Head stud question?

[FCnLa]

I bought some head studs for my motor. For various reasons. Thread wear in the aluminium block the most.

The bolts are coarse and the studs fine (on the nut side). What torque should I use? I am guessing less? More torque multipication, right? I will get a threads per inch count and take a percentage and subtract that from the normal torque specs, or does it work like that?

I don't want to over torque. Thanks! :)

[Bill Gohr]

The studs you have probably have no more thread contact than the bolts you took out. If they don't go all the way to the bottom of the block they're not doing anything more than your bolts.

[us1]

I think what he is wondering is with the different ratio in thread pitch should he torque the stud less to get to same amount of stretch. That’s an interesting question that I don’t the answer to. We need a bolt expert to answer this one.

[DaveR]

The reason I use them is that I have stripped enough bolt holes because motors have been apart to much. I got REAL tired of heli-coils. With studs, the block threads do not see the wear / damage of removal and re-torque. I don't do it for any increase in torque.

The fine thread has more surface area, and speaking only of the fastner, it can be torqued to a higher torque than a coarse thread of the same diameter. That's why the stud threads are finer on the nut end. I can look up the proof loads for both threads and post it later, but I still use the factory recommended torque (what - 40 ft/lbs?). The interesting information though would be torque vs clamping pressure. If you went up 5 lbs in torque how much additional clamping force is generated.

[B.Leonard]

I don't recall ever lowering the torque for studs on other motors (4cycle).

As long as the stud is screwed in as far as possible it shouldn't be a problem. Especially for a 5/16 or 3/8" stud, 25 ft lbs for example isn't going to do any damage like pull the stud out.

There is no question the studs will put more force on the heads than bolts and much less stress on the threads in the block. They are the way to go no doubt. They're like insurance, when you have it nothing ever goes wrong.

I'd use some common sense though... On my 2.6 crossflow for example the head bolt holes next to the exhaust chest don't have as much material supporting them. If you notice an area like that where the stud fits loose for whatever reason you might want to rethink your max torque level, or just get the block repaired first.

-BL

[Bill Gohr]

FC's post says his biggest worry is worn threads. As is most peoples reason for buying studs after the block is damaged. The studs he has which sound like land and seas have less contact with the block than the original head bolt. Most people install them and try to bury them in the block which ends up ruining even more threads. Even if you don't screw them in too deep, with the fewer threads, you'll pull them out. Finer threads allow you to torque them more which compounds your problem. The real fix is to use studs which are course threads all the way which allow you to bury them in the block. Commonly 2.5's have about an half inch of unused threads at the bottom. Using course studs allows you to get fresh threads and not have to worry about what the difference in the torque is, and yes they're harder than the original bolts and the stainless ones bought elsewhere. If you want the course studs I have them and so does Chuck Goodman.....

[Superdave]

The head stud "kit" from Land & Sea & others costs around $100.00. I went to a local bolt & screw co. and purchased grade 8 setscrews the proper length, stainless nuts & stainless sae thick washers for less than $30.00 ! The setscrews can be installed/removed with an allen wrench. Seems to be workin fine for me. No salt water here...
Dave

[B.Leonard]

That does sound ugly.

I wouldn't mind using a coarse thread stud (not prefered though), as long as the washer was hardened. The washer should be hardened so the nut won't gall it and so it doesn't bend into the head bolt hole.

-BL

[DaveR]

Goodman sells them for $80. Land and Sea was getting......are you ready?..................$199.00 but they no longer carry them. You suppose the high price resulted in low demand? Can you say "marketing"?

[JTS Racing]

With the purpose of fastners being to obtain a desired service or clamp load with a given bolt pre-load or stretch, wouldn''t the tensile strength be a more important factor than the number of threads?

In most designs, bolts are chosen with their tensile strength and diameter to yeild a 65-75% stress load or "stretch" to the bolt for the needed service load. This keeps the bolt from loosening or failing. Fine threads can yeild a larger stress load to diameter for higher clamping forces when space limits the diameter of the fastner that can be used.

What is the "grade" or tensile strength of the bolts that are OEM? Are the studs of the same grade? If by using a higher tensile strength can enough pre-load be placed on the stud at 40 ft#'s to keep it from loosening and it not pull out of the block :confused:

[BarryStrawn]

A common mistake made when installing studs is to torque them into place. They should only be hand tight. If they don't go in easily then the threads need to be cleaned up with a thread chaser. If you torque them into the block, it concentrates the load on a few threads.

Best stud for aluminum is a coarse thread which fully engages all threads in the block and a fine thread for the nut with a parallel ground hardened washer. If you can't obtain studs in the correct dimension, then the all coarse thread solution makes sense.

