ARP head studs or bolts?

[zachm611]

i am in the middle of a build and the short block is pretty much all taken care of. i have a few questions, first of all which size mhg should i go with? .012 was taken off the block and .010 was taken off of the head.

second question is, what is the difference between arp head studs and head bolts, which is better? the bolts seem to be a little bit cheaper, would i be safe to use them? my long term hp goal is probably around 400 most likely a little less though.

thanks for the help,

Zach

 

[pimptrizkit]

safe to use bolts yes, but i would retorque them after 10-20 heat cycles.

the head stud's i perfer, alot easier i think, i can pre-install them or put them in after the head is on. i have heard better thoughts about the studs then bolts.

i belive you should be fine for a 1.2-1.5mm range. thats not much you needed to have milled it seems; i could be wrong.

 

[Jason T]

i am in the middle of a build and the short block is pretty much all taken care of. i have a few questions, first of all which size mhg should i go with? .012 was taken off the block and .010 was taken off of the head.

second question is, what is the difference between arp head studs and head bolts, which is better? the bolts seem to be a little bit cheaper, would i be safe to use them? my long term hp goal is probably around 400 most likely a little less though.

thanks for the help,

Zach

ARP BOLTS same style as stock will come loose and need to be retourqed

APR STUDS with seprate nuts are a set and forget item

 

[Poodles]

ehhhhhhhhhhh WRONG...

both need to be retorqued, and the studs will back out worse usually...

Unless you want a BHG, do the damn retorque it doesn't take ANYTHING to do really...

The studs load the block better and put less wear and tear on the threads in the block. You will have to clean the threads in the block with a blind tap (one made to go into blind holes, in other words ones that don't go all the way through). I tried using a thread repair kit but the tool snapped. Tap is really the only way.

Studs HAVE to go in all the way, and should go in finger tight. If they don't bottom out, then the threads aren't clean enough. Studs will hold the gasket in place, make the head easier to put on (have to put the washers in the head first, if one gets out of place you can pull the stud out and put it back in if needed).

Torque to required value given by ARP with their lube. 500 miles later, retorque.

Enjoy your ride.

 

[starscream5000]

How much was taken off of the head and block? We need a proper measurment to give you advice on the HG to go with.

 

[zachm611]

.012 was taken off the block and .010 was taken off the head. i posted it in my first post, sorry my grammar isnt very good so it was probably hard to read.

 

[Shytheed Dumas]

Isn't it true that removing the head while the engine is in the car is a SERIOUS pita with studs? If you thoroughly clean and lubricate the threads, torque and retorque, are you really gaining anything with studs?

Has anybody done a meaningful statistical analysis of HG failures between ARP bolts and studs to make anything more than an anecdoctal determination that studs are really better than bolts?

I'm not trying to make waves, but I've looked at these threads for well over 1 1/2 years and I would love to see some real numbers put to the "fact" that studs are better than bolts since I'm working on a build and want to make the best decision. Anybody?

 

[zachm611]

yeah me too, im stuck at the HG and stud/bolt part now really, my short block is pretty much taken care of, probe pistons, going with stock reconditioned rods with arp bolts, crank has been cut .010 and polished, going to start putting it together tomorrow after i clean out all the dust and everything from the honing of the cylinders for the pistons. mi getting excited lol.

 

[Shytheed Dumas]

FWIW Zach, I did my BHG repair with bolts, Toyota HG and virtually no experience in heavy engine repair. I've had nothing but success for the entire year and a half since, and the last four or five months have been under 10 to 12 psi boost. To hear a lot of people talk, I would have blown the gasket long ago, but so far the only problem I am having is with my valve seals and/or guides, hence my current build.

Based on conversations I've had with one of our more respected members who is running considerably more boost on a MHG and bolts, you are no better off spending your money on studs, but on quality block/head machining and an HKS HG with ARP bolts. I'm still waiting for some meaningful numbers to show that money would be better spent on studs...

 

[GrimJack]

Bolts would be fine. That said, studs > bolts.

 

[Shytheed Dumas]

I'm not trying to pick Grim, because you are somebody I'm not likely to question, but based on what? A basic 2 sample T test would say whether studs>bolts, studs=bolts, or studs<bolts. Has anybody ever done this work? I couldn't find anything that ARP publishes or anything else that proves that studs are statistically better than bolts.

If I missed something I will definitely go with studs, but based on price and ease of head removal/installation, I plan to go with bolts until I see some numbers.

I can't help it... I'm a numbers guy.

 

[zachm611]

yeah, i really dont trust the engine in my car right now it was supposedly "rebuilt" and not running but after i got it running it had bhg, and when i took the head off you could see it was not torqued down in sequence it looked like it was torqued from the back up. and my car DEFINITELY should have a bhg as i did not have any machine work done to the head or block, the head looked like it was milled with a belt sander lmao, but i put a felpro gasket on and re used stock bolts and have had no problems with it. i too run 10-12psi. my main reason for a build is i want something reliable and thats been done right so that i can trust and still have potential for a little more power. and im thinking about going the studs route just because it seems everyone says they are better, but i am very curious. is the head a PITA to get off with studs installed?

