Got a quick question on torque specs. I am about to button up my engine, and I am curious about the torque specs on SBC ARP main studs and Head studs. I have conflicting information. On the instructions with the studs, it calls for 85lb/ft with 30 wieght. I also have a Universal Chart from ARP that calls for 110 lb/ft. The 110 seems high, and I used the 85. Just wanted to see what you guys torque these to.
I have always used 70 with bolts or studs/with the threads oiled. Of course, it does depend upon what type of stud you are using. If ARP recommends 85, that's what I would use. 110 is too much. A waisted stud {like the ones you use on 18 degree heads require alot less}
70 is what I torque my mains to also. I use a different torquing sequence than what most manuals call for. I torque in three stages, I snug all fasteners to finger tight, then torque all of the long fasteners from the center out to 30 lbs, then I will go to all of the shorter bolts that are on the outside of the head to 30 lbs from the center out. I then go to 50 and finally, 70 lbs. I'll run the engine in, and re-torque the head bolts. Make sure you don't over-tighten the studs into the block, they can cause cracks if they are tightened too much. I use blue pro-lock, and only go to about 5 pounds on the studs.
Yeah, I only went finger tight on the block side of the studs. I thought 110 was way off the chart. ARP recommends 70 with moly lube, and 85 with oil. The oil does not protect from friction as well I suppose, so it takes more torque to load the bolt.
Chris
[ January 18, 2003: Message edited by: TurboS10 ]</p>
Remember the torque required for the fastener in question is determined by the block not the fastener, your ARP stud is far stronger than any cast iron internal thread. Of course how much torque you preload any fastener to is dependant on three factors;
-Length of the fastener.
-Diameter of the fastener.
-Lubrication of the fastener.
-Lenght of engagement of the fastener and UTS (Ultimate Tensile Strength) of the material the fastener is holding/engaging.
As you have found out your ARP studs are capable of higher torque loadings than the original bolt due to it's higher tensile strength. I suggest you leave the torque value the same as stock, your new stud has a much higher "spring" value than the original and will provide more clamping force under loading. You could go up on the torque to utilize this strength but you risk pulling the threads out of the block and also distorting the bore if it was not align honed with the new studs torqued in place at the higher value.
I have already torqued them to 85 with no problems. If the block pulled at all, it was not enough to influence the main bearings. Crank rotated smooth as glass after all the main studs were torqued.
While we are on the topic, do any of you know the proper torque specs for ARP 190,000 psi 7/16 hex head cap screws for small chevy rods. I have not yet torqued the rods because they did not come with torque specs for the bolts, and I have not yet call to get them. I know it is pretty damned high, cause it was hare as hell to break them loose.
The torque value on GM Part Number PN-104011092 7/16" connecting rod bolt is 70 ft # and gives .005-.006" stretch. I dont' see ARP bolts being any higher.
I will add a little something here, and most of us already know it, but the whole advantage to a stud is it's improved clamping loads with torque applied. Alot of the torque applied to a bolt is lost due to friction created between the bolt and the block threads themselves. A guy put on a seminar on fasteners once and he use the term "pull up torque," which is what studs achieve best, as opposed to "pull around torque," which is what bolts tend to do. So, basically speaking, a cylinder head with bolts and 30 wt oil torqued at 70 lbs will not have as much clamping force as studs with 30 wt oil and 70 lbs of torque. Any time friction is reduced, whether it's with the addition of studs, more slippery lubes, or the use of hardenend washers {which I recommend} your actual clamping force will increase as long as you are using the same torque value with a torque wrench. Of course, measuring bolt stretch is the best way to do it, but most of us are going to be using torque wrenches. So, bear in mind that all of these different factors, along with the things 4-jaw mentioned {fastener diameter ect}, type of lube you use, the use of washers ect, will increase clamping force. If all of these things are in use, studs, washers and a lube with a low coefficient of friction, then 70 lbs is all you'll need with a small block, and you'll have alot more clamping ability than stock bolts.
Originally posted by NAIRB:
<strong>If all of these things are in use, studs, washers and a lube with a low coefficient of friction, then 70 lbs is all you'll need with a small block, and you'll have alot more clamping ability than stock bolts.</strong><hr></blockquote>
I completely understand what you are saying about the clamping forces. Are you suggesting that I loosen and retorque to 70 lb/ft? I dont doubt that 70 is plenty, but I also know that bolts or studs should be torqued and retorqued as little as possible to prevent material fatique. Are you saying that 85 may present too much force on the main webbing or threads?
I've always used 70 lbs on the mains, and that's even in 800 horsepower dirt late model engines, but I'm sure ARP knows what they are talking about. You'll have no problems with 70 lbs of torque, that I can tell you from experience, but I've never ran a small block with that much torque spec. If it were mine, I would run 70 lbs, but it's your engine, and I would have to think it will run fine with 85 lbs of torque. Just as long as your bearing clearance seems okay, and you don't have any crank binding.
Bearing Clearance and Crank bind were all A-Okay. On a side note this motor will likely see the high side of 800 HP sometime in its future. Well, that is after I get confident enough with 650 to 700 in a short wheel base truck and it becomes not enough. Then....well, A bigger turbo will be in order.
Just recently hit the same problem having 2 diff specs for head bolts ARp bolts stated 85 lbs and the heads I was using call for 65 lbs so I contacted both ARP and Edelbrock and they both agreed that I should use the 65 lbs the heads called for
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