Fintail 4cyl - stuck - remove timing chain?

[kelf]

Hi all,

I'm working on getting the head off of a 1966 M121 4 cylinder. (I was fibbing a little - it's actually in a 319 bus; see pix at http://www.geocities.com/mb319camper .)

The engine is frozen, and I can't rotate it around to move the timing chain. I released the chain tensioner, and removed the cam sprocket, and there's lots of slack in the chain now. But there's a little guide that keeps the chain engaged with the crank sprocket, so I can't pull it around - and I'm afraid the master link must be in the inaccessible area between the crank sprocket and the tensioner sprocket.

On the other hand, there's a little guide in the head that the chain is looped around - so the chain won't let the head come off unless it's undone. And I can't see how to remove that guide, either.

Hacksawing the chain seems unforgiveably crude (and is it hardened anyway?) - but does anybody have an idea how I can disengage it to remove the head?

Thanks...

Kelly

[Ridge]

Kelf,

Don't know about your particular model engine but on the 123 Series MBZs, if you want to get the cahin off, you just stuff some cloth down the chain gallery so no bits get into that area and grind off a couple of the heads on one link, push the link out and there you are. Chain now open and you can proceed with the head removal. You'll almost certainly want to put a new chain on when you rebuild, so don't worry about finding " link". Besides, there usually isn't one as you just crimp the loose link on installing a new chain. Good luck on what you find.

Ben

[Mark DiSilvestro]

The guide in the head should be held by pins, pressed into the front of the head. These pins have a 6MM thread for use wth a puller, or you can make a puller using 6MM bolts, nuts, washers, spacers, sockets etc.
Hope this helps.

Happy Motoring, Mark

[cth350]

Wait, you either want to take the head off or you don't. The head comes off nicely with the chain still in place. Just pull the gear off the cam with a puller.

The best way to unstick the motor is Kroil. The next best way is a 50:50 mixture of Marvel mystery oil and kerosene. Pour some into each cylinder so that it sits over each piston and soaks in.

A 1/2" drive 28mm socket should be all it takes to turn the crank back and forth just little bit with that mixture in place. Unless of course, it's one of the obnoxious little crank bolts that looks like it take giant screwdriver instead of a socket. The M189s have those.

-CTH

[kelf]

Thank you all for your help! The head is off, and boy oh boy. I'm not sure even Kroil will help. There's thick crusty rust on the cylinder walls. In fact one cylinder had a puddle of water in it, and it looks like it's been busy rusting for years because there's a nice rust ridge about 1/4" thick above the water puddle.

Seems like it would make sense to just find a rebuilt short block, but this engine is a little odd - I'll post a question on a separate thread.

Thanks again...

Kelly

[skalie]

If Kroll doesn't work, try Coca Cola.

Friend of mine unseized a tractor engine by pouring it into the cylinders.

BTW, there's a couple of buses like yours running around my town, one the same colour as yours, the other a fire-engine. If I get a chance to speak to their owners, I'll ask them if they go online, and if so, link them to your bus.

[kelf]

Thanks! I appreciate any contact that might be available.