Moparts Tech Archive
Big Block
Another ??? on main studs.
I had a conversation with STEFF today about a discussion he and Todd440 had. Lets see what the general concensous is. Are the torque values different when studding the mains as oppossed to using main bolts?? And, If your block is align honed with bolts, must it be re-align honed if you change to studs??
My opinion on this is no and no. Tight is tight. The main wont know if it is 80 ft. lbs of torque with a bolt or stud. Also, if the block is align honed with a tightened down main cap, again, a stud is just another means of tightening it down..
Anyone care to chime in??? I'm certainly no machinest.
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I used ARP main studs in my 440 boat motor. Torqued them to ARP's spec using their lube.
My machinist had me leave my studs with him for align-hone; said the studs thread all the way to the bottom of the hole, thus distorting the block more than regular bolts.
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the ARP instructions say the block has to be align honed after installation......I thought about not doing this too, but chickened out and had it done.
......I just ran out into the garage and checked the ARP studs instructions. They call for 90 lbs of torque with ARP moly lube...or 130 lbs of torque with 30 wt motor oil. So if they were honed with less last time...maybe that could make a difference?
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My take for what it's worth,
Studs have a non-threaded base which alligns the cap concentricly on the stud, bolts basically float through the holes in the cap. Studs also have fine threads and washers so the torque value/load Applied to the cap per 360 degree turn of the torque wrench is not exactly the same.
If it's a motor I'm gonna stand on pretty hard, like a stick car (or a high stall 3600lb Challenger with a killer set of Eddy's that might dip in the 10's)
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As Wize said, the stud helps line the cap up, a bolt does not. You don't use the factory torque spec with the studs, you use the fastener manufacturers rec, which is usually a good bit higher than stock specs. There are two schools on putting the studs in the block, some suggest loctite and give a torque spec, others say finger tight only. Either way, I would not switch between the two without a line hone. No need to risk a good motor over a $150.
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well, you can take this for what it's worth i suppose.
you need to align hone the block when using studs. the torque values are different because the fasteners are different. with that the increased torque will distort the block differently but more importantly the main caps will distort much differently with the increased torque value. if you want proof, use a dial bore gauge and torque a main to 90 ft lbs. then torque it to 130 ft lbs. you'll see the difference. tight is not tight as you say. the reason for the higher torque is due to the fasteners load rating. it needs to yield in the 80% range so it stretches the fastener. if you don't do that it will come loose. as far as the installation, that's just personal preference. i install them with loc-tite 271. the main reason for that is so the stud doesn't turn in the threads while doing mock-ups for bearing clearance etc. since they might be taken off several times during the process. i also like to tighten them to about 30 inch pounds, if the taper on the block isn't right i make it right so no chipping,flaking or cracking takes place later on. it's just something that works for me and a personal preferance though.
Here's another...if the block is true with the bolts and then you install the studs and mic it, and it's still true, does it still need to be aligned honed? If the bearing fits mic true when it's torqued to specs, I don't believe it needs the added cost. I don't install the studs tight into the block either, just snug but if you did make em tight, how tight are you making them to distort the block? And if you do distort the block with em, are you machining the faces where the caps mate too? And doesn't the block locate the cap side to side? If the thrust bearing/cap isn't installed properly, you'll wipe it out no matter what kind of bolts/studs you use. If the studs/bolts interfere with the caps, you must make clearance. If the studs locate the caps, yeah, you'd better alignhone and then make sure the studs never move again. I think some machine shops are doing alot more work than what's needed or are not taking measurements during assembly/machining and you have to check before assembly and during. Does anyone ever mic the top end of the cylinder after the head is torqued on? Yeah, ya gotta go from the bottom up but I've seen shops claim to use a deck plate and not do it! The last alignhone job that I got back was worse off than it was when I took it in. If you don't measure this stuff, you are shooting in the dark and hoping for the best. just my .02
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