Any guess what happened to my beetle engine?
 

Rebuilt the engine this spring, here is the link: http://forums.pelicanparts.com/off-topic-discussions/542626-72-vw-beetle-engine-rebuild.html and my daughter has been driving it all summer, its been running great, no problems. She calls me last night and is pulled off the road, she said it revved up real fast and the gas peddle was to the floor and it would not stop. Got to the car and the return spring on the carb broke so it was wide open. I don't know how quick she shut it down but I don't think it was fast enough because when I drove it home it didn't sound that bad just a loud popping like an exhaust leak and a bad miss. All the valve springs are fine (quick check) but now it does not turn over by hand, something is hitting inside? Will pull it today and crack it open. What do you think? broken rod maybe? no oil leaks so nothing went through the case at least! Will post pics tonight! So what do you think I will find inside?

I'm guessing it's in the heads, a broken valve perhaps that is stuck into the piston now.

I too think it's highly likely a valve. Bent or broken and preventing complete rotation.

Can it be rotated back and forth or is it seized?

Bent valves. Said the voice of experience.

A valve seat may have worked loose.

based on my experience I'd say you will find a valve, upside down that has peened itself onto the wrist pin of the piston.

After going back to your rebuild thread and looking at the pictures of the heads... My vote is a dropped valve seat. They didn't look good even then.
I just aquired a 1969 Bug a couple of weeks ago that I am going to go through. Its been a long time since I did one of those too. Going to be fun!
Fifteen years under a tarp outside, add a little gas, give it a battery, and it runs. :)
http://forums.pelicanparts.com/uploa...1286639292.jpg

+1 for dropped valve seat. Check for a bent valve or two as well.

xlnt opportunity to hot rod the motor

This was my first set of VW heads that I did but I do pretty good head jobs, at least on Porsche heads. I don't think its a valve, not much time today but pulled the rockers and no bent pushrods and all the valves do work when tapped on. The crank only moves about 5 degrees each way then hits a very solid stop. I think a rod snapped right at the crank! as far as the popping noise that could have been one head leaking at the cylinder seal after it over revved, I had this happen before and it sounds just like it. Should have it all apart tomorrow to see... Really nothing much in the oil screen either, had one little metal flake and nothing around the screen...:confused:

Hmmm... Keyway come lose? Scratch that... I have no clue at this point.

I know I will have the answer tomorrow but its kind of fun to try and figure it out now! Just pulled the plugs and even with the little bit I can rock the crank with a wire down the hole each piston is moving so the rods are still all there! Hmmmm There is not a lot to these engines, well start unhooking everything underneath....

OK, before you see what really did happen, I want to toss out my guess. Valves are in place and move, so no valve head has popped off. I'm going to say a rod nut is off and jamming the crank.

And, I'm going to say that a valve did hit a piston. Let me know. :)

No fair. You can't change your guess, Milt.

I didn't change anything. (a) rod nut is off and (b) the intake valve is bent, but it didn't break. That to me, explains the symptoms and why it froze after being shut down.

I'm sure that's not exactly what has happened. If it is, I can fix the motor over the Internet. :D

Maybe I should just order this rebuild kit, 3k gets it all!

http://cbperformance.com/catalogimages/1186.jpg

I am going to take a wild guess,and say that it knocked the skirt right off the bottom of one of the pistons , and it is now lodged down in the counterweights.

My guess
 

I bet you spun a bearing when it overreved. Was loose enough when hot, but siezed whenit cooled down.

bent pushrod?

Is that a Scat kit? I don't have much use for them. Those valve covers are garbage BTW. That type of deep sump sucks....straight cut gears are noisy...

This is for your daughter right?
Stick to no bigger than a 78mm X90.5 and say a engle W-110 cam for longevity and drive-ability. Do some research before you jump in.

Also tear into your old engine first to see what the issue is.