ARP head studs vs. torque to yield - madness

I am beginning to lose sleep over this issue. I have never been led in the wrong direction by listening to the majority of the people on these forums, but, I am starting to re-think my decision on buying the ARP head studs.

I am no engine builder, this is a slightly modified daily driver, and this is my first time this deep into an automotive engine. I have asked a few knowledgable gearheads that I know about using ARP studs on aluminum heads. Between what they have said and what I have read online (not on SCCOA), torque to yield bolts are they way to go (if torqued properly). Due to the fact that Aluminum expands more that steel when heated, the stretch of the bolts always keeps an even clamping force between the heads and the block.

If the ARP studs don't stretch like the bolts do, wouldn't this cause a kot of stress on the heads of a hot engine and possibly crack the heads.

Please feel free to reply, I need to make the "right" decision in a few days when I get my heads back from the machine shop.

ARP's

I'm just past the same place you are. 95 SC, replaced HG's myself, first time into an engine this deep, etc. etc.

In the years that I've been following this board, I have not heard anyone reccomend ANYTHING other than ARP's. I put them on my SC, and other than not reading the 'slight modification required for proper fitting of exhaust manifold' They work well.

If I had to do another rebuild, I'd use the same thing. Again, I'm just a shadetree, at best.. but those are my $.02

Chris

manifold mods?

Chris,

what mods are required for the ARP stud install.??...I am rebuild a SC crate motor with only 35k or so that some guy toasted the #2 piston [plugged injector, my guess] rest of the motor looks sweet, but having built BB Olds
since 1980, The TTY head bolts make my stomach gurgle...so ARP to the rescue....

BTW, found some laser cut steel .020 steel spacers for the 3.8 motor
...with the stud setup, you'd have a hard time blowing that out
Vendor is Silver Seal Products in Michigan. [web site is silverseal.com]

dNa

OK, I finally re-read the ARP website. The studs will stretch and rebound, but they have not passed their yield point (re-usable). Man, I need to get more sleep, or get this birdie flying again, or both! Good looking SC Chris.

APR head studs are the way to go...they are stronger and reusable. In the past it was necessary to trim some of the short studs for exhaust manifold clearance. Now they have a set that fits perfect.

David

how do the head bolt sets from arp compare to the stud kit. Can the heads be pulled with the motor in the car? In other cars you cant lift the heads off because they hit the fender wells while guiding them off the studs. When i build my motor, i'd like to use studs or bolts from arp. I just dont know which is better.

I just used a set this past weekend. I really like the ARP studs, I got the Chevy 2.8L kit so they fit without trimming.

You can install the remove and install the heads with the studs in place, at least on a '94/'95 SC. Also the studs have an allen socket in the end of them. If they are causing trouble removing the head, you can use an allen wrench to remove the stud with the head in place.

i'am in the same boat as you and then some. i have a 90 with 92k and have the heads off, bought it from the orginal owner and it had just blown a headgasket. I just received my order from summit, two arp head stud kits, one tbird and the other is the chevy kit. the short studs in he chevy kit are shorter that the short studs in the tbird kit. I guess arp still has inventory out there with the "too long" short studs. I'am planning on using the chevy kit because i don't want to grind on my exhaust manifolds.
did you blow a headgasket, and if so are you replacing the bearings like some people recommend on this board? thanks, bob

I am not sure if you were asking me, but no I do not think I blew a headgasket. Even if I did blow a gasket, it didn't get any coolant into the oil to damage the bearings.

I blew out a heater hose, and the waterpump seals at the same time. I suspected the cooling system was seeing a lot of pressure from the combustion chamber. And since the engine has close to 100k I thought a new set of gaskets wouldn't hurt. Once I got the heads off though, I didn't see any gasket damage.

Regarding the T-bird stud kit, I think most people are grinding / cutting the studs shorter as opposed to grinding the manifolds.

Grinding or cutting the studs shorter is not a good idea, this will change the strength and stretch properties of the stud. The solution is simple, do not buy the Tbird kit, which for whatever reason ARP has not fixed, despite lots of feedback that half the studs are too long. Buy the Chevy kit, it fits perfectly.

I just used a set and they were the proper length from SCP. I have used the torque to yeild and the ARP`s are the way to go.