 

[Shytheed Dumas]

I'm not going to make a decision on a single situation, but if even one person can show that reused stock bolts retorqued in the wrong sequence on "sanderbelt" surfaced head/block and composite HG (i.e. worst possible situation) can reliably survive 10-12psi, it makes me wonder what really matters...

A while back there was a poll that asked for degree of head and block machining and type of HG, but nothing on bolts/studs. I ran the statistics and had one of the six sigma blackbelts I work with go through the data as well. The data were definitely not ideal, nor were they balanced. I need to dig the thread up, but there were some surprising results that contracted some of the truths I see all the time.

I don't doubt the experiences people have had, but I wish there was actual proof of some of these things.

 

[GrimJack]

Ok, I'll elaborate a bit.

First of all, I've re-used stock bolts at 14 psi without any problems. Well, no problems due to the head bolt torque, anyway, they held while I blew up some stock pistons...

So, really, anything ARP is overkill to begin with. Now, again, keep in mind that the difference in cost between stock bolts and ARPs, even if you're going to re-use your stock bolts, isn't very much. For the $100, you'll have a hard time buying better insurance OR peace of mind.

As to why studs are better... there is no difference convenience-wise, the studs will go in and out with the head on the car, just the same as bolts. There are allen key cutouts on the tops of them to make it easy to pull them while it's still on the car. They are better mainly for three reasons. The studs are tougher than the bolts, or at least ARP says so. When you torque the studs you get a more accurate reading because the only friction is from the nut to the washer / stud - zero flex there, and you're talking about literally perfect threads. On bolts, you are adding friction from the less than flawless block threads, the bolts can flex during torquing, and it's possible to get junk in the block holes that will play havoc with your torque readings. Furthermore, the surface contact area on the stud nuts is larger than the bolts.

 

[Poodles]

These are the main reasons the studs are better...

The studs load the threads in the block differently. You're applying a twisting action and a lead on the threads with bolts. This only loads a small section of the threads. Studs load the entire surface and don't twist. This prevents stripping of the threads.

The studs go all the way into the block using ALL of the threads. The bolts only go HALF of the way in.

Overall the studs are a far stronger and more durable solution.

 

[3p141592654]

The studs and bolts both use 190,000 psi material, and are both 12 mm. Due to lower and more consistent thread friction, the torque spec for studs is 5 ft-lbs lower than bolts.

Attached are the instructions for bolts and studs if you don't believe me.

 

[starscream5000]

.012 was taken off the block and .010 was taken off the head. i posted it in my first post, sorry my grammar isnt very good so it was probably hard to read.

It's not that, what are you talking about? Inches? Milmeters? You have no system of measurement after the numbers, but I'm assuming you are talking about .012" and .010" respectively...

 

[zachm611]

sorry i forgot the inches yes it is .012" and .010"

 

[flubyux2]

on the retorque... alot of people misunderstand it.

after corresponding with an ARP fastener rep, i was informed that ARP fasteners do NOT need to be retorqued after engine run-in.

the "retorque" that an ARP fastener needs is BEFORE the engine is ever run.

essentially, what you need to do is torque the new fasteners with the proper lube, in the right sequence, in the 3 stages suggested. Then, reverse the ratchet and loosen the fasteners in the proper reversed-sequence. Then, Repeat the torque pattern in the proper stages. Reverse the rachet and loosen the fasteners again in the proper reversed-sequence. Then, the 3rd time is usually accepted as the Final torque. of course, you do it in the proper pattern in the 3 stages.

why do you do it this way? because, a singular torque'ing as most people do does not transmit the full torque yeilding in the necessary stretch of the fastener.

why the hell not, you ask? because the black-oxide coating on the threads of ARP fasteners creates friction and the torque required to overcome this friction prevents the fastener from getting the necessary stretch to approach its designed load.

So why the hell do they put it on there? because, its prettier and prevents oxidation. it preserves the loading surface of the threads so its pristene when it comes time to install the fasteners.

Ok, but why the multiple retorques in one sitting? Because, torquing the fasteners wears off this black oxide coating and creates a matching surface between the loading faces of the threads on the fastener and its mating counterpart. The more you torque and untorque, the more these faces "break in" and burnish against eachother creating a smoother and smoother surface. youll notice what i mean when you look at Used ARP's and see that the threads have turned silver and only the throats of the threads are still black-oxided.

the same reason people seem to say that arps need retorqued after engine run-in is probably the same reason 7M's blow HG's when stock; lack of sufficient torque to create the necessary stretch on the fastener. when its not completely "tight", the heating and expanding can create slack in the fastener which would allow it to back out over time... which explainse why ive taken apart stock motors where the bolts were only hand/finger tight.

also, the statement about bolts being inferior because of block-thread engagment and questionable thread quality in the block is 100% correct. ive seen block-threads that essentially looked like a spiraled version of a Dayco Cogged serpentine Belt. the threads were definitly flawed and oxidized. no matter how many times i ran a thread chaser in these holes, the bolts still hung up to some degree when hand-threading them in.

 

[Poodles]

nope, I did that exact process and I still did the retorque and they had backed off...

IJ did this as well