For those that say I don’t give any attention to the anemic 3FE boat anchor, well here you go, it’s getting love. On the 3FE motor, the front two head bolts are also used to mount the air pump. Those two bolts are NLA. Used are either in poor condition or very spendy...for used.
These head bolts are CNC machined, heat-treated 17-4PH stainless.17-4 stainless is a super common alloy and pricing isn't cheap but its reasonable. The yield strength of a grade 8 bolt is 130,000 psi while the elongation is 12% and Rockwell C hardness is 33-39. The elongation value is extremely important for fasteners. Around 10% is a good and safe number for a bolt in this application. Basically elongation is a measure of how much the bolt will yield (stretch) before failing which is the ultimate tensile strength, 150,000 psi for a grade 8 bolt. A low elongation value material is something like a ceramic. The point where it yields is almost exactly the same point it fails.
Just a little additional information- The yield strength is the point where the material goes from the elastic to plastic deformation. Elastic deformation is the region below the yield point where you can stress/bend material and once you let go it returns to its original state. Plastic deformation is the region where you have stressed the material past its yield point and are now permanently deforming the material. Once you let go there will be some spring back towards normal but the original state or shape is now altered. The top of the plastic deformation region is the ultimate tensile strength where the material shears, breaks, fails.
Torque: 90 ft. lb.
Sold Individually, only two needed per engine.
MADE in USA