cat head bolts

.004 is on the low side of spec. Could be anything. Stretched bolts, holes not cleaned out. There were some 6NZs that left with the holes not drilled deep enough. Improper torque....many things

 

They cut the deck and the head(raising compression)? Did they cut the counter-bores? Did you SEE the .004 on every hole or is that what you were told? Not looking for an argument, or pointing any fingers I'm just saying that most(not all) head gasket problems can be traced back to a liner or installation problem. Did they use the old headbolts when they rebuilt it?

 

What he said.....I would verify if they counterbored or not and prove protrusion measurements. Cat bolts don't usually stretch unless pitted. I've never replaced head bolts and never had issues but anythings possible.

 

Almosdt everytime when a head gasket blows repeatedly it is because the liner protrusion is not even all around the cylinder and the protrusion of the liner next to it is too high. You should have around .006 liner protrusion and no more than.0005 from side to side on each liner with no more than .001 difference across all liners. There is a thicker head gasket that you can order but that has to be taken into consideration when cutting the deck. Head bolt holes that haven't been wire brushed out will also effect the torque. If they didn't use cat head bolt lubricant then the torque won't be sufficient.

 

IIRC the thinner plate is .003 thinner, making you .007 protrusion which will crack a liner flange.