I'm sure SCP sells the chevy kit that Rob and Andy mentioned. I wish I had know about the chevy kit, because without the allen head socket on the end of the studs I have, it's a major pain to remove the long ones on the driver's side when taking the heads off.

David

[Well it looks like you already looked this info up, but I didnt notice until I was ready to submit this. No use wasting good info though.]

89psychobird said:

Between what they have said and what I have read online (not on SCCOA), torque to yield bolts are they way to go (if torqued properly). Due to the fact that Aluminum expands more that steel when heated, the stretch of the bolts always keeps an even clamping force between the heads and the block.

If the ARP studs don't stretch like the bolts do, wouldn't this cause a kot of stress on the heads of a hot engine and possibly crack the heads.

Click to expand...

I'm not a engine builder either, but I am a mechanical engineering student. Basically, the difference between the torque to yield bolts and the arp studs are that they are being brought to different parts of the stress-strain curve when installed (look here for an example: http://darkwing.uoregon.edu/~struct/courseware/461/461_lectures/461_lecture24/461_lecture24_pic1.gif)

The bolts are being brought into the plastic range, where the line starts to curve. While this stress hardens the bolt, you are putting the bolt into the upper stress limits with just the preload. With high combustion pressures the bolt moves closer to ultimate stress (if it exceeds Sut it will stretch very easily and soon break), and because it is in the plastic range its deformation is permanent. The bolt will stretch more easily than the studs but they will stay stretched, slowly eroding your seal. If you are having problems with excessive heat and pressure and need that extra stretching to keep from cracking a head, you are just using a bandaid and have other serious issues you need to fix.

The head studs are kept in the elastic range, where the line is straight. Assuming that the same torque is applied, the studs' stress-strain curve must be much larger (stronger than the bolt). The studs will not give as easily as the bolts, but they will give. And because the studs are still in the elastic range, the stretching is not permanent and the studs will shrink back to close to their original length and still keep a good seal. Plus the studs are reusable.

I already ordered some ARP studs for my headswap project .

-Travis

Anyone crack a head or blow a gasket with an ARP stud in there???

Yeah I have, and lots of other guys with studs have blown the head gaskets. But it didn't have anything to do with the studs.

David

Intersting to note and not mentioned is the difference between studs and bolts regardless of teh same material...I'll let someone else type that up being its late:O)...Also biggest failure with the factory bolts is failure to properly torque them. The old 1/4 turn trick is not very accurate

ok, some one with a real story... Dave, please tell us about it.

Mike, if you are referring to Dave's blown HG, the story is short and simple though it took a while to determine what was happening. Dave Chris Wise and myself had disgustingly poor surface finish on our blocks and used the MLS headgaskets during the engine build. The result of this was leakage past the headgasket due to the non conformity of the material to the rough surface. You MUST have a mirror like finish on the block and head deck surface for them to seal properly. For more detailed info, do a search under my user name and head gasket. One of these days I will get around to finishing the FAQ I started on this matter.

Paul

Yes what Paul said is correct and others with studs have blown gaskets, for other reasons like improper torque, or running excessivly lean.

The studs aren't going to stop you from blowing a head gasket, but they are reusable and a little stronger. I've had my heads off 3 or 4 times in the last two years, so I think they were a good investment.

David

That fits with my understanding as well.

The ARP bolts/studs play little to no role in preventing head gasket failure when compared with properly installed torque to yield bolts.

Instead, what you gain with the ARP bolts/studs is re-usability and perhaps a simpler method of proper installation.

It is my understanding that the tendancy to blow head gaskets on the SC is the result of a head design that doesn't allow for sufficient even clamping force to be exerted by the head bolts. Thus the heads become the weak link in the chain.

This can be good, and bad. Good in that the gasket blows rather than putting a hole through the piston due to a lean condition. Or the gasket blows rather than bending a connecting rod due to excessive detonation.

Thus I would imagine that TTY bolts are just fine for someone putting in new headgaskets and they don't expect to:

#1 - pull the head again
#2 - not follow the torquing instructions
#3 - race or otherwise push the car towards it's limits.

If you think you might pull the head more than once or plan on pushing the car to it's limits, ARP studs are likely a very good investment.