Here is what I found when I removed all 10 main bearing cap bolts from my L76 engine.
3 bolts: "N" inside single circle.
2 bolts: "TR" inside single circle
3 bolts: "TR" within 4 radial lines set at 0, 90, 180, 270 degrees
3 bolts: "M" with 4 radial lines set at 0, 90, 180, 270 degrees.
1 bolt: "TR" with 4 radial lines set at 0, 90, 180, 270 degrees.
I have bought 5 new bolts from GM, which are marked with "O" with 4 radial lines set at 0,90, 180, 270 degrees.
I have bought 5 new "stud/bolt fasteners", which are marked as pictured. These are to install a missing windage tray.
I have looked at numerous SAE, and ASTM publications, but cannot find any correlation to neither a single circle nor a "4 lines" headmark. I assume that these fasteners are at least Grade 8. Does anyone have any further info.
I understand that common grade 5 bolts have 3 radial lines @ 0, 120, 240*
Grade 8 have marks @ 0, 60, 120, 180, 240, 300*.
Thanks in advance.
Joe
3 bolts: "N" inside single circle.
2 bolts: "TR" inside single circle
3 bolts: "TR" within 4 radial lines set at 0, 90, 180, 270 degrees
3 bolts: "M" with 4 radial lines set at 0, 90, 180, 270 degrees.
1 bolt: "TR" with 4 radial lines set at 0, 90, 180, 270 degrees.
I have bought 5 new bolts from GM, which are marked with "O" with 4 radial lines set at 0,90, 180, 270 degrees.
I have bought 5 new "stud/bolt fasteners", which are marked as pictured. These are to install a missing windage tray.
I have looked at numerous SAE, and ASTM publications, but cannot find any correlation to neither a single circle nor a "4 lines" headmark. I assume that these fasteners are at least Grade 8. Does anyone have any further info.
I understand that common grade 5 bolts have 3 radial lines @ 0, 120, 240*
Grade 8 have marks @ 0, 60, 120, 180, 240, 300*.
Thanks in advance.
Joe
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