didn't have a chance to bang around on anything. I suppose to check the connecting rod, besides a visual, I should be able to measure the distance from the block to cylinders 2 & 3 at TDC.

[chuckstp]

As requested, pictures of the cylinder head. First is #2 which looks great along with the slight impression of the washer in the carbon.


The other picture is of #4 which looks like it has some issues. I presume that is the intake valve with the splits in it. Anyone have a guess what would cause something like that?

[yorker]

The other picture is of #4 which looks like it has some issues. I presume that is the intake valve with the splits in it. Anyone have a guess what would cause something like that?

Exhaust valves are always or almost always smaller than intake. "Intake valves are usually larger than exhaust valves because pressure forcing charge into the cylinder is much lower than that forcing the exhaust gases out."


The cracks are kind of odd but somewhat similar to some burned valves I've seen. http://www.aa1car.com/library/ar1192.htm

[bugeye88]

#2 looks OK if the pistons 2 and 3 have the same measurements at the top of TDC. As for #4, Yorker is right is saying this is not good. The burn and cracks on #4 exhaust are not indicative of a healthy environment there in #4. Does not explain why the engine came to an abrupt halt though. There could be some other "surprises" lurking in this engine.

Rob
Bugeye88

[ccbullet]

I'm having similar issues with a 1966 IIa. Long story short, it was sitting for a decade, and now my problem. When I bought it, I thought I only had ignition issues to figure out because the starter was turning over fine. But tonight I was trying to turn the crankcase pulley and it's stuck. Will try to chip away at troubleshooting...any advice would be helpful. Thanks!