Head rebuild problem

[Bo82CB]

That old gasket looks very weird, that thicknes difference is pretty big!
Have an idea, if you can put very thin layer of poweder or some chalk powder (like used on straight line rope) on the top of your pistons and install head. When head removed maybe some will be left on the valve if your problem is piston to valve clearance!? That "new" head gasket is junk anyway due to multiple tightening and loosening...
What you all think!?

 

[dirtdigger]

About the only reason to double the base gasket would be to raise the cylinders. Maybe the cylinders at some point had been machined to far on the top so they need more piston to cylinder head clearance. Double the gasket is not a good way of doing it but I am not seeing much for thicker base and head gaskets. I have several options on sohc motors but I dont mess with the dohc stuff. The way to check is to mock up a cylinder with base and head gasket, piston in without rings, put a little clay or playdo across the piston and put the head gasket and cylinder head on, rotate the engine, pull the head and see where and what is hitting. Then you can determine how much difference you need to make up to make the correct piston to head clearance. You may check with cyclex see what they have for gaskets or they might know where to get some.

 

[Andy novice]

Put a layer of grease on top of the pistons and rebuilt the head turned the engine both ways between the 2 ends of travel where it jams.
Striped the head down for about the 7th time. no grease anywhere other than the tops of the pistons.
I am at a loss as to what to try next. HELP

 

[dirtdigger]

If it spins without the head but doesnt with the head then it has to be piston hitting the head, nothing else it can be. The piston edge is more than likely protruding past the top of the cylinder at top dead center and hitting the head or head gasket. I would doubt any of the dome is hitting anywhere. The double base gasket is first suspicion that the pistons protrude, someone shade tree "fixed it with two thick base gaskets. If you can determine that it stops rotating at top dead center then you know for sure it is piston to head contact. put it back together but dont tighten the head nuts and the head will probably lift ever so slightly when you rotate it.

 

[Bo82CB]

...or if you can make few spacers in the thicknes of old gasket and put under the head when mounting on the block. This will allow you to see what gets close to what contact wise. DO NOT TORQUE HEAD.
If it turns with out problems you have your answer.

 

[81cb750f]

Did you solve the problem? Only thing I was wondering after reading the above thread was; as you are rotating the crank to turn the engine, are you holding the timing chain up as the chain will move also? If not, the chain will bind in the bottom of the engine at or close to the crank. The chain goes down through the head, then the block, and then around a sprocket on the crank. The space gets quite small as it goes down so the chain can easily bind or bunch up down there. I usually attach the chain to the hook of a bungie cord and then have the bungie cord attached to something above the engine. That way you can rotate the crank without having to worry about the timing chain as it will rotate as well. Its also possible that it is already bound up close to the crank and only has about a 1/4 turn of play before it gets stuck.

 

[Andy novice]

Thank for taking an interest.
I have proven that it is a gasket problem and that at some point in the past the head must have been schemed. I have now sourced some thicker gasket to make my own and see it it works.