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Does Using Main Studs change the torque requirement?

76zimmer

76zimmer

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This is the first time I've used main studs on an engine, and while checking clearances on the mains, I don't have a torque spec from ARP on them. I used the moly lube supplied, on the washer seat, and the threads, but wondered if they needed to be increased with the use of the studs over the original bolts?
 
Yes, there is a different torque value for studs vs bolts. Not sure of the value difference but there is a difference. Contact ARP.
 
Like Rob said the spec is different for a bolt versus stud. Also keep in mind that when changing to a stud you MUST check the main bearing bore diameter and have it align honed to spec if you find it off (many times just changing from a bolt to stud will change the bore diameter).
 
4X4HIGH said:
Like Rob said the spec is different for a bolt versus stud. Also keep in mind that when changing to a stud you MUST check the main bearing bore diameter and have it align honed to spec if you find it off (many times just changing from a bolt to stud will change the bore diameter).
Click to expand...




Absolutely it will. Everything MUST be aligned honed with the hardware your using. DO NOT change it after it's already been aligned bored or honed. If it was done with bolts, use those bolts.

I had a shop screw me over this same issue. I found out the hard way before I knew about it when I was 18 and built my first motor. A big block 396. I had new rod bolts they were suposed to use. They forgot to install them in the rods. So they did all the machine work and I pick everything up. I find they didn't install the new rod bolts. I ask if they can install them. They said sure.

Few days later I pick them up. They won't bolt onto the crank from misalignment. It was not much but enough. Take them back the the machine shop and ask what's the problem. They say it's the rod bolts you had us install. We already align honed the rods with the other bolts, then you ask us to install new bolts. We did what you asked but now there misaligned. It's not our fault. :angry1::angry1::angry1:

Of course I said you should have installed them and align bored/honed them with the new bolts in the first place. You knew they had already been aligned honed so you should have told me we can't do that or we should not do that. I told them I didn't know, THEY were suposed to be the experts. They would not re-emburse me the cost of having them re-done or now re-do them for me. F**KING A HOLES!! They have been out of bussiness for years. With work like thet I'm not supprised.
 
We decided on the studs early on, so he align honed the mains with the ARP studs in it, I think that is why I don't have the spec....it probably is sitting in his trash can somewhere....He give me the box, and the studs, washers, and nuts in a Ziploc, but no instructions....I know they should have them, because the rod bolts have an instruction sheet with them on proper technique for tightening them.
I will call him tomorrow, and see what he says, I'll contact ARP by email tonight...
Thanks again guru's.
 
4X4HIGH said:
Like Rob said the spec is different for a bolt versus stud. Also keep in mind that when changing to a stud you MUST check the main bearing bore diameter and have it align honed to spec if you find it off (many times just changing from a bolt to stud will change the bore diameter).
Click to expand...

I remember that same response from last year when I asked the question too Scott. I had bolts in my Vette motor and was contemplating studs, and asked that question then. I did fortunately remember your answer for this build :bow:....see an old dog can learn new tricks....:D
 
Call the shop that did the work and ask what THEY torqued the nuts to. It doesn't matter what ARP says since the nuts have been torqued and the mains align honed you MUST use the spec that the shop did when it was align honed.
 
4X4HIGH said:
Call the shop that did the work and ask what THEY torqued the nuts to. It doesn't matter what ARP says since the nuts have been torqued and the mains align honed you MUST use the spec that the shop did when it was align honed.
Click to expand...

good one Scott, that makes sense...replicate the fastener load when it was honed...got it.
 
Just talked with my machinist at home, he said the torque is written inside the lid of the box (110), and to use moly paste that came with them.
I guess I should've looked a little harder.:crazy:
 
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