Moparts Tech Archive

Motor General

Main studs or bolts?

should i use main studs or bolts for the 422ci small block? it is a mild build 10.75-11.0 compression elde heads solid cam 560/575 lift 245/252@ 0.050 steel crank,h
beams,custom forged diamond pistons.what would the studs do for me that the bolts won't?please teach me what i don't know how would one be of a benifit over the other thanks kevin
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DusterDave
Moparts Member
Posts: 2709
From: Tampa, FL
Registered: Mar 2000
posted 07-04-2002 10:23 PM

Main studs, definitely! Don't skimp on critical fasteners, go with ARP
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jamesc
Moparts Member
Posts: 2870
From: Peoples Republic of New Jersey
Registered: May 2001
posted 07-04-2002 10:26 PM

imho studs are always better than bolts (provided you can use them) for a number of reasons. better clamping,negligible wear and tear on the cast threads. the drawbacks would be head removal (in car) and the common practice of align honing the mains when studs are used. the engine you've listed is not a low buck build so imho it should be honed anyway.

forgot to mention that in some cases the thrust maincap may need the bolt holes enlargend so you can get the thrust faces to line up.
DON'T OVERLOOK THIS
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ZIPPY
Moparts Member
Posts: 4489
From: Detroit suburbs MI USA
Registered: Jan 2000
posted 07-04-2002 10:38 PM

Studs are stronger for several reasons:
-usually they are made from a better material than grade 8 bolts (not that that is a big deal---the stock bolts are already far stronger than the block is....)
-the entire threaded hole in the block is used, as opposed to the bolts which use part of it---the cap "works" on that partially threaded bolt, and the remaining threads in the hole act as a stress riser, making cracks/other damage more likely than if a stud was used
-stronger clamp on the main caps
And there are more that I forgot.

Bolts can more than get the job done but studs can get the job done better!

You will more than likely have to align hone when switching to studs, more times than not the studs will stress everything differently and the bores won't be round anymore with the studs. Sometimes you can get away without it, you need a good dial bore gauge to tell either way.

Drawbacks? Well, in a SB they hit the oil pump alot of times, and you have to grind the pump/shorten the stud or nut to make it fit. So that might take a little while to sort out.

I definitely wouldn't use them in a retrofit kind of deal (you know, take the mains off a running motor and put studs in--that is probably not a good idea), but when building a new/freshly machined/fully machined motor I can't think of any reason not to use them. Always supply your machinist with the studs when it is time for the align hone so he can use them at the prescribed torque during the machining process.
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Fast One
Moparts Member
Posts: 3156
From: Australia
Registered: Nov 2000
posted 07-04-2002 11:56 PM

Later on you might get greedy for more power & if the bottom end is bullet proof it's one less thing to worry about.
Block will need to be align honed.
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