Installing Valley Head Bolts/Studs on a Big Block Chevy
Since it's almost impossible to find this information without 3 or 4 phone calls, along with varied opinions on "what" to use I decided to document just exactly what it takes to install the valley head studs/bolts on a Dart Big Block Chevy.
First of all, you'll hear different opinions from people on what to use - many engine builders use allen head cap screws for this. However if you talk to Rehr Morrision or Dart, they highly recommend the use of Dart Head Stud Kit PN# 64210240. That kit should retail in the $90 range, no, it's not cheap but after looking around at other options it does appear to be the best way to do it. The kit contains (4) 7/16-3/18 step studs, 4 washers and 4 "shoes" that fit nicely into the registers on the Dart block.
ARP will try and sell you 7/16 Studs for this application, BUT you'll find out that after you get them in there is no way to get a wrench on them or a socket. You must use a 7/16-3/8 step stud to gain clearance for the nut in the block valley or you'll need to grind clearance in the block to clear a straight stud and it's nut. Don't bother, just get the Dart Kit it's the way to go. It's likely you may have to grind a little bit of extra clearance on the radius of the shoes, but it shouldn't take too much to clear the block. Just make sure the shoe sets squarely in the block register when you're done. You'll also likely have to grind a small flat on one side of the washers in order for those to clear as well.
Next you'll find out that you can not get a torque wrench underneath the stud to torque the nut down, so you'll either need to buy a 12 point crowsfoot extension, or make your own. I made mine using one of my good craftsmen box end wrenches and a socket. From the center of the box end opening to the center of the socket, it is 3" long - that dimension is important because you'll need that much to clear the cylinder head for the torque wrench.
When it comes time to torque the nuts, you'll have to change your torque wrench setting to get the correct torque because the wrench length creates additional leverage and will throw the torque values off.
The formula for the adjusted torque setting is as follows:
Torque Wrench Extension FormulaT1 = T2 x L1 / L2
T1 is the torque setting of the torque wrench.
T2 is the actual torque applied to the nut.
L1 is the normal length of the wrench.
L2 is the combined length of the wrench.
Example: On my application I wanted 50 ft. lbs. with oil, my torque wrench is 16.5" long from the
center of the head to the center of the handle, and my wrench extension is 3" long
50 ft. lbs. x (16.5/19.5) = Set wrench at 42.307
I hope this saves somebody a bit of time chasing down things for their engine build...