What is the difference (besides massive price) between stock GM head bolts and ARP hex head studs?

Just wondering??

Curtis

 

head studs are re-usable, stronger and you never have to take them out of the block again. Stock head bolts are ok, if you dont ever plan on taking the heads off the car ever again. ARP's are just a little added extra insurance IMO....

 

Curtisad -you said ARP head studs....not bolts right.
Hastingsrj - ARP head studs same as ARP head bolts?

 

the GM head bolts are a torque to yield style bolt. this means that when properly installed, they are tightened so much that the bolt stretches. if removed, these bolts must be thrown away, and new ones used.

the ARP headbolts and headstuds are a conventional bolt/stud that can be reused. and are considered stronger then the GM ones.

headstuds are preferred by race engine builders over bolts because they thread all the way into the block, using all of the block threads. and the torque specs read more accurate because the nuts at the top, near the torque wrench, are the only thing being read... you dont have a long bolt and alot of friction from threading into the block as you torque it.

the downside to headstuds is that they must all be removed from the block before you can get the heads off when the engine is in the car... if you're working on the engine outside the car, you can leave them in.

 

Another advantage of studs- you're not grinding out the threads while you're mashing them into the block while torqueing. That saves a lot of wear on the block threads, so when the joint is complete, there is a better fit between block and fastener.

Also, all threads are engaged and fixed in the block during the entire torqueing process, so stretch along the length of the threads remains uniform.

Finally, studs have a finer pitch yet you torque them to the same torque value- which results in about 42% greater clamping force. That will help keep your seal when dealing with higher combustion chamber pressures (such as when boosting or using juice).

 

I did not know this. I thought the heads could be removed with the head studs in place on the Corvettes and the Fbodys.

John

 

I was debating between the two too. I am glad I made the decision to spend the money and get ARP 12 pt head studs. I've had those heads off and on so many times, checking PtoV, squish and I don't that I would have liked torquing the TTY bolts into the block each time.

 

Can you get the heads off with the motor on the car?

 

 

I'm the wrong person to ask. I'm heading towards two years working on my conversion

 

I saw where someone asked the question about cycling the torque on bolts and i hadn't seen this before.
Using a Torque Wrench



If the stretch method cannot be used in a particular installation, and the fasteners must be installed by torque alone, there are certain factors that should be taken into account. ARP research has verified the following “rules” pertaining to use of a torque wrench:

1. The friction factor changes from one application to the next. That is, the friction is at its highest value when the fastener is first tightened. Each additional time the fastener is torqued and loosened, this value gets smaller. Eventually the friction levels out and becomes constant for all following repetitions. Therefore, new fasteners should be tightened and loosened through several cycles before applying final torque. The number of times depends on the lubricant. For all situations where ARP lubricants are used, five cycles are required before final torquing.

2. The lubricant used is the main factor in determining friction, and therefore, the torque for a particular installation. Motor oil is a commonly used lubricant because of it’s ready availability. If less friction is desired in order to install the fasteners with less torque, special low friction lubricants are available. With special lubes, the required torque can be reduced as much as 20 to 30 percent. It is important to keep in mind that the reverse is also true. If the torque value has been specified for a particular fastener on the basis of low friction lube, installing the fastener with motor oil will result in insufficient preload; the torque has to be increased to compensate for the extra friction caused by the motor oil.

3. Surface finish is also important. For example, black oxide behaves differently than a polished fastener. It is therefore important to observe the torque recommendations supplied with each fastener.

NOTE: It is possible for even the most expensive of torque wrenches to lose accuracy. We have seen fluctuations of as much as ten (10) foot pounds of torque from wrench to wrench. Please have your torque wrench checked periodically for accuracy.

 

yes..you can get them off without taking the studs out.

 

so the consensus is ARP head bolts.....12 pt. ??

 

That's what I have for my H/C install.

 

You dont have to pull them out on vettes! Hehe.

 

if your just N/A....then the GM headbolts are just fine. not to mention alot cheaper.