ARP will make studs of about any dimension but it will cost more than off the shelf hardware. http://www.arp-bolts.com/media/pdf_files/fastcalc.pdf

They also publish a torque chart for fastener applications including studs in their catalog. May or may not apply for FCnLA's 235. http://www.arp-bolts.com/pages/tech/images/fasttorq.pdf.


Barry

[B.Leonard]

That's a good point Hydro. That is why bolts used in applications where stretch is desired sometimes neck down to a smaller diameter in the body of the bolt to compensate for the high tensile strength of the material used to make the bolt.

The first thing that comes to mind are stock Chevy small block head bolts. They're easy to spot in a box of bolts because they neck down between the head and threads.

The fine thread studs used for head studs are not as much to give the stud more strength as to provide more granularity in the torque. The torque increases more gradually when tightened. This makes it easier to get all studs torqued more evenly.

Studs are really nice where the stud is 1/2" (i.e Ford big Block that has 4 head bolts per cyl) and you need to torque to 100ft lbs. They come up to the desired torque level evenly and consistently and give you much more confidence that they are properly preloaded.

-BL

[BarryStrawn]

http://www.arp-bolts.com/pages/tech/images/fasttorq.pdf

Period broke the link in previous post

[DaveR]

Generally only 5 threads of a fastner carry the load at any one time. If they yield the load is transfered to additional threads. The problem I found with someone torquing the stud in the block was that they actually punched a "button of aluminum out of the bottom of a few holes. I don't know what others are doing, but I go hand tight with 271 high strength loctite.

[B.Leonard]

Yup, that's typically the procedure as Barry noted.

FCnLA... When you do finally decide on a set, let me know where you got em and how they worked so I can get a set for my 2.6XP.

-BL

[FCnLa]

I should have been more clear. The studs have coarse on one end and fine on the other. I would not even think about changing the threads in the block to fine! I just was thinking, more threads per inch will "gear" it down.

Used for a OMC crossflow: Dorman part# wrong damn # When I get the right one, I will post it. Sorry, my bad:( .

[Robert]

I thought the main advantage of a stud was the thread stress was moved from the block to the nut at the opposite end. Clamping force is on top of the head ,no longer at the block.

Loctite at 10 ft lbs and if you wanted to add a little integrity recess the thread below the surface. One engine design(inline) had big studs from the top of the head to the main caps ,so the block wasn't stressed.

If you make a thread repair in aluminum you need to use a Time Sert. It is a solid sleeve about the same dim. as a helicoil but much better strength.

Fine threads have better clamping forces and would probably be in the block if they weren't made of too soft of a metal.

I'll get info monday on the Timeserts

[B.Leonard]

Yeah baby! That'll do it! Thanks for the numbers guys.

Just need to find hardened washers now. Thick steel ones would probably work but the hardened ones are trick.

Robert, the head is being forced onto the block either way, by stud or bolt. It is true that the studs reduce the stress on the threads in the block. That Timesert thing sounds interesting. Never used anything like that.

-BL

[Robert]

The Winzer Corporation is our supplier.
www.winzerusa.com
10650 Markison Rd
Dallas Tx. 75238
!- 800-527-4126
If you make any thread repairs, this product is machine shop quality.
Installs similar to a heli-coil, std or metric, different lengths. (Must be square to the surface). Loctite them in and forget about it.

BL, The best example I can think of is our trailer wheel and hub. Only the lightest duty use tapered shoulder bolts to hold a wheel on.

In steel you want 1 1/2 the dia. of the bolt. In aluminum you want all you can get without bottoming the bolt. Studs are made to replace bolts so they make them with the similar characteristics, unless your bolt supplier hands you grade 5 allthread. Hard to find good help sometimes. Unless you raise cyl. pressure considerably you don't need rod bolt tensile strength.
I'll drill and tap to the next size if I find something that was engineered weak. Then you can use the mass produced bolts off the shelf. Don't use the short hardened nuts.

A friend spent over 3k on Brobex(sp) heads and intake flow benched for his jet small block(all aluminum). They came new with these Time-Serts in all the threads.

Hope it Helps

[B.Leonard]

Brodix heads are pretty good. I recently used a set of those new Edelbrock heads on a Ford 390. Very bad quality and no inserts. Bolt holes for the valve covers were off by inches, spark plug holes were way too tight to get a socket into. I was disappointed to say the least.

-BL

[Robert]

You spend hard earned money and QC is out to lunch. It's crazy!


Sorry to hear that.