Clamping Pressure

[GT50]

I have a small block V8 350, my idea was to change from bolts to studs.
The heads are given a prelminary torque of 30 Nm then for the short bolts 55 degrees, medium 66 degrees and long ones 75 degrees.
Is the ARP studs better then the bolts for clamping load?

[mag2555]

Yes, better clamping with studs, but with that being said I have run 10 psi of boost with just ARP bolts without issue.
Depending on the motors power level if your going to detonate then even with studs then only a O ringed deck will help!

Studs can be a pain in a tight engine bay also!

[miniv8]

Take care where you want or think you need more clamping.
Regardless what the stud is rated at, that is just it, a studs rating, it does no apply to what the components need or can withstand of stud pull, or clamping force.
Don't forget that with the same torque setting as standard, added clamping pressure comes from finer threads on the nut for the stud.

[ProPower engines]

I have a small block V8 350, my idea was to change from bolts to studs.
The heads are given a prelminary torque of 30 Nm then for the short bolts 55 degrees, medium 66 degrees and long ones 75 degrees.
Is the ARP studs better then the bolts for clamping load?

This must be a later vortec engine. yes studs torqued to 70 Ft lbs as recommended by ARP will almost double the clamp load.
The later model torque to angle bolts do not provide the same clamp load as the studs will when done in 3 steps.
I prefer to do up all the nuts then in order loosen then go straight to 70 Lbs in a single pull to remove some of the extra friction torque loss when doing them in stages.No more head gasket issues in the later engines that way when using stock head castings.

[GT50]

Thank you Gentelmen for taking the time to answer my question.
The reason for my question was because acording to tests done by Mr. David Vizard in his book " How to Buld & Modify Chevrolet Small - Block V-8 Cylinder heads" page 122 figure 12-4, the studs with their fine threads for the nut did not produce the higher clamping loads.

[MadBill]

Surprisingly, there appears to be some disagreement in Cyperspace on the subject. The clamping force spreadsheet here (as well as others I found): http://www.engineersedge.com/calculator ... e_calc.htm makes no mention of thread pitch.

However, this site: http://www.katonet.com/article/coarsevsfine.html says: "Fine threads require less tightening torque to develop equivalent preloads to the corresponding coarse thread bolt sizes."
More research or an authoritative S/T source required..

[modok]

If they don't include the threads in the calc then it's clearly screwed up.
perhaps you should contact them and set em straight.

Yes finer threads will produce more clamping force at the same torque, all else equal. the principle of "leverage"

[ijames]

Surprisingly, there appears to be some disagreement in Cyperspace on the subject. The clamping force spreadsheet here (as well as others I found): http://www.engineersedge.com/calculator ... e_calc.htm makes no mention of thread pitch.

However, this site: http://www.katonet.com/article/coarsevsfine.html says: "Fine threads require less tightening torque to develop equivalent preloads to the corresponding coarse thread bolt sizes."
More research or an authoritative S/T source required..

If you go to that calculator page and then click on the equations button, you find: "This relationship is based on the assumption that regular series nuts and bolts with rolled threads are used, acting on surfaces with industry standard thread pitch and flank angle." I use a program called Engineering Power Tools for lots of things like this, freeware for a decent version and shareware ($50, I think, worth every penny) for a much more full featured version. Want to know how much stiffer a bigger pushrod will be, how much a beam will deflect or hold, unit conversions, air pressure drop through pipes when laying out your air compressor and plumbing, standard sizes of sheet metal and structural beams, etc., etc.? It explicitly asks for thread pitch and using standard coarse threads it agrees with the engineersedge calculator. As modok says, fine threads at the same torque will produce more clamping force. http://www.pwr-tools.com, just a well satisfied customer, ymmv, yadda yadda

[Racerrick]

head studs are waste of money and time. Bolts are all you need unless you're running lots of boost or nos

[user-23911]

head studs are waste of money and time. Bolts are all you need unless you're running lots of boost or nos

Unless you're in the business of selling parts.........in which case they're essential.



Even if you're running boost........you don't need them because , more often than not, the bolt isn't the weak point, it's the head.
Particularly if it's a Ford.
Or anything else which uses 4 bolts per cylinder, as in one in each corner, 10 per side in a V8.

[Geoff2]

The benefit is in the improved fastener material. With main brgs, you want the same clamping force that the block/caps were machined with. The stronger steel will [ hopefully ] retain the torqued tension, & not stretch like a lesser quality fastener will.
Similar deal with head bolts or studs. You want the same torque applied, but the better quality fastener will hold it's tension better under extreme load.

[mag2555]

Also in my book if your heads are Aluminum there Deck surface needs to be cut mirror smooth so when they expand and contract they slide on the gasket and not rip it up as always happens with a give number of hot and cold cycles!

A wet type milling machine is best for this.