Linhai 257: 1) Head Repl Leaks AF Joint w Block 2) Won'tFire  By  bob123456789 (Read 2,867 times)

it isn't just the matter of fitting, the dowel pin cavities might not be deep enough to accommodate the pin.
the only way i know of to check this is with a "t-square" type of micrometer.
the dowel pin height should be less than the cavity depth in the head.
if it is too high, then you might try tapping the dowel further into the block and measuring again.
if that doesn't work, then file off the tops of the dowels just a little, and measure again.
take this measurement without the gasket installed.

if you suspect the acorn nuts are the source of your problems, then you might want to get some replacements.
i'm sure some of the local parts dealers can give you some options.

i just wished i could credit the person that turned me on to the idea.

But they look pretty.

Test fit the head with the dowel pins in place but without the head gasket and see if the gap that remains is too big to compress the head gasket otherwise you have to measure everything to account for the length of the dowel pins, depth of the dowel pin sockets in the head and cylinder along with the thickness of the head gasket. One quick test is if you can slide the head gasket into the gap near the dowel pins then they are too long or the sockets are not deep enough.

Do not recall if that one has seals on the dowel pins for piping engine oil to the valve train like the Aprilia/Piaggio/Vespa design.

Here are some of the things rockynv asked for:

Old gasket thickness 1.4 mm
Old dowel outside diameter 14.0 mm
Old dowel pin length 15.9 mm
New dowel outside diameter 13.94 mm
New dowel length 15.9 mm
New head:
Dowel hole diameter 13.75 mm
Dowel hole depth 9.0 mm (measured by putting the new dowel in the hole and measuring the amount remaining out then subtracting from the length of the dowel pin)
Old head:
Dowel hole diameter 13. mm
Dowel hole depth 9.0 mm (measured by putting the new dowel in the hole and measuring the amount remaining out then subtracting from the length of the dowel pin)
Block
Dowel depth 8.0 mm
Dowel diameter not available since the stud is going thorough it

My new gasket is too sticky with the Copper Coat to measure or try fitting to test the thickness.

Should I use grease on the dowel pins when I reassemble it this time too help them seat deeply in the holes?

Should I be replacing the head gasket that has the multiple layers with one that is just plastic?

I am not seeing anything real obvious as to why it is leaking oil and antifreeze. Maybe a slight amount of rust in the dowel holes in the block?

Any insight into how to solve this would be really appreciated.

Next steps?

That new gasket does not look right. Where are the coolant ports? Is that a base gasket or from an Air Cooled engine?

Dowel pin holes are 17mm combined mated to 15.9mm pins so that along with the thickness of the head gasket should not be a problem.

Can you show a close up of the head gasket you used along with the same area on the cylinder and head where you saw the leak?

Also on the new head there appears to be a slot in the upper left corner of the picture that is not machined and seems to taper yet its profile appears on one of the gaskets. What is going though with that? Also there are a few ports on the new head that neither gaskets cover so are they blocked off or were screw in plugs provided with the head to block them off?

Here is a pic of the head gasket I have that is spare from a gasket kit I bought. It has not been copper coated yet.

cyborg55. When I put it together last time I was able to torque it to the recommended torque and still had the small leaks.