benhart16
Well-known member
Greetings everyone.
After reading that the PD150 stock head bolts are grade 12.9 (174,000psi minimum) and that they can be used as an upgrade over the stock 10.9 bolts for the ALH engines simply by trimming them down to 115mm, I got to thinking. I also read that there is less friction variation when torquing a nut on a stud than when torquing a bolt into the block, therefore studs are recommended for heavily modded applications.
The question in my mind: Is is better to trim the end of the bolt off and use it as a bolt, or to cut the head and smooth shank off and use it as a stud?
From the pictures it looks like the threads are more than 115mm long on the PD150 bolts. If I used PD150 bolts as studs, would I still use the same torque sequence as the bolts, torque to spec, then 90*, then 90*? I know the PD150 bolts are torque to yield, so I'm guessing they would still stretch when used as studs.
Background:
Ever since I realized that ARP uses 8740 steel (heat treated to 180,000 psi) for their studs while charging around a couple hundred bucks, I have wanted to search for an alternative that would be equally effective, yet a fraction of the cost. After doing a bit of searching I realized that grade 12.9 bolts are nearly identical to the ARP 8740 studs in terms of tensile strength, but at a fraction of the cost. I have not yet found a mandate on the alloy used for 12.9 fasteners, other than to say it has to be vanadium, molybdenum, or chromium.
After reading that the PD150 stock head bolts are grade 12.9 (174,000psi minimum) and that they can be used as an upgrade over the stock 10.9 bolts for the ALH engines simply by trimming them down to 115mm, I got to thinking. I also read that there is less friction variation when torquing a nut on a stud than when torquing a bolt into the block, therefore studs are recommended for heavily modded applications.
The question in my mind: Is is better to trim the end of the bolt off and use it as a bolt, or to cut the head and smooth shank off and use it as a stud?
From the pictures it looks like the threads are more than 115mm long on the PD150 bolts. If I used PD150 bolts as studs, would I still use the same torque sequence as the bolts, torque to spec, then 90*, then 90*? I know the PD150 bolts are torque to yield, so I'm guessing they would still stretch when used as studs.
Background:
Ever since I realized that ARP uses 8740 steel (heat treated to 180,000 psi) for their studs while charging around a couple hundred bucks, I have wanted to search for an alternative that would be equally effective, yet a fraction of the cost. After doing a bit of searching I realized that grade 12.9 bolts are nearly identical to the ARP 8740 studs in terms of tensile strength, but at a fraction of the cost. I have not yet found a mandate on the alloy used for 12.9 fasteners, other than to say it has to be vanadium, molybdenum, or chromium.