I was going to get my Cast L98's equiped with ARP studs and retain my stamped steel rockers and nuts until I read ths "These rocker arm studs are designed to be used with Perma-Loc adjusters (not for use with OEM-style, self-locking nuts). " WTF Is up with that? I dont want to spend another 50 bucks on their nuts. Any idea why this would be?

 

a good way for ARP to sell more parts, other than that it seems to me OEM parts would work

 

The ARP studs will break while backing off a stock lock nut. Snap right off, at the bottom of the lock nut. It's not as bad if you back off the lock nuts REAL SLOW. Don't ask me why. But I broke a handful of them once, maybe 3 or 4 out of 16, trying to tear down a motor built like that. Sure surprised me.

 

So your saying the pressed in Factory studs are stronger then arp bolts?

 

Where did that idea come from? I don't see where I said that anywhere.

The ARPs broke off clean and sharp, like glass that's been cut with a glass cutter. (Glass is very very hard also....) I suspect it was something acoustic. The nuts made a strange squeeking noise as I backed them off, and the stud metal was so hot after it broke, you couldn't touch it.

I have no particular explanation for it. Maybe I just had some bizarre quantum mechanical effect concentrated in my corner of the universe that can't be duplicated elsewhere by smarter people than me. Feel free to try it yourself, and make sure you come back and tell everybody what happens.

 

That idea came for common sense. If the ARP's broke, one would think that the stock ones would break as well. So basically once they are on there they can never come off unless you break the studs.

 

Well, not quite; rather, think of it as, once they're on there, there's a significant chance that when you do take them back off, they will break their studs. Removing the nuts slowly lessens the risk. Perhaps there's a threshold of "nut backing off speed" below which no damage or excess stress occurs in the stud; I don't know that.

I can take a sheet of glass and roll a glass cutter over it, and it will snap in half. I can take a sheet of rubber and run the same glass cutter over it, and it won't snap in half. Does that mean the rubber is harder than the glass? No, in fact it means the exact opposite.

Richmond drag-racing gears for 7.5" rear ends for instance are made not to break under racing usage. Factory gears break when raced. The reason the factory gears shatter, is precisely because they are harder. I suspect the ARP stud deal is similar. The lock nuts do something to the stud that the softer factory stud metal can withstand; but the harder ARP metal can't. You give up one property in order to gain on some other property.

You're right, it does seem a bit counter-intuitive; but, if you think about it a little more, once you realize that metallurgy is always about compromises, it makes pretty good sense actually.