ARP L-19's...
 

Okay need some of the Fastner guru's opinions...

Tried searching but didn't find what I was looking for. If ARP is recommending 80ftlbs for these 7/16" L-19 head studs is there any benefit what so ever going 10-12% over spec to 88-90ftlbs?

Can this be done without stretching the stud and compromising the integrity of the studs thus giving a better/stronger seal?

I know many people, myself included, have "over" torqued the std. ARP studs to help provide a better seal or is this not really the case because of stretching the bolt and thus making it worse...?

A very possible result of over-torquing is the chance of pulling threads out of the block. I've done it on traditional small blocks at just over 65 ft. lbs. If you are working with an LS1 aluminum block and steel studs it could be a toss-up between pulling threads and stretching the stud. I'm betting that the aluminum will give up first although the length of the threads in the block might save the day. There should be no particular benefit to stretching the fastener past its recommended limit.

Good luck with this problem.

With the length of the studs threaded into the block I don't see an issue of pulling out the threads of the block. I have actually had a std. ARP stud snap in half because of it not resting on shoulder of stud but rather, looking at end of stud, bottomed out during torquing and it broke in half...

So nobody else can give me any more advise???? Guess I'll stick with my original plan and go to 90ftlbs with these which is about 12% over torque spec...

I would talk with ARP first.

Most fasteners have a certain ammount of stretch, which is why you have so many OEMs going witha torque angle setup rather than just a torque spec. You want the fastener loaded and "stretched" as it will do better than a fastener then is not loaded properly.

When you use a rod bolt stretch gauge you will find your torque specs all over the place in some cases, but the fasteners loaded equally.

I use the stock diameter L-19 head head studs. ARP told me to put them at 96ft-lbs. They have been on and off a few motors, never a problem.

Why in the world do you need to over tighten the bolts? To get a better seal for a High Boost application? I think ARP has done a LOT of testing regarding their fasteners. I would go by what ARP says...

Thanks for the info Jarrod!


Thats what I needed to hear. I was told, from the dealer in CA I bought these from, 80ftlbs for the stock size L-19's which I thought was pretty low. I feel more comfortable now spending what I did on these L-19's compared to the standard ARP's and not getting much more torque...I'll give ARP a call too.


It's been common practice for ALOT of builders to over torque the specs on alot of head fastners...not quite sure why either but its done...

Usually, the given torque palces a load on the stud that is 75% of the yield. So if the fastener yields at 20,000 lbs, the torque is designed to give a clamp load of 15,000 lbs. The problem, though, is that torque is a very bad way to gauge the clamp load placed on the fastener. 85-95% of the torque is used to overcome friction, so only 5-15% of the torque actually goes into the clamp load. The problem is that a minute change in friction makes a large change to the clamp load actually applied. Everything from type of oil used, how much oil used, temperature, humidity, and like my old professor used to say, "even the phase of the moon," all affect what the end clamp load will be. If you torque higher than what arp recommends, you may overshoot and yield the fastener or come far short, there is no way to know. If you need more clamp load, you safest bet is to go to a 1/2 stud.

Al

That is exactly why he was wondering. he is running about 18 psi right now. Dennis, I would think that you would not run into problems with the stud unless you bottomed it out. i would have to believe that ARP designs a bit af a safety factor into their studs. With what I have heard about the L-19s you would pull the threads in the block before you snapped the stud. FWIW I would try maybe 85 first and then go from there. With the studs being so much stronger, you will be applying a much higher percentage of the increased torque to actually pushing the head down than stretching the stud. JMHO. Good luck.(edit) Nevermind, I see you already have the answers!! :eyes:

Al great information!! I realized a very large part of the torque is to overcome friction. What I didn't realize is that it was 85-90%. Thank you...

Thanks Keith...I'll prob shoot for 90ftlbs using the ARP lube provided with the studs and go from there.

Also, I like to put a thin coat of the ARP lube on the entire stud to prevent any corrosion with this type of material.

So you are recommending that DJ's99SS cut down the "safety factor" by putting the clamping load very close to the failure point? I strongly advise NOT doing that.

The only was a stud or bolt creates clamping load is by stretching. Any stud that can provide 275,000 psi necessarily has a "stress-strain" curve that is very steep and peaky with not a lot of room between yield point and failure point. Metal can't be convinced by logic nor bovine scat to act other than how Mother Nature intended. I'd ask ARP for their advice and follow it to the letter. They are the ultimate "fastener gurus" in this case.

A couple of analogies:

1) A race tire vs. a street tire: The race tire provides lots more lateral (cornering) load with increasing slip angle, but it has a very abrupt break at the limit. Street tires have a more gradual slope and a smooth peak so that you get a "soft" rather than "hard" limit. L19 studs are certainly in the "race tire" category.

2) Peaky hp curve vs a less steep hp curve with a soft peak which just holds on is a similar example. That's fairly easy to visualize.

As was suggested earlier, if you need more clamping load, go to a bigger stud. It's likely that the aluminum head is deflecting between the studs and not lifting off the block in the areas around the studs.

My $.02

Thanks for all the info...I'll post what ARP suggests for me to do.

Just had a course in ARP engineering from a Tech at ARP...All I can say is Damn there are some pretty intellectual peeps over there. I was sent to the "specialty" fastner divison of ARP in another location so here's the scoop.

The tech is actually getting back with me on the exact clamp load needed for our all aluminum motor/head set ups using the ARP L-19 head studs. What I never wrapped my tiny little brain around was how much our all aluminum motor/heads expand. We're looking at almost twice as much expansion during heat cyles than a standard iron block/head motor. This must to be considered when figuring the static torque of our head studs to compensate for the expansion of the aluminum...

In other words we need to compensate for the expansion during the torquing process to allow for additional yield of the head studs. An example would be if a fastner had a 25,000 psi yield we would, because of the expansion of the aluminum, would have a 18,000 psi static clamp force to compensate for the expansion...we need to be looking at around a 70% static clamping force of the full yield of the fastners.

I'll post more info on the exact figures ARP gives me as soon as I get them...It looks like the L-19's are 20% higher in strength compared to the standard ARP's. 260,000 psi compared to 190,000 psi.

We've used the L19s at 81 ft pounds on aluminum and they worked very well so far.

Thanks Eric!

Chris @ ARP just got back with me and it looks like 85ftlbs. is the magic number. He's checking a few more figures and will get back with me just to make sure. If ALL the Vendors would be this responsive, polite and caring the world would be a better place... :jest:

What it sounds like to me is that the increased expansion rate of the aluminum in effect further preloads the fastener (in addition to the torque already applied) and carries it closer to the yield rating. Am I correct in this assumption? Stroker, now that you put it like that I guess I agree with you. :jest:

I think someone said 85 ft/lbs already :) jk Even a blind squirrel finds a nut every once in a while. :jest:

You are correct sir...

Damn Keith...you lucky bastad... :) Becareful when you go looking for those nuts... :eek2: