Undercut head studs....when needed?

Per ARP:



You will also note that ARP® offers specially undercut studs for several engines. This procedure (done only to the shorter studs) more equalizes the “stretch” of both studs, which makes for a more consistent clamping force—and one that compensates for head gasket compression when the cylinder heads are installed. This helps prevent blown head gaskets, and assures optimum engine sealing!



Unfortunately, ARP tech support isn't all that helpful regarding when they recommend stepping up to undercut studs from standard studs.

To the experts out there, how extreme must an application be to justify running them in a forced induction motor? Are we talkin' only in motors like Brady's (www.turbocharged.net) or in any motor where cylinder sealing (sans o-ringing) is a critical issue?

Note: this is with the same top end as the motor in the sig, but with lower CR and a maxed T-Trim blower.

TIA

Kinda curious myself. What IS the difference between standard head studds and undercut ones??

I mean, the price difference is only about $35, so other than saving a couple of bucks, is there any reason to NOT use the undercut studds?

joe- the diff is stated above :)

I would go with undercut period. if you feel you need studs, get teh under cut ones.

Originally posted by JordonMusser
joe- the diff is stated above :)
Reading is fundamental........and I'm fundamentally blind!

the reason to undercut the body of the stud is to provide more stretch in the body when torqued so when under load the threaded end of the stud in the block doesn't stretch and fail, usually a mild undercut works well to balance the two out, alot depends on the material used and the amount of torque used on the stud. sorry that's about the best I can explain it. If you have stretched studs especially in the threaded section an undercut is the next thing to do, or go to a bigger diameter stud.

Kinda makes ya wonder how engine builders got/get by with the standard stuff. Hmmm, must be a group of special people. But then again, maybe there was just a good arm to brain link. Hmmm. (shrug)

arnie- most "engine builders" are ID10Ts. Most couldn't pass a college level(or HS for that matter) physics class, or materiels class. they really don't know what the **** they are doing. they just know that if they put a bolt in there, it probably won't blow up.

I know engine builders that reuses stock head bolts on performance build ups. does it hold? most of the time.. yea. would I do it? er.. no :)

Can you get the heads off an 4th gen with head studs and the engine in the car???

Originally posted by Blownbird355
Can you get the heads off an 4th gen with head studs and the engine in the car???

All the new ARP stuff is "broached," allowing removal of the studs with a hex key. Even if this wasn't the case, it would only take a couple of hours to drop down the front subframe/motor anyhow for extra clearance.

Thanks for the tips thus far:)